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shee si ~ f WILLIAM H. DALE ew i | f SECTIONAL LIBRARY | ei DIVISION OF MOLLUSKS
VELIGER
A Quarterly published by CALIFORNIA MALACOZOOLOGICAL SOCIETY,
Berkeley, California
Volume 12
July 1, 1969 to April 1, 1970
Page II
THE VELIGER
Foreword to Volume 12
IT HAS BEEN SAID that everybody talks about the weather but nobody does anything about it. The same thing could be said about inflation. We are all painfully aware of its consequences. Yet, we at the Veliger think that we are doing our share — and perhaps a little more. In spite of the continually rising cost of paper, printing and postage, over the years we have effectively lowered our prices. Our first volume could be obtained at that time for $1.-; it comprised 40 pages and had no illus- trations. The present volume was sent to our members for their dues of $8.- — a rise in cost of 800%; but the volume comprises 488 pages and 64 plates, 5 of them in color — an increase in page numbers alone of over 1200% with the added bonus of the many fine plates.
When the dues and subscription rates for the coming year were set, very careful consideration was given to the present inflationary trends. But despite these pressures, the decision was made to keep the dues and subscription rates at their present low level. This was done not without the hope that our members and subscribers would assist us in our effort by helping to increase the number of members and subscribers. We feel that no one need hesitate to recommend the journal to his conchological and malacological friends. It also will assist us to keep our overhead expenses at a minimum if members will pay their dues promptly as well as advise us in proper time of address changes, thereby making all our financial resources available for our primary goal — the continued pro- duction of our journal.
That it has been possible to continue producing our journal under the ever more stringent financial conditions has been due mainly to the selfless devotion of a very few individuals. Though they wish to remain unnamed, your editor would be remiss if he were not expressing his deep appreciation to each and every one of them.
Sincerely, Your Editor
Vol. 12; No. 4
Vol. 12; No. 4
TABLE OF CONTENTS
A bibliography of the biological writings of PHP PEARSALL CARPENTER. BISGEINIEMV- | COAN) | i seee eeh ns ferret tne esc 222 Additional bathymetric and locality data for some opis- thobranchs and an octopus from Santa Barbara County, California. RICHARD S. LEE & PATRICK BROPHY esses 220 A list of recommended nomenclatural changes for Mac- FaRLAND’s “Studies of opisthobranchiate mollusks of the Pacific coast of North America.”
RIGETARDWATIROUT ER: enna ve dol ee. 371 A mechanical shell washer. JacgueELin N. MILver & Cart L. HUBBS wee 379
An annotated bibliography of references to marine Mol- lusca from the northern state of Sonora, Mexico. CS AROMISKOGL UND etd ent can ele cece 427 Anatomical notes on the mactrid bivalve, Raeta plicatella Lamarck, 1818, with a review of the genus Raeta and related genera. Harotp W. Harry An ecological study of valley-forest gastropods in a mixed mesophytic situation of northern Kentucky. BraNnLey A. BRANSON & Donan L. BatcH_............ 333 A new species of gastropod (Fissurellidae, Fissurisepta) from the eastern North Pacific Ocean.
LASS JM UGHLE, CLONZSceceeee e e 24 A new species of Helminthoglypta from the Mojave Desert. WAT TER DB SIVIEE DER titer ochre aia cs Bh 275 A new species of Muricopsis from West Mexico. GerorceE E. Rapwin & ANTHONY D’ArrItio ............. 351
A note on the chromosome number and interrelationships in the marine gastropod genus Thais of the United States Pacific Coast.
MuzamMMiL AHMED & ALBERT K. SPARKS ( oeeccccson 293
A note on the opisthobranchs of Santa Cruz Island, Cali- fornia.
STEVEN MSONG ti) chb ne ie Sanit SU Oe Od seat rah ets 232
A possible “defense” response in a commensal polychaete. Ronatp V. Dimock & Joyce G. DimocKk_ ...........0...
A report on the feeding of Dendronotus iris on the antho-
zoan Cerianthus sp. from Monterey Bay, California.
Done RAWOBBERG pate ee eet Ae 383 A revision of the eastern Pacific Ovulidae. @RAWEORDRING CATE Hee ee een ee ee ee 95
Ascophyllum nodosum: a source of exotic invertebrates introduced into west coast near-shore marine waters.
RICHARD MU MIBEER 2 eet ee AE 230 A simplified vacuum apparatus for collecting small nudi- branchs.
ER OEIER MAN BUEAIGNEY 0 cscs ond wate. Memeo eee 142
THE VELIGER
Page III
A supplement to the annotated list of opisthobranchs from San Luis Obispo County, California.
IRIGEARD/ AW ROLLER eerie tens neat mse eetenat 482 A three-dimensional representation of measurement data. PAu CHANLEY & W. A. VAN ENGEL sscsecensenens 78
Cadlina modesta: a range extension, with notes on habi- tat and a color variation. IANS s BERTS GH) Sige aortee ae anni neg eterna 231 Cargoa cupella, new genus and new species of nudibranch from Chesapeake Bay and the generic status of Okenia Menke, Idalia LrucKart, and Idalla ORSTED. RosAauie M. Vocet & LEONARD P. SCHULTZ... 388 Concerning the validity of the new species of Paravitrea proposed by BRANSON & Batcu (1970). Lanpon T: Ross & LAWRENCE C. ABELE oases 484 Correlation of radula tooth structure and food habits of three vermivorous species of Conus. JAMES NYBAKKEN sien eGt seme ontd ooh ose 316 Current paleontological investigations on Cenozoic marine mollusks of the west coast of North America.
WarreN O. ADDICOTT & SABURO KANNO © erettsnsssessscsee 135 Cuttlebones on the beach at Galveston. Harowip W. Harry & SELMA FE SNIDER oivssscscsssssnn 89
Cyclostrema miranda BARTSCH, a synonym of Tornus sub- carinatus (MonTacuU). DONALD ERG: MOORE hye een rs See ar een ee 169 Cypraeidae of the Red Sea at Massawa, Ethiopia, with a zoogeographical analysis based on the ScHILDERs’ regional lists. MiCSonve Le. P RUEBUSH MR a ss inet. cautndad 201 Descriptions of a new genus and eight new species of eastern Pacific Fissurellidae, with notes on other spe- cles. JAMES DEOMGICEAN, «occ .cccetacatarian. tani lech eens 362 Escape response of the sea-anemone Anthopleura nigres- cens (VERRILL) to its predatory eolid nudibranch Herviella BABA spec. nov.
RU SIROSIN Mra Sees oe tear a2, ores 74 Escape responses of three Indian molluscs.
ANID VANSELT, 60 cl 0 aed ate es al ee 157 Five new species of Terebra from the eastern Pacific.
Mwita BratcHer & R. D. BURGH tite ident 295 Identification of the feeding types in the genus Conus
LINNAEUS. (CUE BIGING ee ae esate ean ae oe ae 160
Levels of spontaneous electrical and acetylcholinesterase activities during aestivation of the Indian apple snail, Pila globosa.
P Muraut Mowan & P. Murari KrisHna Dass 37
Macoma (Psammacoma) pulleyi, a new clam from Louisi-
ana. PAUL Ss BOVER ojo siocssccsntsicrsst cn cned ees nee eh ee 40
Page IV
Malacological applications of scanning electron micro- scopy. I. Introduction and shell surface features. FAA s SOLE Ms scscentaastsnsriiclassncean aie ae ere een 394 Marine fouling and boring organisms in Monterey Harbor — II. Second year of investigation. Ee CHApERTIE ries Oe. See ee eae 182 Mimicry of the gastropod Mitrella carinata by the am- phipod Pleustes platypa. JUrESEM@ CRANE: fre SS ae Se ee ee 200 New range for Mopalia hindsi recurvans BARNAWELL, 1960.
GLENN BurRGHARDT & LAURA BURGHARDT oe 229 New species of Panamic marine gastropods. (AMESMETS Melia Nese ese eee eee 310
Notes on the deep water calliostomas of the Panamic pro- vince, with descriptions of six new species. AMES EL MCLEAN: ate ee eee 421 Notes on the egg capsules and larval development of Conus purpurascens BRODERIP. PANES WINVBAKIKE Nis, 2208 Dees Binh paar eB ee 480 Notes on the Mitridae of the Eastern Pacific II — The genus Thala, with the description of a new species. GALE Gr SPHONI ga, bike at oe neha 2 eae We 84 Notes on the collection of Tritonia festiva (STEARNS, 1873) from the seas of Japan (Gastropoda: Nudibranchia). KIKUTARO BABA. ci dea, ee eee ee 132 Observations on the anatomy and biology of two Califor- nia vermetid gastropods. MIGHAET| Gi HAD ETER D2 etieetee eis ora een 301 Observations on the reproductive biology of the Kellet’s whelk, Kelletia kelleti. RIGHARD!]; ROSENTHAL 3 S22 S00) ee eee 319 Observations on the tentacles of Vaginulus borellianus Co tosl. ARISTEO)/RENZONTO encode oe eee 176 Occurrence of a rare squid, Chaunoteuthis mollis APPELL- 6F (family Onychoteuthidae) in the Indian Ocean. KN ANESIS( 3th ein ne eee 290 Occurrence of the sacoglossan opisthobranch Hermaea dendritica ALDER & HANcock in New England. Kerry B. CLarK & DAVID R. FRANZ oresmsssssnseseinaneen 174 On Pseudopythina rugifera (CARPENTER, 1864). WaLter NarcHioiet ha aioe eee ee 43 Observations on Pervicacia tristis (DEsHayES, 1859) and a comparison with other toxoglossan gastropods. WRB RUD MIAN ups hie ce oot ea a 53 Occurrence of the cephalaspid Philine sinuata (Stmmp- SON ) in southern New England, with a discussion of the species. DROP RANZ {EK S GUAR, 1.2.00 200 INE iad Bhd 69 On CEerNoHorsky’s designation of a lectotype for Murex mancinella LINNAEUS. Haroip E. Vokes
THE VELIGER
Vol. 12; No. 4
Panamic sites and archaeological mollusks of Lower Cali- fornia. LAWRENCE HL. FELDMAN, cieccmcscecneismnsrennnneent 165 Pleistocene symbiosis: pinnotherid crabs in pelecypods from Cape Blanco, Oregon. Victor A. ZULLO & DUSTIN D. CHIVERS 0 oun 72 Population characteristics of Protothaca staminea (Con- RAD) from Mugu Lagoon, California.
Rona_p R. ScomptT & JOHN E. WARME on 193
Range extension of Tjlodina fungina in the Gulf of California.
James W. McBetu « R. David BOWLUS nese 229
Range extension of Tochuina tetraquetra (PAuas, 1788) to Hokkaido, North Japan (Gastropoda : Nudibranchia). KIKUTARO. BABA j jasgeincencithgien tee 134
Range extensions for Acanthodoris hudsoni MacFarLaANnD,
1905, and Onchidoris bilamellata (LinNaEus, 1767). Gary R. McDONALD: eiscioctiecenniene ee 375 Relative growth patterns of two west coast squid (Gona- tus fabricii and Gonatopsis borealis). Larry 'T. SPENGER) ses:ecdtectindinecs Ree eee 171
Remarks on the taxonomic placement of Purpurellus
JoussEaumME, 1880, with the description of a new species. WILuIAM K. EMERSON & ANTHONY D’AttTitio —_—«:145
Report on some abnormal chitons from California and
British Columbia. GLENN BurGHARDT & LAURA BURGHARDT ou... 228
Reproductive cycle of the coot clam, Mulinia lateralis
(Say), in Long Island Sound.
ANTHONY CALABRESE) sencscisncardarhes-ca eee 265 Russian contributions to malacology. KENNETH J. BOSS. 222 e2 A ae cane 226
Seasonal gonadal changes of adult oviparous oysters in Tomales Bay, California.
Cart J. Bere, Jricu eee A 27 Spawning notes V. — Acanthina angelica I. OLpRoyp, 1918 and Acanthina lugubris (SowerRBy, 1821).
FAY HENRY, WOLFSON Ges. eenen 375 Supplementary comments on deep water Volutidae from the South China Sea and South Africa.
HARALD) A. [REHDER "vs. cecchidank destin be ee 415 Technique for extraction and mounting of gastropod rad- ulae. E GrorGe, Ey RADWIN( once diecsceinaseeeeenne ae 143 The cowrie species living at Guam. CRAWEORD! Ni (CATE Goce eee 120
The distribution and ecology of sub-littoral species of Macoma (Bivalvia) off Moresby Island and in Satel- lite Channel, near Victoria, British Columbia.
R. M. Dunnit « D. V. Eis
The eastern Pacific cowries.
CRAWFORD. IN. (CATE: 22... cceeentes 28 ae eee, 103
Vol. 12; No. 4
The effect of wave impact on some aspects of the biology of sea mussels.
Jap cu Ei EVARGER) Geet 2 mere case ojo wane Meant 401
The endodontoid land snail genera Pilsbrycharopa and Paryphantopsis.
JUIN, SOOTY. Creat cee ch uc art Men ee ee 239
The systematics and some aspects of the ecology of the genus Dendronotus. GORDON VAHROBIDETARD: aca Sot fishaseselicctescnedssausimtne 433 The west American species of Murexiella (Gastropoda: Muricidae), including two new species. IBMT AEA SAVOKIES! | ccttrnthe termine niet niu tae 325 Three new species of muricacean gastropods from the eastern Pacific. WiiuaM K. Emerson & AntTHony D’Attitio 270 Two new Epitoniidae from the Galapagos Islands. DEVE NAPING YU S EUAN IE | cet actclaccct Oh Peart sgcncssscerisetessseesa 330 Two new species of deepwater bivalves from the Carib-
bean Sea. EVAR OV DBE MeN OKE Sie ite Mustaine ed adh ean lie al oni 357 Two new species of Galapagan turrid gastropods. WILuIAM K. EMERSON & GeorGE E. Rapwiw_........ 149
Two new species of the genus Caldukia BuRN & MILLER, 1969 (Mollusca: Gastropoda: Opisthobranchia) from New Zealand waters.
VET EVAR CMMNITE EER) ites ene oe le bi ua dha 279
Uptake of sea water into the fluid spaces of the proso- branch gastropod, Acmaea scutum.
IT emE PAVE BBE Rage nite crc ns 0, Part ceetnsuels cel es 417
AUTHOR INDEX
ABELE, LAWRENCE G. see Ross, LANDON T. & — AppicoTt, WARREN O. & SABURO KANNO AHMED, MuZAMMIL & ALBERT K. SPARKS J\SSIGHOH CI ANG) DS, ae IN ae oe Mec re ee Basa, K1KUTARO BErc, Cart J., Jr. IBERTS CHa EVANS) )cnnee nese BLEAKNEY, J. SHERMAN Boss, KENNETH J. Bow us, R. Davin see McBETH, JAMES W. & —
BOYER PAU INS ethene Men ten oe a a eae 40 BRANSON, BranLey A. & Donatp L. BatcH_.......... 333 BRATCHER, TWILA & R. D. BURGE occcssssssssssnsussssssssntsns 295 Bropuy, Patrick see Ler, RicHarp S. & —
Burcu, R. D. see BRaTcHER, TWILA & —
BuRGHARDT, GLENN & LAURA BURGHARDT ........ 228, 229 BurGHARDT, LAuRA see BURGHARDT, GLENN & — (CATABRESE VAINDHONY 9) tees freon i ua ins Aad L 265
CATES GRAWFORDYNS; Shot. Se OoNLO3S a al20
THE VELIGER
CHANLEY, PAUL & W.A. VAN ENGEL rcsmssssssmssssssnsasssseee 78 Curvers, Dustin D. see ZULLO, Victor A. & —
CiarK, KERRY B. & DAVID R. FRANZ rvsssssssssssssssssneen 174 Crark, K. see FRANZ, D. R. & —
(OLOVAING , VERO SSI VG ce eee cect reer peer renee crmreteecerats 222 Cowan, Ian McT__.............. 24
Crane, Jutes M., Jr. 200
Dass, P. Murat KrisHNna see Mouan, P. Murai & —
D’Attitio, ANTHONY see EMERSON, WILLIAM K. & — see also: RapDwin, GrEorcE E. & —
Dimock, Joyce G. see Dimock, Ronatp V.
Dimock, RONALD V. & JOYCE G. DIMOCK oeeeecsesnsine 65 ID) einRpacses IS, IML CE LDS WE OVS) ert eromeemnpermeemrenoreremmee 207 DU SHANE, SELELEN set sisstafeoscicescsasissvasectisiatantictewnssssmtaanots 330 Exus, D. V. see DUNNILL, R. M. & —
EMERSON, W. K. & A. D?ATTILIO oivcescsssussssssnsinnee 145, 270 EMERSON, WILLIAM K. & GEorGE E. RADWIN esmeese 149 IBELDMANRICAWREN CE sbi) ee eesreenne nn nnn ee see 165 omnes PaRUEBUSH eee eae 201 BRAN ZI Rese KCI CEARK), ; coer ni ee ee 69
Haverue, E. C. HaprFietp, MicHaet G.
LARGER Je Rete ater em meres Nestea. es at CAE 401 PARRY TARO ED. Wi crises ies Ue ee Ee ae ea 1 Harry, HAROLD W. & SELMA E SNIDER oovssssssssessssssssnseeee 89
Husss, Cart L. see MILter, JAcQUELIN N. Kanno, SABuRO see ApDICOTT, WARREN O. & — LEE, RICHARD S. & PATRICK BROPHY ( osscssssssssssssussssns 220 1 GY o.Y Ge OD Date etre eet EONG SO TEVEN Po) |. ciseteteece teeta saree accra eareines McBetH, James W. & R. D. Bowtus McDona_p, Gary R............ IMGIERAIN SDJ AMES#EN: cha cnren meee canaane MILLER, JACQUELIN N. & Cart L. Husss Mier, MicHaet C............ Mitter, RicHarp L. ....... Miter, WALTER B. Mouan, P Murat & P. Murai KrisHNa Dass ..... 37 Moore, Donatp R. NARCHI, WALTER ..ececos 43 INESISHKESNe) cecsicesecnnsann 290 NYBAKKEN, JAMES Rapwin, GrorcE E. see also: EMERSON, WILLIAM K. & —
143
Rapwin, GrEorGE E. & ANTHONY D’ATTILIO ocecsecscs 351 IREHDERWEVARALD IA cossetiead deccssane ueccsne enn 415 IRENZONIGP ARIS TRON pester ee ie RoBILLIARD, GorDon A.
IROLEER RICHARD) Ramer tele
RosENTHAL, RicHarD J. Rosin, R. IRUDMANEA Wile es ee ie SEE ee ee een a 53
Page VI
THE VELIGER
RuesusuH, L. P. see Fon, T. C. & —
SCHMDDT, RONALD R. & JOHN E. WARME eesti 193 ScHuLTz, Leonarp P. see RosALIE M. VocEL & — SKOGLUND,; CAROL 11h tea cee ee eee Meeeelinoneree 427 SNDDER, SELMA F see Harry, Harotp W. & —
SOBEM: CALAN fk: cee tet a, 1) (enum elas 239, 394 SPHON, (GALEN Gi), 22 ee. eee eee ee ea 84 Sparks, ALBERT K. see AHMED, MUZAMMIL & — SPENCER CARRY Ay ee Cee 171 Van ENGEL, W. A. see CHANLEY, PAUL & —
Vokes sEinaiiy He ten hee ccna ee 325 VoGcEL, Rosauiz M. & LEonarp P. SCHULTZ. .............. 388 VOKES; HAROLD) Bier Boa. eee ie ae 357, 368 WarME, JoHN E. see ScummpT, Ronatp R. & — WEBBER HEHE ih AUR er ee Oe a ene an 417 WoBBER}: Dony. RY hhh. ga a Oe 383 WOLFSON) PAY HENR Yarn ou eee wee ee 375 ZuLLO, Victor A. & DUSTIN D. CHIVERS (ovine Wi2
Vol. 12; No. 4
VELIGER
THE
A Quarterly published by CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC. Berkeley, California
VOLUME 12 July 1, 1969 NUMBER I
ConTENTS
Anatomical Notes on the Mactrid Bivalve, Raeta plicatella Lamarck, 1818, with
A Review of the Genus Raeta and Related Genera. (20 Text figures) Haro.p W. Harry
A New Species of Gastropod (Bissrelndae: Rasurieniayy far the Basen North
Pacific Ocean. (3 Text figures) Tan McT. Cowan
Seasonal Gonadal Changes of Adult @uiesraue Gystersh in Glomale: Bay (Californie:
(Plates 1 to 3; 1 Text figure) Cart J. Bere, Jr.
Levels of Spontaneous Electrical and Aceurleholinestsrase INctivities durae Nestiva-
tion of the Indian Apple Snail, Pila globosa. (1 Text vee P Murari Monan « P Murat Krisuna Dass
Macoma (Psammacoma) pulleyi, a New Clam from Tous (2 Text eure)
Paut S. Boyer
On Pseudopythina ueiete (Canesten, 1864) (Bivalvia). Gl Text fegres)
Water NarcHI
Observations on Pervicacia tristis Gieerneee 1859) aaa a Gonpaneen cain oer
Toxoglossan Gastropods. (5 Text figures) W. B. RupMAN 6 Aue en pniee ae Nana A Possible “Defense” Reeponseli ina s Commmencal Polychacte (Plate 4)
Ronatp V. Dimock « Joyce G. Dimock
Occurrence of the Cephalaspid Philine shed Greco it in Souler New enelandl
with a Discussion of the Species. (8 Text figures) D. R. Franz « K. Ciark
Pleistocene Symbiosis: Pinnotherid Gens in Weelenypods) fara cone Bianco! orear
(Plate 5) Victor A. ZuLLo « Dustin D. CHIVERS
[Continued on Inside Front Cover]
7 a ra pre ee
Distributed free to Members of the California Malacozoological Society, Inc.
Subscriptions (by Volume only) payable in advance to Calif: Malacozool. Soc., Inc.
( gut 24 1969
Volume 12: $18. Domestic; $19.- in the Americas; 19.50 in all other Foreign Countries
Single copies this issue $12.-. Postage extra.
Send subscription orders to Mrs. JEAN M. Carte, 12719 San Vicente Boulevard, Los Angeles, California 90049. Address all other correspondence to Dr. R. Stouer, Editor,
Department of Zoology, University of California, Berkeley, California 94720 Second Class Postage paid at Berkeley, California
R A R ES -
ConTENTs — Continued
Escape Response of the Sea-Anemone Anthopleura nigrescens (VERRILL) to its Predatory Eolid Nudibranch Herviella Baza spec. nov.
Rev ROSINSS ee =), SESE! ee Heer amen Al A Three-Dimensional Resretentaron of ‘Measurement Data (4 Text figures) PauL CHANLEY & W. A. Van ENGEL ee ‘ dey Bent eer th nether 7S Notes on the Mitridae of the Eastern Pacific Ir - The Gann Thala, with the Description of a New Species. a 6; 2 Text ga I nee Gate G. SPHON. : : : a) Soa ee Od Cuttlebones on the Beach at Galveston! (3 Text figures) Haroitp W. Harry & SELMA FE SNIDER eee Suanaro aes!) A Revision of the Eastern Pacific Ovulidae. (Pate 7 to 10; et Maps) CrawForpD N. Cate. . . 2 het Es The Eastern Pacific Cowries. . eiates) It to 15; 3 Maps) Crawrorp N. Cate . . Sf cs ee sent epee EOS The Cowrie Species Living at Guan (Molluses : (Grsttopoday, (Plates 16 to 25; 1 Map) CRAwrForD NiiGATEs <7 iGer" otis Bee aia ote ee ey an ee nee a eT INKS) CZINDINIS) co 9 0 0 Baga wo kG See gaat Vora. of os. he IGA Notes on the Collection of Tritonia festiva iin 1873) from the Seas of Japan (Gastropoda : Nudibranchia) (1 Text figure)
KIkuTARO BABA Range Extension of Tochuina tetraquetra (PaLias, 1788) to Hokkaido,
North Japan (Gastropoda : Nudibranchia). KrxuTarO BABA Current Paleontologic Investigations on Cenozoic Marine Mollusks of the West Coast of North America. WarreN O. AppICoTT & SABURO KaNNO METHODS & TECHNIQUES... . aon ss(/1P) A Simplified Vacuum Apparatus for Collectine Ae Nae (1 Text figure) J. SHERMAN BLEAKNEY
Technique for Extraction and Mounting of Gastropod Radulae. GrorcE E. RaDWIN
Note: The various taxa above species are indicated by the use of different type styles as shown by the following examples, and by increasing indentation.
ORDER, Suborder, DIVISION, Subdivision, SECTION,
SUPERFAMILY, Famity, Subfamily, Genus, (Subgenus) New Taxa
Vol. 12; No. 1
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Division Of Molluske sctionall Library
Page |
Anatomical Notes on the Mactrid Bivalve,
Raeta plicatella LAMaRcK, 1818,
with
A Review of the Genus Raeta and Related Genera
HAROLD W. HARRY
Texas A&M Marine Laboratory, Galveston, Texas 77550 and Rice University, Houston, Texas 77001
(20 Text figures)
TABLE OF CONTENTS
Mina itech Ur Cte TD es secsesccesces ase ast ieeas vas saasteevsesdvasseesveatsvsesvsssesectontieosestee? I
Part I. Raeta plicatella a. Ecology Ip e hia Vl on terete a setacceemterttortnrstntoneccommtionmneste ize 2 c. Anatomy d. Anatomical Discussion
Part II. Systematics a. Genus Anatina b. Genus Raeia s. s. c. Subgenus Raetina __....... d. Subgenus Raetella _...... e. Systematic Discussion
Weiteratune Cited) ee ee ede ans QI
INTRODUCTION
SEVENTY YEARS AGO, DALL (1898, p. 907) wrote of this
species: “Notwithstanding the fact that dead valves of this shell are found in windrows on the beaches at some points of the south- ern coast, the character of the soft parts is unknown, and I shall be very greatly obliged to any one who can furnish me with a specimen of the animal in spirits in order that its systematic position may be positively settled.”
Apparently nothing has yet been reported on its ana- tomy. It may, therefore, be worth recording notes which I made on a single intact live specimen, and fragments of two others, for this species has several unusual structural
characters which heighten interest about its enigmatic ecology and systematic relationships.
Raeta plicatella is the type of its genus. I have therefore included a review of this genus and related ones. Since nothing is known of the anatomies of any of the species of the other genera, conclusions on the systematics of this group must be based on characters of the shell. Descrip- tion of the shell of R. plicatella is deferred to the system- atic part of the paper.
I am indebted to Mr. Pat Burke, Mr. Donald Harper, and Mr. Ronald Tomas for assistance in field work, and to the staff of the Mollusk Department of the United States National Museum for their generous hospitality while I studied the National Collection.
PART I. Raeta plicatella (Lamarck, 1818) Ecology:
Single, fresh valves are often abundant on the beaches along the Gulf of Mexico in Louisiana and Texas. Very rarely shells have a bored hole, probably made by Poli- nices duplicata Say, 1822. Joined valves of Raeta plica- tella are rare and live specimens even more so. I have found only two shells containing the flesh on the beach. Both were at the edge of the surf, and both had been picked open on the central part of the disk by sea gulls. Birds may account for the dearth of live specimens, even in the winter when rough surf often tosses up live snails and bivalves whose shells afford them more protection
Page 2
(Anadara, Noctia, Dosinia, Tellina alternata Say, 1822, Busycon, Polinices and others).
Raeta plicatella seems to be a species of the outer part of the surf zone, a region difficult to sample. The mollusks which live there are chiefly known by being cast up on the beach by rough surf, for they are not regularly found in the inner part of the surf zone frequented by swimmers, and several of them are not taken by dredging in waters seaward of this zone. At Galveston, the outer surf zone is only a few hundred yards wide, and from 2 to 3 fathoms depth. It is so close to shore that boats large enough for trawling and dredging cannot often be used there. In more than 60 dredged samples from 3 to 18 fathoms off Galveston, single, small juveniles of R. plica- tella occurred in two samples at 3 fathoms, and single fragments of larger shells were found in two samples of 5 fathoms. Not even identifiable pieces of shell occurred in any of the others.
I had never seen shell fragments or juveniles of this species in the Galveston Bay complex, until the single intact specimen was found which furnished most of the anatomical data of this report. It was dredged from 2 fathoms, 14 October 1967, at the east end of the intra- coastal canal cutting Pelican Island, Lower Galveston Bay.
Occasional live specimens of mollusks living in the outer surf zone are found in Galveston Bay. These are usually juveniles, or rarely small adults. Their scarcity and size suggest that their larvae have invaded this area, which is adjacent and connected by water to that in which they normally live, but that they are not able to complete their life cycle and establish perpetuating populations in the bays. Examples of such adventitious species found in the more saline parts of the bays, but with established populations only along the Gulf shore are Dosinia discus Reeve, 1850, Tellina alternata Say, 1822, Anadara brasili- ana, Periploma inequalis C.B.Apams, 1842, Noetia ponderosa Say, 1822, Pitar texasiana Dati, 1889, and Donax variabilis Say, 1822.
Behavior:
In the laboratory, the live specimen was lethargic. It did not move about in a dish of seawater, and the foot was not seen extended beyond the shell. The shell gaped slightly and continuously during the several days of ob- servation. The siphons were not withdrawn, even when the specimen was handled.
Several colonies of the stalked ciliate protozoan, Car- chestum, were attached to the siphons near their tips, and also found on the periostracum between the margins of the valves along the postdorsal slope of the shell. A small colony of an encrusting bryozoan was on the
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periostracum of the fused mantle margin near the pedal opening. The surface of the shell was clean and had no extraneous organisms. The presence of Carchesium and the bryozoan suggest this animal did not burrow, but was on its side on the substrate. This inference is further supported by the nature of the foot (see below).
External Anatomy:
The siphons (slightly contracted in Figure 1) are about 2 as long as the shell, and joined throughout their length. There is a slight groove between the two, on the sides.
Figure i
Diagram of the external anatomy of Raeta plicatella from a live, partly retracted specimen. The left valve and mantle have been removed. aa -—anterior adductor muscle _ap — anterior pedal retractor muscle f — foot g—gill Ip — labial palp pa-— posterior adductor po — pedal opening in mantle margin __ pr — posterior pedal retractor r—rectum sm-—siphonal membrane sp -—siphonal pocket wl-—right wall lamella of waste canal v— ventricle of heart
The diameter of the excurrent siphon is about 4 that of the incurrent one. The opening of the excurrent siphon has a thin, transparent, conical flange extending from it, with a small opening at its tip. There are no papillae around the excurrent siphonal tip. The incurrent opening has no valve flange, but numerous short papillae are along its margin. Two papillae of this series, between the two siphonal openings, are larger than the rest. Every 10 minutes or so the siphons contracted rapidly, but only for a short distance, and the feces were expelled through the excurrent opening.
A white, wavy seam on the top and bottom of the siphons evidently represents the junction of the two sides of the periostracum. This cuticular sheet extends to the
Vol. 12; No. 1
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tips of the siphons, lines the siphonal retraction cavity of the mantle, and all of the exposed mantle margin. It is very thin, and scarcely evident over the outer shell surface.
The color of the living tissue was varied. There was no gross evidence of hemoglobin, the blood being colorless and the nerve ganglia white. The ovary was white, the liver the usual olive brown, the kidney was faint purplish brown. The labial palps and gills were faint orange yellow, and the foot was dingy white. The rest of the flesh was without notable color.
The mantle is very thin, and colorless over the disk of the shell. The disk part is attached in small round spots, which are not the origin of muscle cells, but seem to be epithelial. The spots of attachment are 1 to 2mm in diameter, and widely scattered.
The kidney extends into the lobes of the mantle, ex- tending downward well below the free margin of the gills (dashed line, Figure 2). This part of the mantle is thickened.
The margins of the mantle lobes are fused to each other along the dorsal, anterior and ventral margins of the shell, and the attachment is thick and muscular. At the antero-ventral margin there is a small opening in the
x Oy
as
SC pb
Figure 2
Visceral mass and structures in the mantle at the hind end of the body.
ap — anterior pedal retractor muscle ec — excurrent chamber of mantle cavity i-intestine hp-liver k-—kidney pb — posterior end of gills
pg—pedal ganglion = pr—posterior pedal retractor muscle
rms-— retractor muscles of siphons _ sc — style sac s—septum separating mantle chambers sm -—siphonal membrane sO—sense organ ssg — suspensory septum of gills st — stomach v-—ventricle of heart vg -— visceral ganglion
cg — cerebral ganglion ga—gill axis ov — ovary
marginal fusion, the pedal opening (Figure 1). This is surrounded on its inner margin by a thin, narrow velum, which may represent the inner mantle margin lamella. The latter is not evident as a distinct entity elsewhere. No “fourth pallial aperture”, below the siphonal pocket, was evident (see YoncE, 1948). At the hind angle of the shell, there is a large opening into the deep, blind siphonal pocket (Figure 1). |
In front of the siphonal pocket, the siphonal retractor muscles form a flat, triangular mass in each mantle lobe, with the apex pointing forward. These muscles are small bundles, not forming a continuous sheet, but with spaces between them about half as wide as each bundle (Figure 2, rms). The origin of the siphonal retractor muscles is along the pallial sinus scar of the shell. They converge toward and extend into the siphons as longitudinal re- tractors.
A thin, transparent diaphragm of mantle epithelium extends forward horizontally from between the inner openings of the siphons. This septum is a continuation of the diaphragm formed by the gill attachments, and with the latter it completely separates the incurrent and excur- rent chambers of the mantle cavity (Figure 2, s).
There is a single lamella of mantle extending along both sides and the top of the incurrent siphonal opening, but not across its bottom (Figure 2, sm). This is the siphonal membrane (Kettoce, 1915). A pair of lamellae of moderate width extend forward from the ends of the siphonal membrane, one attached to each mantle lobe, to a point below the apex of the pallial sinus scar (Fig- ure 1, wl). These are the wall lamellae of the waste canal (KELLOocG, op. cit.). These three lamellae have intrinsic musculature, which on contraction decreases the height of the lamellae. They probably serve to guide pseudofeces into the incurrent siphon.
The fused edge of the two mantle lobes ventrally is very thick (Figure 3), and filled chiefly with mantle margin muscles. Some of these pass from the position of the pallial line to the free, or exposed mantle margin, and thus pull the mantle margin upwards, away from the mar- gin of the shell. But the bulk of the muscles pass trans- versely, forming a mantle margin adductor muscle in this area, as in certain pholads, such as Cyrtopleura costata. There are a few strands of longitudinal muscles in this fused mass, particularly on the upper surface.
The periostracum covering the free, ventral surface of the fused mantle margin has a white streak medially. Just above this streak are the two minute grooves (Figure 3, pg) in which the periostracum is formed, between what is homologous to the outer and middle mantle margin la- mellae of other bivalves, which do not have fused mantle lobes in this region.
Page 4
The anterior adductor muscle (Figure 1, aa) is very elongate and narrow, extending along the anterior curve of the shell from the front end of the pedal opening to the front end of the hinge plate. It is merely a broadening of the mantle margin adductor muscle, and not a separate entity. The hind adductor muscle is reniform, and small for the size of the shell. Both muscles were opaque and white, with no gross evidence of “quick” and “catch” parts differentiated.
WC wl
Figure 3 Diagram of transverse section of ventral margin of Raeta plicatella, about one fourth the length from the hind end.
m— mantle lobe rm — retractor muscle of mantle margin tm — transverse muscle of mantle margin
wl — wall lamella
Im — longitudinal muscle of mantle margin peg — periostracal groove sh — shell
wc — waste canal
The foot is atrophied to a small, elongated, wrinkled mass, flattened laterally and rounded at the free end. The free margin is acutely keeled, but without any groove. Probably the foot is never extended beyond the shell mar- gin in specimens of this size (44mm long). It is some- what muscular, the circular muscles extending only a little way up on the front margin of the visceral mass, but not up the hind margin of it. Anterior and posterior pedal retractor muscles each form a thin bundle along the front and hind margin, respectively, of the visceral mass (Figure 2, ap,pr). At their top, each muscle divides, the front one originating on the shell valves on each side and slightly above the mouth, and thus just above the anterior adductor muscle.. The hind pedal retractor has the rectum passing between its two short branches.
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It originates on the shell valves just above the posterior adductor muscle scars.
The visceral mass has an exceptionally thin wall, with little musculature. Probably this is a consequence of the atrophied foot. The covering is so thin that the internal organs of the visceral mass are easily seen through it.
The gills have two demibranchs on each side. The ascending lamellae of all four demibranchs are attached to the mantle at about the level of the gill axes. The gill axes form almost a straight line running obliquely from a point a little way in front of the siphonal inner openings, forward and upward to a point just below and slightly in front of the umbos of the shell. The anterior halves of the attachment of the two gills are separated by the visceral mass, but behind it they are so joined that the excurrent chamber of the mantle cavity is completely separated from the incurrent one. Behind the visceral mass, the ascending lamellae of the medial demibranchs are attached to each other along their upper margins. The gill axes are here each suspended by a thin vertical septum, so that the excurrent chamber is divided into three compartments, two lateral and a medial, between the hind margin of the visceral mass and the lower end of the hind adductor muscle (Figure 2, ssg). Behind that point there is only a single tubular excurrent cham- ber, limited below by the horizontal septum of the mantle, laterally by the mantle proper, above by the lower surface of the kidney and the posterior adductor muscle, and behind the latter, an additional short horizontal septum of the mantle.
The outer demibranchs are not as wide as the inner, and do not extend as far forward. They are semilunar in shape, with short filaments at both ends, increasing grad- ually and regularly in length to the middle of the demi- branch. The medial demibranchs extend a considerable distance forward, and actually begin well in front of the hind end of the attachment of the labial palps. The gills are eulamellibranchian, pleated, and all demibranchs have a groove along their free margin.
The labial palps are large, subtriangular, with convex anterior margin, concave posterior margins, and rounded ventral angle (Figure 1). They are attached along a straight line to the visceral mass by their dorsal margin. The two free sides of this triangle have a narrow strip lacking the numerous vertical ridges which cover the opposing surfaces of the labial palps. These ridges extend almost to the mouth; the medial parts of the palps are narrow, with simple free margins.
Only a few major features of the internal anatomy could be worked out. The two liver lobes, right and left, are rather small, and fill the periphery of the upper, ante- rior part of the visceral mass. The gonad, an ovary in the
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one complete specimen available, fills the posterior half of the visceral mass peripherally, pushing dorsally over the stomach and under the pericardium. The antero- ventral part of the visceral mass has a large coiled mass of intestine (Figure 2).
The esophagus is short, opening into a large oval stomach. The interior of the stomach is much complicated with ridges and folds, details of which were not worked out. Most of the interior was covered by a loose lining of cuticular material, the gastric shield. A sorting area, of several oblique ridges on the left side, was not covered by the shield.
Each liver lobe consists of a thin-walled, branched tube. The liver follicles, glandular in appearance, are not branched, but clustered about the tips of the smallest
branches of the hepatic ducts. Each follicle is about
0.1 mm in diameter.
Postero-ventrally, the stomach receives the style sac on the left, and the slightly smaller intestine opens beside it on the right. The style sac and intestine are completely separated, the former plunging down to the tip of the visceral mass and turning forward for a short distance, ending blindly. A well-formed crystalline style was pres- ent, after the clam had spent several days alive in the laboratory, and even after it had been opened for 2 days, maintained in the refrigerator at 4° C in sea water.
The intestine is thin-walled, light brown, and evidently without musculature. A dark brown fecal rope was passed along by ciliary activity. The intestine is unusually long, about several times the length of the shell. It is mostly coiled in the lower front part of the visceral mass, in a part of the hemocoel free from liver and gonad. Two parts of the intestine are recognizable on the basis of size, position and internal structure. The first part (duo- denum) is imbedded in the ovary on the right of the style sac, and passes forward near the lower end of the visceral mass; it also forms the first few coils. It is about twice the diameter of the second part, the jejuno-ileal intestine. The latter makes up most of the coils, three of which loop symmetrically from side to side peripheral to the lower end of the liver; it then passes into the ovarian mass well ventrally, turns upward behind the style sac and enters the front end of the pericardium, beyond which point it may be called the rectum. After leaving the latter it passes between the two kidney lobes, over the outer sur- face of the posterior adductor muscle and opens into the hind part of the suprabranchial chamber of the mantle cavity, just in front of the excurrent siphon.
I could not determine the relative lengths of the large and small intestine, nor their junction. Perhaps it is a gradual transition. The large (duodenal) intestine has a huge lamella, or typhlosole, in it, much thicker than the
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intestinal wall. At intervals of a few millimeters, this has short branches at right angles, but only along one side. These resemble buttresses. I could find no typhlosole in the small intestine, but perhaps one is present as a mere strip of cilia.
Feces:
The pseudofeces, consisting of particulate material as- sembled in the incurrent mantle cavity and rejected through the incurrent siphon, are poorly consoltdated ropes of sediment, slightly larger than a millimeter in diameter and a few centimeters long.
True feces are of two types, which may be called ropes and pellets (Figure 4). The pellet type was seen in the
Figure 4
Feces. Rope type on right, an unopened pellet left above, and a pellet cut transversely on left, below.
rectum of the damaged specimens from the beach, and the rope type in the intestine of the intact specimen found in the bay. This specimen voided both types in the laboratory, and from that material Figure 4 was drawn. The rope type of feces evidently passes through the intestine with little rearranging of the materials involved. It consists of a single strand, 80 to 100mm long, with seg- ments of dark tan material alternating with segments of dark olive color. The lengths of the two segment types are not constant. Probably the olive colored material is derived from the liver, and the tan material is of undi- gested particles which entered the mouth. These were not
Page 6
studied in detail. The packaged configuration of the rope, bent back upon itself several times as shown in Figure 4, probably occurs as the rope is defecated into the supra- branchial mantle chamber. This package has been passed from the animal, as had numerous pellets.
The pellet feces were probably in the specimen when captured. They are constant in diameter, about 0.69 mm, and slightly variable in length, about 0.96 to 1.23mm long, with longer pellets being more abundant. Each pellet is elaborately constructed. The pellets are smooth, regular cylinders with abruptly truncated ends, one being slightly convex, the other slightly concave. The surface is uni- formly light tan colored, evidently of fine particles held compactly together with mucus. There is a single line, slightly incised, which begins in the middle of one end, makes about one complete turn on the lateral surface, and ends at the middle of the other end of the pellet.
Breaking a pellet open gently reveals a central cavity which seems not to extend quite to the ends. Its diameter is about 4 that of the pellet, and.it is reniform in cross section. This cavity is loosely filled with granules of vary- ing sizes, all larger than those of the outer part. The outer part of the pellet has about five layers, probably of only one continuous sheet, wrapped around the central cavity. The innermost layer is wider and less firmly con- solidated than the others. The layers bend toward the concave side of the central cavity, and the spiral line on the outside seems to correspond to this also.
At higher magnification, the particles of the outer shell of the pellet all seem to be inorganic, angular granules, rarely as large as 3u. No Brownian movement could be seen in a squash preparation in sea water, possibly be- cause the mucous matrix was too viscous. The granules of the central cavity are irregular spheres, from 10 to 14u in diameter. These are hyaline, golden brown and bright in reflected light. Also present were a few glassy angular flakes, colorless and polygonal, with sharp edges and angles. These are about 0.30 mm in maximum dimension. I was unable to find any organismal remains in the pellets, such as diatoms, even at 970 * magnification.
The pericardium is a large, spacious, cuboidal sac located below the umbos (Figure 2). The ventricle of the heart surrounds the rectum, which transverses the peri- cardium lengthwise dorsally. The ventricle has two small projections antero-dorsally. The auricles are thin-walled triangular sacs diverted ventro-laterally. They nowhere touch each other. A light brown color on their exterior surface suggests a pericardial gland is present, but it does not extend onto the pericardial wall. There are two minute reno-pericardial openings on the post-ventral sur- face of the pericardial sac.
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The kidney consists of two huge sacs, between the pericardium and the posterior adductor muscle. The pos- terior pedal retractor muscle passes between these sacs. Each sac is elongate, but bent upon itself, so that there is a dorsal moiety, beginning near the pericardium and passing backward to the adductor muscle, then turning forward ventrally to form the ventral moiety, which ends again at the pericardium. The large extensions of the kidneys into the mantle are projections from the upper moiety of each sac. The reno-pericardial passage is at the front end of the lower moiety of each sac, and a little farther back each lower moiety has a renopore opening into the excurrent mantle chamber, just in front of the post-pedal retractor muscle. The interiors of the kidney sacs are spacious; there are no trabeculae, but a smooth wall with large cilia, and numerous small holes opening into it (Figure 5). These are the ends of short narrow
Figure 5
On the left, a part of the wall of the kidney, showing follicles
extending from its outer surface and pores by which they open on
the inside. Cells are shown in only one follicle. On the right, a single kidney cell from inside a kidney follicle.
ducts of the kidney follicles. Each follicle is branched two or three times; they are thin-walled, transparent sacs (about 0.3mm diameter whose cavities are almost oc- cluded by the bulbous ends of the excretory cells. These cells are part of the follicular wall, but they extend in- ward by narrow, short stalks. The free end of each cell is spherical, having a large vacuole which holds a light golden fluid. The fluid does not seem to mix with sea water. Each vacuole also has a spherical mass of golden brown, opaque granules.
The members of all three pairs of ganglia of the nervous system are fused, so that there are no commissures (Figure 2). The connectives between ganglionic pairs were not traced. The cerebral ganglia are just above the mouth. They are intermediate in size between the other
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two pairs. The pedal ganglia are 0.19mm long, and located at the front end of the base of the foot. The visceral ganglia are 0.3 mm long, and on the roof of the excurrent mantle chamber below the kidneys, but well in front of the posterior adductor muscle.
There are two prominent sense organs on the mantle, one on each side of the upper part of the inner end of the incurrent siphon, just in front of the median accessory mantle fold. These may be osphradia. Each is connected by a large nerve to the visceral ganglion on its side. They are elongate oval masses, about 0.1 mm wide and 0.3 mm long, and as high as they are wide.
The ovary of the intact specimen was a large, dendriti- cally branched multifolliculate organ, the follicles being slightly less than 0.1 mm diameter, containing thousands
Figure 6
Tape worm larva from: cyst on intestine. Terminal sucker everted in complete specimen, retracted in the smaller figure.
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of eggs which appeared to be about ripe. The eggs are white, about 44, diameter, with a large germinal vesicle 27. diameter containing a nucleolus 13 diameter. There seems to be a single gonopore, opening into the front of the pericardial cavity just to the left of the rectum. If so, the eggs evidently must pass through the pericardium and kidney to reach the exterior.
Parasite:
A small cyst containing tapeworm larvae was attached to the outer surface of the intestine just below the stom- ach. It was white, and at first mistaken for a piece of the ovary. The cyst was thin-walled, elongate, with an irregu- lar surface. It contained several dozen larvae, each coiled to form a sphere. Released from the cyst into sea water, the larvae squirmed with peristaltic movement and everted the terminal sucker. They attached with the lateral suckers (bothridia) and moved along a glass surface by alternately attaching and releasing them.
The larva (Figure 6) is fusiform, about 54y long. It is colorless, and the body is filled with small hyaline granules. The hind end tapers acutely, and the front end is rounded, with a deep, cup-shaped, muscular terminal sucker. This can be extended forward, or withdrawn to the level of the bothrydia. There are four elongate oval bothrydia, with small bases, attached symmetrically around the scolex. The cavity of each bothrydium is divided by two transverse partitions into three chambers (areolae) of equal size. No spines were seen at 100 x magnification, nor could any internal anatomical details be made out.
Anatomical Discussion:
Most notable features of the anatomy of Raeta plica- tella are the extension of the kidney into the mantle, the thin wall of the visceral mass, the atrophied foot, and the enormously long intestine. The abnormal ecological occurrence of the specimen on which most of this ana- tomical account is based might cast doubt upon some of the data on habits and anatomy. There is indeed an in- trinsic conflict between the two: the long siphons and atrophied foot suggest this is a deep burrower which does not move about much in later life. An atrophied foot in late life of bivalves is probably more common than real- ized. Among species of the Galveston area I have seen such in Periploma orbicularis Guppy, 1878 and Diplo- thyra smithit Tryon, 1862, neither closely related to each other nor to the Mactridae. But of the anatomical char- acters, I suspect only the small size of this specimen is abnormal in terms of other features; its presence above the substrate, as suggested by the epizoa growing on it, may indeed be unusual.
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The diversity in soft anatomy of the Mactridae ap- pears to be larger than it is within most families of bivalves. I will not here try to summarize all of the liter- ature on this subject, which, though extensive and scat- tered, constitutes a mere beginning in comparison to the number of species whose anatomies are unknown. A well- developed foot is present in all species previously studied, and the atrophied foot of Raeta plicatella is unique. Fu- sion of the mantle margin behind the pedal opening varies. In some species, the mantle lobes are completely free between the anterior adductor and the siphonal pock- et. In others, the lobes are extensively held together along the posterior half of their margins by a fusion of a cuticular extension of the periostracum (Lutraria, fide Yonce, 1948). Dati (1898a) found free mantle lobes with papillae in Resania, but in Zenatia he says they are fused along their hind half, although he does not say whether the fusion is cuticular or represents cellular con- tinuity. In Raeta the fusion is definitely cellular, and this genus therefore represents a third condition of the mantle margin.
A “fourth pallial opening” which is a small hole be- tween the mantle edges just below the siphonal pocket, is present in some Mactridae and other families, according to Ke.ioce (1915) and Yonce (1948), but such an open- ing is absent in Raeta.
The wall lamellae of the waste canal, as these structures were termed by Kettoce (1915), have been given only passing attention in the literature except by that author and YoncE (1948), who termed them “mantle folds”. Dati (1898a) described similar folds in the New Zealand genera Resania and Zenatia, but called them “sensory lamellae”.
The siphonal lamellae and wall lamellae of the waste canal may be structures limited to the Mactridae, al- though YoncE says that folds similar to the wall lamellae, but probably differing in function, occur in the Tellina- cean genera Scrobicularia, Abra and Macoma. A siphonal lamella forms a complete ring in the venerid Saxidomus as described and figured by Kettoce, but whether this is homologous to the semicircular lamella of the incurrent siphon of the mactrids is unknown. Among mactrids, the siphonal lamella is said to be absent in Lutraria (YonceE, 1948), and both that and the wall lamellae are absent in Spisula planulata Conrad, 1837, according to KELLOGG.
Whether or not gills are pleated or smooth, without vertical folds seems to be a character which varies at the generic or specific level. RmEWoop (1903, pp. 237 ff.) found flat, homorhabdic (i.e., not-pleated) gills in four species of Mactridae on which he reported. Whether the pleated gills of Raeta plicatella have heterorhabdic fila-
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ments at the grooves between the pleats was not deter- mined.
The persistence of a crystalline style in bivalves which are not feeding, or at least while they are in the labora- tory for some time with minimal food, is a phenomenon which seems to be characteristic of most marine ones I have studied. This contrast with the oysters and unionids, which seem to resorb the style quickly when not feeding, and reform it in the- presence of food.
The opening of the gonad into the pericardium, so that the gametes transverse the kidney lumen and emerge through the renopore is a point which bears checking in further studies. PELSENEER (1911, p. 100) thinks such a condition is primitive, and limited to some protobranchs, Anomiidae and Pectinidae. From his reservations on the matter, it is evident that the gonopore is difficult to detect in bivalves.
Athough Moore (1931) called attention to the varied form of fecal pellets in marine mollusks, and suggested that careful study might yield valuable data on phylo- geny and food habits, nothing further seems to have been published on the subject. Moore did not describe the pellets of any mactrid bivalves. The feces of Raeta plicatella are markedly different from any he described in Pectinidae, Mytilidae, Tellinidae and Semelidae. The elab- orate pellets of R. plicatella are very similar to those of the pholad C'yrtopleura costata LinNAEUs, 1758, but differ in minor details (unpublished data).
The presence of an osphradium in bivalves, homologous to that of snails, is a moot point. Only occasionally have such structures described above as an osphradium been noted. PELSENEER (1911, p. 112) calls these “sensory organ of the inhalent siphon”, and cites them in the Mactridae.
The parasite found is evidently a larval tapeworm of the order Tetraphyllidea, the adults of which live in the intestine of elasmobranch fishes. Larvae of this type are called “Scolex pleuronectes Mit ver, 1788” or “Scolex polymorphus Rupotput, 1819”, binomials which do not have exact taxonomic significance. As Suip.ey (in SoutH- WELL, 1925, pp. ix-x) points out, “It is extremely diffi- cult to identify the larval form of a cestode with its parents. It is a wise tapeworm that knows its own father”. Apparently, the structures of the scolex in these larvae may vary considerably at different stages (ages) (SouTH- WELL, 1925, pp. 138 - 140). The one found in this study might be assigned to the family Phyllobothriidae, in lacking hooks on the scolex, yet the general form of the bothrydia is more like that of the other family in this order, Onchobothriidae, which, however, has no hooks in the scolex. Although most of these larval tetraphyl- lideans have been found in teleost fish, Hyman (1951, p.
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354) notes that they have been found in invertebrates of several groups, including mollusks, and she figures one (J. c., figure 131 D) from the foot of a clam.
Part II. SYSTEMATICS
Review of Raeta and Related Genera:
Anatina ScHUMACHER, 1817
Raeta Gray, 1853 has sometimes been considered a dis- tinct genus, a position adopted here. Other writers have considered it indistinguishable from, or only a subgenus of, Anatina SCHUMACHER, 1817, or its junior synonym, Labi- osa Miter, 1832. The nomenclatural problem of Anatina versus Labiosa has been recently explored by KEEN (1961, q. v. for relevant bibliography), who gave good reasons for accepting the name Anatina as valid in the Mactridae. Moreover, she has shown that the type species of Anatina SCHUMACHER, 1817 is a western Atlantic species, Mactra anatina SPENGLER, 1802. This has been cited in much of the literature as Anatina or Labiosa lineata Say, 1822, but is now correctly identified as Anatina anatina (SPENG- LER, 1802).
Despite KEEN’s study, the problem of whether to ac- cept Anatina SCHUMACHER or Labiosa MULLER has not been put to rest. OLsson (1961, p. 332) accepts Labiosa, as does Vokes (1967, p. 274), both apparently on the assumption that a use of the generic name Anatina by Bosc in 1816 is a validly proposed name, also a junior synonym of Laternula “BotTEN” Ropine, 1798. The latter is a relative of the anomalodesmacean genus Peri- ploma. According to that line of reasoning, Anatina would therefore not be available to use in the Mactridae. The point of contention seems to revolve on what Bosc (1816, p. 492) said in defining Anatina; his description is here quoted:
“ANATINE, Anatina. Genre de coquilles bivalves établi par Lamarck aux dépens des Solens, sous la consideration d’une petite lame saillante 4 chaque valve en dedans ow s’attache le ligament.
“Le Solen canard sert de type 4 ce genre, que est fort voisin des corbules et des Rupicoles. (B)”.
If we consider, as Keen has correctly done, the type cited by Bosc to be vernacular and therefore invalid, one might still argue that this is a genus validly described but without species. Whereas it may be entirely possible to conceive of a genus without species in the realm of pure thought, as may be done in modern logic, such a concept is absurd when applied to real biological entities.
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Anatina anatina is a relatively rare shell on the beaches from New Jersey to Brazil. At Galveston it has not been found in the bays, but only as shells on the sandy beach and in a few dredged samples off shore. Apparently it does not occur in the Antilles.
The differences between the shell of Anatina anatina and the species from the West Coast of the Americas have been discussed by Keen (1961), who pointed out that the West Coast species should be called Anatina cyprinus Woop, 1828. I could find only a single valve of the latter species in the National Collection. It is from Topolobampo, Sinaloa, Mexico. Otsson (1961) has given a descrip- tion and further distribution records of this species under the name Anatina anatina. As far as I can determine, the two species from the coasts of the Americas are the only ones which should be put in the genus Anatina ScHuUMA- CHER.
The synonymy of the genus Anatina and the two spe- cies included in it will not be repeated here, since KEEN (1961) has provided a meticulous account of these earlier in this journal, and I have nothing to add. The anatomies of the soft parts of these species is unknown, but it is worth pointing out that many recent authors (e. g., YONGE, 1948) refer to the anatomy of the “‘Anatinacea” when they are referring to the anatomy of the Anomalodesma- cea of modern classification, i.e., the Periplomatidae, Lyonsiidae, Pandoridae and related groups. This confusion results from the fact that PELSENEER (1911 and earlier works), who paid scant attention to nomenclature, used the term Anatinacea based on Anatina as a genus in Periplomatidae. PELSENEER wrote most of what is known on the structure of the bizarre Anomalodesmacea, and most recent anatomists have unfortunately accepted his competency in nomenclature no less than in anatomy.
The shell of the type species of Anatina SCHUMACHER has been studied in more detail than has been previously reported, and a description of it will be useful for com- parison with Raeta and related genera.
Anatina anatina (SPENGLER, 1802) (Figures 7 to 10)
Shell very thin, fragile, white, translucent, elongate ovoid, the front end somewhat more sharply rounded than the hind. Size moderate (65 mm long, 43 mm high, 28 mm wide). Equivalve, and slightly inequilateral, the umbos being just behind the midpoint of the length. Umbos touching, minute and distinctly prosogyrous. The hind end of the shell gapes. The umbonal fourth of the shell has faint concentric corrugations, parallel with the growth striae, forming ridges and grooves on the inner surface.
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The lower three fourths of the shell is smooth. A lunule is poorly defined by a shallow sulcus extending from the umbos in a broad arch about half the length of the
Figure 7 Anatina anatina, dorsal view. Galveston, Texas, length 43 mm.
antero-dorsal margin. This becomes wider toward its ante- rior end. On the medial side of the lunular sulcus is an opaque line not structurally differentiated on the outer surface. This is the line of attachment of the anterior hinge plate. The post-dorsal margin is about two-thirds as long as the antero-dorsal one. It is strongly turned later- ally, enhancing the posterior gape of the shell. A low rib, scarcely higher than wide, extends from the umbo to the post-ventral part of the shell: this may be a corcelet la- mella. In front of the rib, and separated from it by a space about half as wide as the space behind the rib, is a line defining an abrupt change in shell texture. This may be called the periostracal line. Along a narrow but poorly defined strip in front of the periostracal line vermiculate sculpture is evident. This is made up of minute wrinkles in the shell surface, joining and branching and mostly
Figure 8
Anatina anatina. Galveston, Texas, length 33 mm
directed radially. They are not present over the smooth part of the disk in larger shells, but are uniformly distrib- uted, although very faint, on all the adumbonal corru- gated region. In fresh shells, the surface of the thin, persistent, faint tan periostracum is silky in reflected light. But behind the periostracal line, the periostracum is lusterless, and less persistent. There are only coarse growth lines in the shell behind the line, and a moderately thick layer of opaque chalky material is deposited there between the periostracum and ostracum,
The disk of the shell is distinctly swollen along a line from the umbo toward the antero-ventral angle. This gives the umbos the appearance of being directed back- ward, whereas in reality they are turned forward at their
tips.
Figure 9 Interior of same valve as shown in Figure 8.
The pallial line is narrow, located close to the ventral edge of the valve, with slightly irregular dorsal margin. The anterior adductor scar is tear shaped, located direct- ly on the pallial line; it has a pallial line extending dorsal- ly from it to the front end of the hinge plate. Just above the anterior adductor scar the dorsal pallial line has a slight swelling, probably representing the anterior pedal retractor scar. The pallial sinus is large, rounded in front. It extends forward to a point below the umbos. Its lower side is well above the pallial line, not confluent with it. The posterior adductor scar is subtriangular, and the posterior pedal retractor scar constitutes a small con- stricted area confluent with the adductor at the dorsal tip of the latter. The corcelet ridge is evident internally as a shallow groove.
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The hinge plate is slightly thicker than the valve. The front and hind halves extend along the front and hind dorsal margins for about half the length of the latter. The front half of the hinge plate is thus slightly longer than the other; this part of the hinge plate is strongly oblique to the valve surface, so that there is a deep space between the two. Its free margin is deeply excavated in a gentle curve, so that the trough between the hinge plate and valve is minimized. The hind half of the hinge plate is almost flat and horizontal, with its free margin almost straight. The resilifer is a triangular pit below the umbo, with its lower margin projecting as a rounded curve below the hinge plate.
Figure 10
Anatina anatina. Hinge of shell. Upper is right valve. The valves are of different shells.
In the left valve, the cardinal tooth is moderately thick, and the sinus between the arms is large and deep. The sides of both arms are flat. The hind arm is about half as long as the front one. It projects over the resilifer as a free point. There is a thin antero-lateral lamella separating the front arm of the cardinal from the front hinge plate. A similar low, thin lamella is a little way behind the resilifer pit, separating it from the hind hinge plate. These two lamellae reach to the free margin of the plate, forming large oblique angles.
The attachment of the tensiliar ligament is a semi- lunar depression on the shell margin, beginning at and extending behind the umbo. This depression extends over the tip of the resilifer pit, concealing it. The front half of the curved (ventral) margin of the ligament pit is turned medially, and to its lower (front) surface is fused a small lamella projecting as a minute spine over the resilifer pit. This “spur” lamella is parallel to the hind ramus of the cardinal, separated from it by a deep groove which receives the hind cardinal ramus of the right valve.
In the right hinge the resilifer and ligamental shelf are much the same as in the left. There is also a single posterior lamella a little way behind the resilifer, separ- ating it from the shallow trough of the hind hinge plate. The cardinal and antero-lateral lamellae are different from those of the left hinge. The cardinal is chevron shaped, with the posterior arm straight and about half as long as the anterior arm; the dorsal surface of the hind arm is fused to the medially turned edge of the ligamental plate, and the lower end of this arm extends free over the cavity of the resilifer; the medial (free) margins of the two arms have a deep excavation where they meet at the apex of the chevron. The anterior arm is sharply curved in its upper half, by being bent forward. This part is fused with the umbonal part of the antero- lateral lamella, which projects free from the lower part of the front arm of the cardinal, as a minute but thick and consistent structure.
The lateral lamellae of this species are probably homo- logous to the lateral teeth of other heterodonts, and indeed of other mactrids such as Spisula and Mactra. But in Anatina and Raeta they are more like cardinal teeth, radiating from the umbo, but not paralleling either the shell margin or the margin of the hinge plate; there is moreover only a single front and hind lateral lamella in both the right and left valves, whereas in Mactra, Spisula and some other genera, there is a single one before and behind in the left valve which fit between a pair at each place in the right valve. Also, in the latter genera, the laterals are parallel to the shell margin and, of course, to the margin of the hinge plate. The oblique, single lateral lamellae of Anatina and Raeta remind one of the laterals of the Cardiidae, which curve out as low ridges in a radiating arc from the umbo, on the inner surface of the shell.
Whatever the soft anatomy of Anatina may disclose, the characters of its shell seem sufficiently diverse from Raeta to separate the two generically; the presence of the periostracal line and the lateral flexing of the post- dorsal shell margin in Anatina are characters not present in Raeta. A lunule is defined in Anatzna, but not in Raeta; the antero-ventral swelling of the disk is less pronounced
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in Anatina; the corrugations are limited to the umbonal third of the shell in Anatina, but extend to the ventral margin in Raeta; the corcelet ridge is pronounced in Anatina, but its presence is indicated by a mere cessation of the corrugations near the post-dorsal margin, with no radial ridge per se in Raeta. In the right valve of Raeta, the anterior lamella is directly in line with the front ramus of the cardinal tooth, which is flat, and the ramus and lamella are separated by a notch (Figure 12). In A. ana- tina, the front ramus of the cardinal of the right hinge is bent above, almost as long as the front lamella, which is beside it and free from it below (Figure 10).
The vermiculate texture is common to both Anatina and Raeta. The periostracal chalk deposit, so pronounced in Anatina, may have become a lost character in Raeta s.s., but it is present in Raetina.
Raeta Gray, 1853
The genus Raeta Gray, 1853 (Ann. Mag. Nat. Hist., Ser. 2, vol. 11, p. 43) was briefly described and typed by original designation and monotypy, “R. campechensis’’,
which isa junior synonym of Lutraria plicatella LaMARCK, 1818.
Raeta plicatella (Lamarck, 1818) (Figures 11 to 13)
Lutraria plicatella Lamarck, 1818, Hist. Nat. Anim. sans Vert. 5: 470. Not figured; refers to GMELIN p. 3257, and CHEM- nitz Conch. Cab. 6, tab. 23, fig. 231 with a question mark. Type locality, “Probablement l’Océan indien.”
Lutraria canaliculata Say, 1822, Journ. Acad. Nat. Sci. Phila. 2: 311 - 312. Not figured. Type locality, “Maryland and as far south as East Florida.”
Mactra campechensis Gray, 1825, Ann. of Philos., N.S., 9: 135. Not described or figured; refers to “List. 304 (sic) f. 141”, evidently Lister, 1770, the second or Huddles- ford edition, where f. 141 of plate 308 (not 304) is a creditable figure of this species, with the words, “a sinu campeche” evidently indicating the type locality as the Bay of Campeche, Mexico.
Raeta perspicua Hutton, 1873. Cat. Marine Moll. New Zea- land, p. 65. Not figured. Type locality (erroneously) New Zealand. 1913, SurzrR, Man. New Zealand Moll., p. 970, Atlas (1915), plt. 60, fig. 5. Oxtver (1923: 184) notes that this is a synonym of R. canaliculata Say, incorrectly attributed to New Zealand:
Labiosa (Raeta) plicatella Lamarck. 1917, Lamy, Journ. de Conchyliol. Ser.-4,-42: 353 - 354; plt. 7, fig. 6 (photograph of holotype). 6%
The description and figures cited by Lamarck in de- scribing Lutraria plicatella were insufficient to recognize this species, and he furthermore thought it came from the
Indo-Pacific area, but expressed doubt. Lamy (1917) published a photograph of the holotype of Lamarck’s species which is unmistakably the species of the western Atlantic coasts. Meanwhile, it has been extensively cited in the literature under the trivial name applied by Say, and in combination with various generic names. HUTTON redescribed and named this species from a shell which he attributed to New Zealand, but which had evidently come from elsewhere, as pointed out by Oxtver. There are apparently no living species of Raeta or Raetella in New Zealand.
Figure 11
Raeta plicatella, dorsal view of shell 25 mm long, Galveston Beach. The hole was probably made by a shore bird.
Shell of moderate size (length 72, height 60, width 40 mm), thin, white, ovoid in side view, equivalve and gaping slightly behind; subequilateral, the umbos being slightly closer to the hind end. Umbos small, but swollen and prominent, touching each other and turned slightly but distinctly forward. The whole outer surface has prom- inent concentric ribs, rounded, poorly defined and with the grooves between slightly wider. These extend through the shell structure, producing a corrugated inner surface. In shells longer than 55 mm, the ribs tend to be more irregular and obliterated along the margin, with the inner surface smooth there. Fine radial wrinkles, closely spaced, are present on the ribs. These are most prominent on the lower third and hind slope of larger shells, where they extend into the grooves as well, and tend to anastomose. The wrinkles are part of the outer shell layer. The thin, light tan periostracum is smooth, closely adherent, but absent from even slightly worn shells. The front dorsal margin is gently convex, and continues in an even curve into the ventral margin, which is more convex. The hind dorsal margin has about the same curvature as the front, but it is shorter, slopes more abruptly from the hori-
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zontal; it meets the ventral margin in an obtusely rounded angle. There is no lunule; a narrow corcelet is poorly defined along the post-dorsal margin, extending to its post-ventral angle. This is formed merely by the con- centric ribs turning abruptly umbonad along this line, becoming much weaker, and lacking the vermiculate micro ridges present in front of the line.
The disk is greatly inflated from the umbo to the antero- ventral angle. A wide, shallow trough separates the disk from the post-dorsal slope, which is somewhat flattened.
The shell margin inside is smooth and sharp, the sur- face of the interior is subporcellaneous. The pallial line is thin, but prominent and continuous, with a large sinus reaching half-way forward and with rounded or usually acutely pointed tip. Its upper border has a rounded angle midway its length. The lower border is well separated from the pallial line proper. The anterior adductor muscle scar is thin and very elongate, narrowing acutely above.
Figure 12
Right (upper) and left hinges of Raeta plicatella. The tensiliar ligament is present in the left valve only, but the two halves of the resilium are present in their respective valves.
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The hind one is oval to subquadrate, with a small posterior pedal retractor scar confluent at its upper end.
The hinge plate is only slightly thicker than the rest of the shell. The hind half is vertical and flat, and of uniform width. It extends along the upper two-thirds of the hind margin. The front part has the shape of an acutely ta- pered triangle; it is about a third as long as the hind part. It is attached obliquely to the shell. Directly below the umbo there is a large triangular resilifer, deeply ex- cavated and extending to the tip of the umbo, but its upper third is covered by shell. The base of the triangle is well below the rest of the hinge plate margin. The lig- ament is entirely internal, and divided into resilium and tensilium, well separated. The resilium has the form of two tapering horns, slightly curved, with their apices in the covered upper parts of the resilifers, directly below the umbos, and the faces of their circular bases meeting in the midline. The faces of the opposed bases are con- cave, with only the peripheral margins touching. The concavity extends upward on the medial side of the horns to the tip of each. The outer, lateral side of each horn is flattened and about a third again as large as the opposing faces, so that the two halves of the resilium have the shape of an hour glass when viewed along the median plane of the animal.
The tensiliar part of the ligament is elongate lanceo- late, short, attached at the shell margin beginning just below the umbos, and with its axis sloping ventrally, away from the shell margin behind. Only the anterior tip is visible externally. The tensilium is attached to a hinge buttress, a lamella which parallels the hind side of the resilifer triangle, and which extends almost to the free hinge margin. It is obliquely attached to the hinge plate, so that its medial surface, to which the tensilium is at- tached, slopes downward and backward toward the resi- lifer cavity. Its upper third is attached to the shell margin completely roofing over the subumbonal tip of the trough on the hind half of the hinge plate. The lower half of the tensiliar lamella is acute, and extends over the trough slightly.
Along the tensiliar lamella, below the tensilium, there arises an oblique buttress lamella, of the hind ramus of the cardinal tooth. It completely conceals the upper fourth of the resilifer cavity, covering the apical end of the resilium. Along the margin of this lamella which ap- proaches the cardinal tooth, there is a sharp spine pro- jecting toward the middle of the base of the resilifer.
A single cardinal tooth in each valve has the shape of an inverted V, with the rami diverging at slightly less than a right angle, and the apex directly below the umbo, separated from it only by the thin hinge margin. The left cardinal fits into the cavity of the right one. The outer
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faces of the left cardinal are smooth and flat, but the two rami are thick and fused so that the cavity of its chevron is nearly filled solid, leaving only a vague medial sulcus on the ventral side. Each cardinal tooth is about half as high as the width of the hinge margin, and the hind ramus of each projects over the resilifer.
A deep groove along and above the base of each ramus of the left cardinal receives the right cardinal. This groove
Figure 13 Upper: Raeta plicatella from Galveston, 63 mm long. Lower: Raeta undulata from Topolobampo, Mexico, 71 mm long.
is formed behind by the margin of the subtensiliar butt- ress and its prominent spine, and in front by a lamella of moderate thickness, normal to the hinge plate and parallel to the anterior ramus of the left cardinal. This is the anterior lateral lamella. Its umbonal half is low, and connected to the inner side of the shell by a small buttress parallel to the hinge plate; this is the anterior buttress of the cardinal tooth and it reofs the extreme tip of the anterior hinge plate trough. The lower half of the anterior lamella is raised into a quadrate tooth-like process.
In the right valve the hind ramus of the cardinal tooth is fused with the spine of the buttress arising below the tensilium, but not completely, so that it and the spine appear as a bifid tooth. The front ramus is the same length as the hind one, but it appears to be twice as long, because of a quadrate lamella directly below and in line with it. It is separated from the quadrate lamella by a small but consistent notch. This quadrate lamella is the antero-lat- eral lamella. The front ramus of the right cardinal has a thick lamellar buttress extending from its free margin outward and upward to the inner surface of the shell, and roofing the trough of the hinge plate.
In both valves there is a single posterior lateral lamella, running from the umbo toward the ventral margin. This lamella is bent upward toward the shell margin, so that its attachment on the hinge plate is oblique, and poorly defined in medial view. Evidently these two lamellae are directly opposite each other in the closed shell, and one does not insert above the other, since neither crosses the median plane. But they may be homologous to the poste- rior lateral teeth of other mactrids.
Raeta (Raeta) undulata (Goutp, 1851) (Figure 13, lower shell)
Lutraria undulata Gou.p, 1851, Proc. Boston Soc. Nat. Hist. 4: 89. Not figured. Type locality: La Paz, Lower Califor- nia. 1853, Gouxp, Boston Journ. Nat. Hist. 6: 391; plt. 15, fig. 7.
Oxproyp (1924) has copied the English translation of the description by GouLp of this species which he pub- lished in 1853. She also republished (J. c., plt. 21, fig. 11) his original figure, an external view of a left valve. His figure 7 also includes a dorsal view of both valves, showing a prominent posterior gape. The figure he published shows very regular corrugations from beak to ventral margin, but in the larger specimens I have seen, these ridges tend to be obliterated toward the lower margin, more so than in Raeta plicatella. Perhaps his figure was drawn from a juvenile shell.
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The shell of Raeta undulata is similar to that of R. plicatella in the coarse corrugations well covered by ver- miculations, and in the hinge, which also has an oblique postero-lateral lamella in each valve. It differs chiefly in the more rounded, posterior end of the shell, in having the umbos about midway the length or slightly forward of that point, instead of well behind, and the corcelet line along the postero-dorsal shell margin is distinctly farther from the margin than in the east coast species. The chalk deposit of the periostracum seems to be absent. More extensive synonymies are given by Otsson (1961), all to secondary references however. This species may have the same ecological distribution as the one on the East Coast, just beyond the surf zone along sandy shores. KEEN (1958) notes that “Beach valves are fairly common, but entire specimens are hard to find, even by dredging”.
(Raetina) Dat, 1898
Raetina Dau, 1895, Proc. Malacol. Soc. London 1: 212, Type R. indica DALL (nom. nud.).
Raetina Dau, 1898, Trans. Wagner Free Inst. Sci. 3 (4) : 822, Type by O. D. and M Raeta (Raetina) indica Datx, 1898, which is a junior synonym of Mactra pellicula REEVE.
This is similar in size and shape to Raeta s.s. The hinge plate is thick, almost vertical behind, and the groove on it is shallow and rounded in cross section. Sculpture is continuous top to bottom, and from front to hind end; it consists of corrugations evident on the inner surface of the shell, and the corrugations are in line with the growth lines, not oblique. Vermiculate texture is present, but very weak and limited in area.
The main reasons for recognizing this as a distinct sub- genus are two: (1) the sculpture is more delicate, the corrugations being finer and more closely spaced than in the typical subgenus; (2) the posterior lamella, running obliquely from the umbo across the front end of the hind hinge plate, is absent in this subgenus. Chalky deposits in this periostracum, which occur in Anatina, may be present in Raetina, but seem to be absent in Raeta s. s.
This genus was essentially a nude name as of 1895, diagnosed only by indication of the type species, which was not described until 1898.
Raeta (Raetina) pellicula (REEvE, 1854) (Figures 14 and 15)
Mactra pellicula “DEsuayEs” Reeve, 1854 (May). Conch. Icon 8: Monograph Mactra, plt. 21, fig. 124. Type locali- ty: Japan.
Mactra anatinoides Reeve, 1854. Conch. Icon. 8: Monograph Mactra, plt. 21, fig. 123. Type locality unknown.
Mactra pellicula DesuayeEs, 1855. Proc. Zool. Soc. London 22: 68. Not figured. Type locality: “Japan (col. Cuming) .”
Raeta grayi H. Avams, 1872. Proc. Zool. Soc. London, p13; pit. 3, fig. 23. Type locality: Borneo.
Raeta abercrombiei Metviti, 1893. (In MEtvitt &« ABER- cromBIE, 1893) Manchester Lit. & Philos. Soc. Mem. & Proc. Ser. 4, 7: 32 (nom. nud.) ; MrtviLx, 1893, Ibid., p. 65; plt. 1, fig. 25. Type locality: Bombay, India.
Raeta (Raetina) indica Daur, 1895. Proc. Malacol. Soc. Lon- don 1: 212 (nom. nud.) .
Raeta (Raetina) indica Dat, 1898. Trans. Wagner Free Inst. Sci. 3 (4) : 882 - 883, footnote. Not figured. Type locality: Bombay, India.
Anatina (Raetina) indica Dau, 1925. Proc. U.S. Nat. Mus. 66 (17): 2; plt. 20, fig. 2. Holotype.
Raeta jickelii Sturany, 1905. Nachrichtsbl. d. deutsch, Mala- kol. Ges. 37t year, pp. 133 - 134; text figs. a, b, and c, p. 133. Type locality: “Massaua” (Massawa, Ethiopia, south- west coast of the Red Sea).
Raeta magnifica Yokoyama, 1922. Journ. Coll. Sci. Tokyo, 44: 132; plt. 8, figs. 12, 13. Type locality: Fossil, Tega (Kizaki), Japan.
Raeta fragilis GraBau & Kinc, 1928. Shells of Peitaiho, pp. 190 - 192; plt. 7, fig. 54. Type locality: Peitaiho (Yellow Sea, China).
This species has a very wide range, from the shores of the Red Sea, to India, Borneo, China and Japan. It evi- dently shows some variation in form, particularly in the
Figure 14
Holotype of Raeta (Raetina) indica Dart (= Raeta pellicula). The dark shading along the postero-dorsal margin indicates peri- ostracal chalk deposit. Length, 43 mm.
length and acuteness of the rostrum. The short-rostrate forms are what authors have called Raeta anatinoides (REEVE) and, judging from the figure, R. grayi H. Apams. ToMLIn (1924) pointed out that the species names pub-
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lished by Reeve (1854) in his monograph of Mactra predate all species named by DESHAYES in 1854 and 1855, even though REEvE attributes many names to DESHAYES. For exact date on the several species, see the paper by Tomun. Elsewhere Tomun (1931) declares R. aber- crombici identical with R. grayi after comparing the holo- types of the two species. Although Dati was quite sure his R. indica was distinct from R. abercrombiei, the only differences he cited were “form and proportion”. The holotype of R. indica Dat shows nosignificant differences from a shell in the National Collection from Japan, which in turn fits quite well with the concept of R. pellicula Reeve. No one who has studied the group seems to have seen more than a few shells from different places, and the above synonymy can only be tentative.
Figure 15 Interior of same valve as shown in Figure 14.
Like the species of Raetas. s., all records of this species are from the beaches of continents or the larger conti- nental islands. It may be absent in the small oceanic is- lands of the Indo-Pacific, which seem indeed to have few mactrids of any genus. Probably this species lives at the outer edge of the surf zone on sandy shores.
The following description is based on the holotype of Raeta indica Daut, which is a single left valve, USNM 90276, with the words “Bombay” and “Wesleyan Univ.” on the label.
Length 43, height 28, semidiameter 9 mm. Shell elon- gate ovoid, front end evenly rounded, hind end drawn out in an obtusely rounded rostrum. Probably equivalve, and almost equilateral, the umbos being slightly closer to the front end. Umbos prominent, touching, turned slightly forward. Shell very thin, translucent, with numer-
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ous concentric ribs and troughs, which are undulations of the shell substance affecting both surfaces. The undula- tions are regular, from umbo to ventral margin, and con- tinuous, except along the post-dorsal slope. They are parallel to the growth striae. Color white. No lunule. Corcelet (or escutcheon?) defined only by rapid dimi- nution of the ribs along a poorly defined line near and parallel to the post-dorsal margin. No epidermis is evident, but there is a chalky white deposit postero-ventrally. A few faint vermiculations, similar to those of Raeta plica- tella, are evident only along the post-ventral part of the valve.
The roundly pointed pallial sinus reaches as far for- ward as the umbo. Its lower margin is separated from the pallial line. Muscle scars could not be seen in the slightly worn holotype (but Datu illustrated them as typical of Raeta s.s.). The hinge is typical of Raeta, except that there is no hind radiating lamella between the resilifer and the groove of the post hinge plate. The com- parable buttress of the front hinge plate groove is slightly broken, but it has a thick base. The posterior gape between the valves must have been small.
I cannot see any specific differences in the holotype and a pair of matched valves from Japan (Hirase Coll., US NM 344967, 53 mm long, 41 mm high). The Japanese specimen is larger, not as acuminately rostrate behind. There is no chalk deposit on its posterior slope, but a faint, narrow corcelet ridge seems to be present, slightly forward of the line medial of which the concentric ribs become mere growth striae, though pronounced.
The form of both the Indian and Japanese shells is easily distinguishable from Raeta plicatella and R. undu- lata, the ribs are more numerous and finer, the posterior lateral lamella is lacking in both specimens of the oriental species.
Raetella Datu, 1898
Raetella Dax, 1895. Proc. Malacol. Soc. London 1: 212. Type by O.D. and M. Raetella tenuis (Hinps MS.) Day (nom. nud.) .
Raetella Dau, 1898. Trans. Wagner Free Inst. Sci. 6 (4): 882 - 883. Type species by O. D. Raetella tenuis “Hinps” Dat, 1898, which is a junior synonym of Poromya pul- chella A. ADAMS & REEvE, 1850.
Raetellops Hae, 1952. Genera of Japanese Shells, Pelecypoda No. 3: 197, as subgenus of Raeta Gray, 1853. Type by O.D., Poromya pulchella A. ApaMs & REEvE, 1850.
This name was essentially nude when proposed by Dati in 1895, being diagnosed only by designation of the type species, which was not described until 1898.
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Shells of this genus are much smaller in size than those of Raeta, and the ribs of Raetella are proportionately coarser. They are, moreover, slightly oblique to the lines of growth. The shells have a peculiar opalescent luster, which Datu called a “‘pseudo-nacreous surface”. Vermi- culate texture and chalky periostracal deposit are absent. Although Dati (1898, p. 882) said the “dorsal areas [are] well defined”, there is no structural feature on the external surface defining them; their presence is merely simulated by the attachment of the hinge plate showing through the translucent shell. The hinge plate lamellae are very thin, and the front one is only slightly shorter than the hind one. Both front and hind parts are almost horizontal, with the space between them and the adjacent valve surface very deep. In Raeta and Raetina the posterior half of the hinge plate is essentially vertical and thick, with swollen, rounded free margin. The lateral teeth are paral- lel to the hinge plate margin, not strongly oblique to it, as in Raeta and Raetina. Moreover, there is a single hind lateral in the left valve, but two in the right, in the pattern quite general in Mactridae. But there is only a single, short antero-lateral in each valve. This genus may extend to greater depths than do Raeta or Raetina, which, like most mactrids, are shallow water inhabitants. As presently known, it seems limited to the eastern coast of Asia and larger continental islands along it.
Raetella pulchella (A. ADAMS & REEvE, 1850) (Figures 16 to 19)
Poromya pulchella A. ADAMS & REEVE, 1850. Voy. Samarang. Zool., Mollusca, p. 83; plt. 23, fig. 1. Type locality: Shores of Borneo.
Mactra rostralis “DESHAYES” REEvE, 1854. Conch. Icon. 8, Monogr. Mactra, plt. 21, fig. 119. Type locality: “China Seas?”
Mactra rostralis DEsHaYEs, 1855. Proc. Zool. Soc. London, p. 69. Not figured. Type locality: Japan.
Raeta yokohamensis Pirssry, 1895. Cat. Marine Moll. Japan
. collected by F Stearns, p. 119; plt. 3, figs. 4, 5. Type locality: Yokohama, Japan.
Raetella tenuis “Hinps” Datu, 1898. Trans. Wagner Free Inst. Sci. 3 (4): 883 (footnote). Not figured. Type locality: Hong Kong Harbor, about 8 feet of water.
Raeta elliptica Yokoyama, 1922. Journ. Coll. Sci. Tokyo 44: 131 - 132; plt. 8, fig. 7. Type locality: Fossil, Tega, Ka- menari, Kioroshi (Japan). ;
Raetella rostralis has been considered a synonym of R. pulchella by most authors, as pointed out by Lamy (1917). On the basis of the original descriptions and illustrations of the several nominal species, I agree with Hape (1952) that Raeta yokohamensis and Raeta elliptica should be added to the synonymy. The specimen on which Dati
based his name Raetella tenuis ““Hinps” also seems con- specific. Hinps seems never to have named such a species, and Dau (1898) received the name from P. P. Carpenter, who evidently took it from a label in the British Museum.
The following description is based on the holotype of Raetella tenuis “Hinps” Datu. The type lot is USNM 519, and the label has written on it “4-8 ft., mud, in har- bor, Hong Kong, Stimpson”. The holotype consists of disjoined valves of one shell; the right valve is only broken around the ventral and posterior margin, but the left is fragmented into several large pieces.
Shell small (13 mm long, 10mm high, 3.0 mm semi- diameter), ovate in profile, evenly rounded in front and
Figure 16
Holotype of Raetella tenuis “Hinps” Dati (= Raetella pulchella) . Length, 13 mm.
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below, drawn out in a short but rather acute rostrum behind. The disk is very inflated, almost hemispherical, but the inflation is even, without a prominent axis from umbo to antero-ventral margin. Umbo 5/7 the length from the front end.
Color white. A thin, closely adhering periostracum is light tan. The outer surface has a faint opalescent irides- cence. Sculpture of about 23 concentric ribs, which are regularly spaced from umbo to ventral margin, but which do not extend to the antero-dorsal margin nor onto the rostrum. There is a slight, very broad, shallow sulcus be- tween the disk and the post-dorsal region, but no demar- cation of an escutcheon or corcelet. There is no chalky deposit in the periostracum, and no radiating vermiculate texture. The concentric ribs are slightly oblique to the lines of growth, and this is most prominent on the antero- ventral part of the disk. A lunule is simulated by the attachment of the anterior hinge plate.
Shell very thin, the ribs forming undulations on the inside, which is porcellaneous. Attachment scars not evi- dent in the holotype.
Figure 17
Hinge of holotype of Raetella tenuis “Hinps” Dati (= Raetella pulchella)
In the right valve a V-shaped cardinal tooth is adjacent to and points toward the umbo. The two arms are about equal in length, moderately thick, and with a broad, deep space between them. A deep cleft separates the medial part of their junction, at the apex of the V (poorly shown in Figure 17; see Figure 19). The posterior arm is separated by a narrow space from the front edge of the resilifer. Along the base of the anterior ramus there is a very thin buttress which crosses obliquely the space
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Figure 18
Upper: Raetella pulchella from Japan (USNM 249247) showing
pallial sinus. Lower: Raetella pulchella from Fukura, Awaji, Japan
(USNM 344966) 23 mm long. Note relatively smooth surface and poorly rostrate hind end.
over the cavity of the anterior hinge plate and attaches to the shell. A lamella in line with the anterior arm of the cardinal and also the anterior hinge plate lamella seems to be broken off, flush with the latter, in the right valve of the holotype (see Figure 19). The anterior hinge plate is very thin, with sharp free margin. It is almost horizon- tal, paralleling the dorsal margin of the shell and at- taching rather far laterally. The cavity between the front hinge plate and the shell is thus very deep and narrow. The front hinge plate lamella is only slightly shorter than the hind one. The hind hinge plate is not so wide as the front, and the cavity between it and the shell is not so deep. No escutcheonal area is defined on the outer sur- face by its attachment. It is equally thin, with sharp margin. Along the umbonal fourth this plate is extended medially slightly, forming a lateral tooth. Above it on the margin of the shell is another very slight lamella, not as long as the lower one, forming an upper posterior lateral tooth. The resilifer is small, triangular, directed down- ward from the umbo. Tensilium very short, directly under the umbo, and not separated from the resilifer by any shelly material except the small ledge on which it sits.
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Hinge of the left valve similar to that of the right. The two rami of the V-shaped cardinal tooth are thicker, smaller, and evidently fit inside the right cardinal. Above the left cardinal and between it and the umbo is a small but prominent tooth-like process, with an inverted V- shape, the front ramus of which is very short. The hind ramus of this little tooth margins the upper part of the resilifer. A lamellar extension of the anterior hinge plate seems to be present at the umbonal end but it is badly broken. There is no dorsal lateral tooth on the shell mar- gin. A very thin prominent lamella radiates from the umbo and separates the hind hinge plate from the cardinal area. Two small lamellae in the front hinge plate cavity of the left valve do not extend to the median plate of the shell, and are possibly abnormal.
~~ Cho ee Z ~~ 5 Sy? Sas Bae
SNS ae eee nS Ses i LELEF
SWS al =
Figure 19
Hinge of Raetella pulchella from Japan (USNM 249247). The drawings were made at slightly different angles, causing the resilifer of the left (lower) valve to appear smaller than that of
right hinge.
The holotype of DaLt’s nominal species is more inflated over the disk and more rostrate behind than most speci- mens of the 14 lots in the National Collection from Japan. It fits the concept of “Mactra” rostralis better than “M.”’ pulchella, but I think it is only an extreme variant of this highly variable species (cf. Figure 18). Some shells from Japan are larger (20mm long, 14mm high). The Japanese shells are slightly gaping behind, and equivalve. Sculpture on them varies considerably, some shells being almost smooth, with ribs limited to the ventral part, not present on the umbo. Most Japanese shells are less rostrate
behind than is the holotype of Da.t’s species; they are more equilateral, and not as inflated over the disk.
Figure 19 is a drawing of the hinge of a Japanese specimen, showing the prominent short anterior lateral tooth, directly on the hinge plate margin. Each tooth curves outward from the umbo, as shown by the dotted lines at their bases. The left antero-lateral slips above the right one when the valves close. The left valve has a single postero-lateral tooth, which fits between the two on the right valve. All these postero-laterals are developed as elongate lamellae directly on the valve margin and hinge plate margin, and parallel to them.
A large lot from Siam (USNM 477293) has very thin shells which are non-rostrate, well sculptured, and of a uniform small size.
SPECIES INCERTAE SEDIS
Raeta meridionalis Tate, 1889 (Figure 20)
Raeta meridionalis Tate, 1889. Trans. Proc. Roy. Soc. South Austral. 11: 61; plt. 11, fig. 3. Type locality: Aldinga Bay (South Australia).
?Labiosa meridionalis Tate, 1889. HEpLEy, 1900. Proc. Linn. Soc. New South Wales 25: 497; plt. 25, figs. 5 - 9. Locali- ty: Chinaman’s Beach, Middle Harbour (Australia).
Tate’s original description of this species is here quoted, and Figure 20 (left) is a tracing of his original drawing.
“Shell whitish, very thin, translucent; ovately-suboblong, mod- erately convex antemedially, posteriorly gaping; umbo sub- acute, curved forward, situated in the anterior three-sevenths. “Anterior margin regularly rounded, ventral margin strongly arched; dorsal line sloping on both sides, more so in front than behind; posterior side narrowed and depressed, its margin somewhat squarely truncated and slightly reflected. There is an ill defined depressed post-dorsal area, but no umbonal ridge. “Sinus widely rounded, horizontal, reaching to the center, visible on the exterior.
“Surface marked by fine lines of growth, which become more conspicuous and finely wrinkled on the post-dorsal area. “Dimensions: Antero-posterior diameter, 35; umbo-ventral di- ameter, 30; sectional diameter of left valve, 8 millimeters. “Locality — one valve collected by Mr. Magarey on the beach of Aldinga Bay.”
The species described by Tate has the shape of Mactra anatinoides REEVE, which I have considered a junior syn- onym of Raeta pellicula. But the sculpture is most un- usual for a Raeta. It is apparently so thin that the pallial sinus shows through the shell, yet strong concentric cor- rugations seem to be lacking, and there is no corcelet line or ridge along the post-dorsal slope. I have seen no speci- mens. This species evidently lives near the shore of sandy
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beaches and it may be quite rare. A copy of the original figure is given by Cotron & Goprrey (1938) and by ALLEN (1959). Incidentally, Cotron’s (1961, p. 343) reference to the original description of this species (“TATE, 1887, Trans. and Proc. Roy. Soc. So. Austr. 9: 68 - 69, pl. 5, fig. 4, Montacuta meridionalis’) is evidently in error, for the description and figure of Montacuta meridionalis Tate, 1887 clearly refers to a leptonid bivalve, and not to R. meridionalis (Tate, 1889).
PL. XXV.
7 eS es / Cae — rE 2) SSS Sere —— LG fy \) i ee i if Bile “ , 4 Y if [ : Hai AAv! nti Wo zat Wo yy as Hl 4 9S ye Figure 20
Left: Tracing of figure 3 of plate 11, TaTE, 1889, the original drawing of Raeta meridionalis Tate. Right: Figures 5-9 of plate 25 of HEDLEY, 1900, which he also identified as Raeta meridionalis TATE.
The problem is further confused by the account Hep- LEY (1900) gave of 14 additional specimens which he found. Although his shells were reported to be authenti- cated by Tate, the size, shape and sculpture all suggest a species of the Raetella pulchella group. The peculiar drawing of the sculpture also suggests the concentric undulations are slightly oblique to the lines of growth, as in Raetella, and not vermiculate textural features char- acteristic of Raeta and Raetina. HeDLEy’s remarks and figures are here reproduced (Figure 20, right).
“This species has hitherto been known from a single valve found on the beach of Aldinga Bay, South Australia. This year I have taken a whole shell containing part of the animal, and on another occasion a broken valve on “Chinaman’s Beach”, Middle Harbour. Prof. Tate, to whom one valve was submitted, kindly informs me that there is no essential difference between it and the type of meridionalis. My specimens are smaller, being 28 mm in length and 21 mm in height. Being perfect, I have utilized my example to draw the valves in apposition and other details not obtainable from the single valve hitherto known.
“Though disagreeing by vermiculate sculpture, the species seems to me nearer to the subgenus Raetella, DALL, than to any other division of Labiosa.”
Possibly there are two species along the shore of south- ern Australia, one described by HeEpxey being similar to Raetella pulchella, the other to a sub-oval Raeta (Rae- tina) pellicula. SMrrH (1914, p. 150) cites Cypricia grayi H. Apvams (which is Raeta grayi H. ApaMs cited above in the synonymy of Raeta pellicula) from Queensland, Australia, and notes a reference which I have not seen, which does the same (HeEptey, 1910, Rep. Austral. Assoc. Adv. Sci. for 1909, p. 351).
Nick es (1950, p. 209) cites a “Labiosa vitrea Gray” from the west coast of Africa (“Casamance a la Guinée frangaise; Congo frangais”), with a brief description and figure. The general shape is that of Raetella, but the size is larger (up to 50 mm long). There are regular undula- tions only on the posterior slope, which is unusual for this genus. This is possibly Mactra vitrea Gray, 1837 (Charlesworth’s Mag. Nat. Hist., New Ser., vol. 1, p. 372, not figured) described from unknown locality. Lamy (1917, pp. 273 - 274) placed this in the subgenus Mact- rinula of Mactra, but did not figure or describe it, nor did he know the locality of the material which he examined in the Paris Museum. I have seen no specimens, and cannot comment on its possible membership in Anatina or Raeta.
As Lamy (1917) has noted, Raeta lyrata “Hinps Ms.” H. « A. Apams (1856) is a nomen nudum, and Raeta bracheon Sturany, 1899 (p. 12; pl. 3, figs. 1-6; Gulf of Suez, 50 fathoms) belongs elsewhere. Lamy says it is Leptomya cochlearis Hinps, of the Scrobiculariidae.
The Raeta tenera “DESHAYES” listed by H. & A. ADAMS possibly refers to “Mactra tenera Desh.” listed as a syn- onym of Mactra anatinoides, with query, by Reeve. As Tomutn (1924) implies, no such species seems to have been described by DEsuay Es.
According to the Zoological Record, Li (1930) de- scribed a new species, Raeta maxima, but I have been unable to locate that article.
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SYSTEMATIC DISCUSSION
Much essential information relevant to the phylogeny and life habits of this group is likely to be gained by further investigation of their anatomies. There are also characters of the shell which have not been given adequate atten- tion. Admittedly, the species of this review were chiefly considered on the basis of those traditionally grouped to- gether. Anatomical studies on these and other mactrid species may well indicate revisions of the classification quite different from that proposed by Dax (1895, 1898) and expanded by Lamy (1917). Several examples of shell characters whose significance is unexplored occurred to me during the present study. One is that thin-shelled mactrids generally have corrugated concentric sculpture, with the ridges affecting both the inner and outer shell surface, as in Raeta and Raetella, or they have a keel along the post-dorsal slope as in Anatina, Mactra alata, and M. fragilis; this keel I have called a corcelet, although aware that it may not be homologous to structures so named in other families. Perhaps the corrugations and keel are devices which strengthen the shell. In some species both are present, notably Harvella elegans from the tropical part of the western shores of the Americas. Mactra iheringi (Dati, 1897), from the east coast of South America, is very similar to H. elegans in size, shape and dentition, but it is a much thicker shell, with smooth external surface and no corrugations or post-dorsal ridge. That these two represent analogous species on the two sides of the continent should be given further study.
Incidentally, Harvella elegans seems to have vermicu- late texture similar to that of Raeta plicatella, and the distribution of this feature among thin-shelled mactras with corrugated shells should be studied.
In a rare species of the Indo-Pacific, Mactra (Mactrin- ula) plicataria Linnaeus, 1767, the front end of the shell is disproportionately elongate, with the hind end trun- cated, and a form recalling Donax. This genus has further developed a thin shell, with corrugate sculpture and ver- miculate texture very similar to Raeta. The disk, however, is not exceptionally swollen.
In the group of Anatina, Raeta, and Raetella there is a more pronounced swelling of the disk, which is not me- dial, but extends more toward the front end of the shell. In its extreme form, such as found in Raeta s.s., a shape recalling that of Cuspidaria results. This is just the op- posite of the disk swollen along a line running postero- ventrally such as found in the Mytilidae and Carditidae.
Raetella may be no more closely related to Raeta and Raetina than any of them are to Harvella or Mactrinula. The sculpture of Raetella recalls that of the West Ameri- can Tumbeziconcha, which, however, has the posterior
end of the shell extended, and the obliquity of the ridges on that end, rather than on the front one.
LITERATURE CITED
ApaMs, ARTHUR & LoveLL Aucustus REEVE 1848-1850. The zoology of the voyage of H.M.S.Samarang, under the command of Captain Sir Edward Belcher. Mollusca. London, prts. 1-3: 1-87; 24 plts. ApaMs, HENRY 1872. Descriptions of fourteen new species of land and marine shells. Proc. Zool. Soc. London for 1872: 12-15; plt. 15 (June 1872) ApaMs, HEnry, « ARTHUR ADAMS 1853-1858. The genera of Recent Mollusca, arranged according to their organization. London; 1: vi-xl, 1-484; 2: 1-661: 3: plts. 1 - 138 ALLAN, Joyce K. 1950. Australian shells. Georgian House, Melbourne; 470 pp. Bosc, Louis AucusTIN GUILLAUME 1816. Anatine. In: Nouveau dictionaire d’histoire naturelle. vol. 1, p. 492. Deterville, Paris Cotton, BERNARD CHARLES 1961. South Australian mollusca. Adelaide, 363 pp. Cotton, BERNARD CHARLES & FRANK K. GopFREY 1938. The molluscs of South Australia. Part I - Pelecypoda. Frank Trigg, Govt. Printer, Adelaide, 314 pp. Dai, WILLIAM HEALEY 1895. Synopsis of a review of the genera of Recent and Ter- tiary Mactridae and Mesodesmatidae. Proc. Malacol. Soc. London 1 (5): 203 - 213 1890-1903. Contributions to the Tertiary fauna of Florida. Trans. Wagner Free Inst. Sci. 3 (1-6): 1654 pp.; 60 plts. [part 4, 1898, contains the data relevant to the present study]. 1898a. Note on the anatomy of Resania, Gray and Zenatia, Gray. Proc. Malacol. Soc. London 3 (2): 85 - 86 1925. _ Illustrations of unfigured types of shells in the collection of the United States National Museum. Proc. U.S. Nat. Mus. 66: 1 - 41; plts. 1 - 36 Desuayes, GERARD PAauL 1855. Descriptions of new species of shells, from the collection of Hugh Cuming, Esq. Proc. Zool. Soc. London for 1854 22: 62-72. (Forty seven new bivalves, all in Mactridae, are described. See Tomtin, 1924). (10 February 1855) GouLp, Aucustus ADDISON 1851. Descriptions of new shells from California, collected by Maj. William Rich and Lieut. T. P Greene, U.S.N. Proc. Boston Soc. Nat. Hist. 4: 87 - 93 1853. Descriptions of shells from the Gulf of California and the Pacific coasts of Mexico and California. Boston Journ. Nat. Hist. 6: 374 - 407; plts. 14 - 16 Gray, Joun Epwarp 1825. A list and descriptions of some species of shells not taken notice of by Lamarck. Ann. of Philos., New Ser. 9: 134 - 140; 407 - 415
W. L. Hawes, Govt. Printer
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Gray, JoHN Epwarp, cont.
1837. A synoptical catalogue of the species of certain tribes or genera of shells contained in the collection of the British Mu- seum and the author’s cabinet; with descriptions of the new species. Charlesworth’s Mag. Nat. Hist. 1 (new ser.) : 370 to 376
1853. A revision of the genera of some of the families of con- chifera or bivalve shells. Ann. Mag. Nat. Hist., Ser. 2, 11: 33 - 44
Hase, TADASHIGE
1952. | Genera of Japanese shells.
187 - 278 HeEpDLEY, CHARLES
1900. Studies on Australian Mollusca, Part 2.
Soc. New South Wales 25: 495 - 513; plts. 25, 26 Hutton, FREDERICK WOLLASTON
1873. Catalogue of the marine Mollusca of New Zealand with diagnoses of the species. Wellington (Colon. Mus. & Geol. Surv. Dept.) pp.i-xiv+1-116; 1 plt. (after 7 May 1873)
Hyman, Lissy HENRIETTA
1951. The invertebrates: Platyhelminthes and Rhynchocoela,
vol. 2, 550 pp., McGraw-Hill, New York Keen, A. Myra
1958. Sea shells of tropical West America; marine mollusks from Lower California to Colombia. i-xi + 624 pp.; illus. Stanford, Calif. (Stanford Univ. Press)
1961. | What is Anatina anatina? The Veliger 4 (1): 9 to 12; 5 text figs. (1 July 1961)
Kettocc, James LAWRENCE
1915. Ciliary mechanisms of lamellibranchs with descriptions
of anatomy. Journ. Morphol. 26: 625 - 701. Lamarck, JEAN-BartisTe PreRRE ANTOINE DE MONET DE
1818. Histoire naturelle des animaux sans vertébres.
Paris, 7 vols. Lamy, EpouaRD
1917-1918. Revision des Mactridae vivants du Muséum d’Histoire Naturelle de Paris. Journ: de Conchyl. 63 (3) : 173 - 275; and (4): 291-411; 2 plts.
Li, C. CHanc
1930. The Miocene and Recent Mollusca of Panama Bay.
Bull. Geol. Soc. China, Peking 9 (3): 249 - 279; plts. 1-8 ListER, MartTIN 1685. Historiae sive synopsis methodicae conchyliorum.
Pelecypoda No. 3, pp.
Proc. Linn.
London, 466 pages of plates. [Neither the pages nor the plates, sometimes several to a page, are numbered in the original edition. The figures are numbered consecutively within each of several chapters. The U.S. National Museum copy of the first edition was autographed by Lister and presented to the Earl of Pembroke, and later owned by Deshayes and Dall. A second edition, published in 1770 by William Huddesford, Oxford, contains an index, but it is not consistently binomial. The several plates on each page have been given numbers, as well as retaining the original numbers of the figures. Plate 308 (not 304) has figure 141.]
MELVILL, James Cosmo 1893. Descriptions of twenty-five new species of marine shells from Bombay collected by Alexander Abercrombie, Esq. Manchester Lit. & Philos. Soc. Mem. & Proc., Ser. 4, 7: 52 - 67; 1 plt. (reprinted in Journ.. Bombay Soc., 8: 234 - 245; plt. 1, fide Zool. Rec.)
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MELVvILL, JAMES Cosmo & ALEXANDER ABERCROMBIE 1893. | The marine Mollusca of Bombay. Manchester Lit. & Philos. Soc. Mem. & Proc., Ser. 4, 7: 17-51 (reprint pages renumbered 1 - 35) Moore, Hitary Brooke 1931. The systematic value of a study of molluscan faeces. Proc. Malacol. Soc. London 19 (6): 281 - 289; plts. 31 - 33 Nickiés, Maurice 1950. Mollusques testacés marins de la céte occidentale d’Af- rique. Man. Ouest-Afr., 2: i-x+1-269; 459 text figs. Paris, Lechevalier Otproyp, Ipa SHEPARD 1924. The marine shells of the west coast of North America. Stanford Univ. Publ. Geol. Sci., 1: 1-247; plts 1-57 Otiver, W.R. B. 1923. Notes on New Zealand pelecypods. Soc. London 15: 179 - 188 Otsson, AXEL ADOLF 1961. Mollusks of the tropical eastern Pacific, particularly from the southern half of the Panamic-Pacific faunal province (Pan- ama to Peru). Panamic-Pacific Pelecypoda. Paleont. Res. Inst. Ithaca, N. Y, 574 pp.; 86 plts. (10 March 1961) PELSENEER, PAUL 1911. Les lamellibranches de lexpédition du Siboga. Partie anatomique. Siboga-Exped. 53 a: 1 - 121; 26 plts. Pitssry, HENry AUGUSTUS 1895. Catalogue of the marine mollusks of Japan with de- scriptions of new species and notes on others collected by Fred- erick Stearns. Privately printed, Frederick Stearns, Detroit, pp. i- viii+ 1-196; 11 plts. Reeve, Lovett Aucustus 1854. | Monograph of the genus Mactra. In: Conch. Icon. 8. Lovell Reeve, London. (consists of 21 numbered plates, with explanations and descriptions on unnumbered facing pages. At the bottom of each page of explanation is the month and year of pub- lication; all are March, April, or May 1854). Riwewoon, W. G. 1903. On the structure of the gills of the Lamellibranthia. Phil. Trans. Roy. Soc. London (B) 195: 147 - 284 Say, THOMAS 1822. An account of some marine shells of the United States. Journ. Acad. Nat. Sci. Phila. 2: 221-248, 257-276, and 302-325 SmirH, Epcar ALBERT 1914. A list of Australian Mactridae, with a description of a new species. Proc. Malacol. Soc. London 11 (2): 137 - 151 SouTHWELL, T. 1925. A monograph of the Tetraphyllidea with notes on re- lated cestodes. Liverpool School of Trop. Med. Memoir (n. ser.), no. 2, 368 pp. Sturany, RupoLF 1899. Lamellibranchiaten des Rothen Meeres. In Expedi- tion S. M. Schiff “Pola” in das Rothe Meer. Zool. Ergeb. 14: 1-41; plts. 1-7 1905. Beitrage zur Kenntnis der Molluskenfauna des Roten Meeres und des Golfes von Aden. Nachrichtsbl. d. deutsch. Malakozool. Gesellsch. 37 year: 132-146 Tate, RatpH 1889. Descriptions of some new species of marine Mollusca from South Australia and Victoria. Trans. Proc. & Reprt. Roy. Soc. South Australia 11: 60 - 66; pit. 11
Proc. Malacol.
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TomLin, JoHN Reap LE BrocKToN 1924. Notes on some Mactridae. Journ. Conchol. London 17 (5): 134 - 136 (he notes that Reeve’s monograph on Mactra appeared before all names published by DesuHayEs in this group, including those attrib- uted to DEsHAYEs by REEVE) 1931. Raeta abercrombiei Metvitt. Journ. Conchol. Lon- don 19 (4): 111 Vokes, Harotp E. 1967. | Genera of the Bivalvia: a systematic and bibliographic catalogue. Bull. Amer. Paleont. 51 (232): 105 - 394 Woop, WILLIAM 1828. Supplement to the Index Testaceologicus or a catalogue of shells, British and foreign. London, W. Wood. 59 pp.; 8 plts. (consists of names, without authors, on the explanation of the plates; the names should be attributed to Woop unless an earlier source can be found.) Yokoyama, MataJIRo 1922. Fossils from the Upper Musashino of Kazusa and Shim- osa. Journ. Coll. Sci. Imp. Univ. Tokyo 44 (1): 1-200; pits. 1-17 YoncE, CHarLes MAurIcE 1948. Cleansing mechanism and the function of the fourth pallial aperture in Sprsula subtruncata (pA Costa) and Lut- raria lutraria (L.). Journ. Mar. Biol. Assoc. Plymouth 27: 585 - 596
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A New Species of Gastropod (Fissurellidae, Fissurisepta)
from the Eastern North Pacific Ocean
IAN McT. COWAN
Faculty of Graduate Studies, The University of British Columbia, Vancouver 8, British Columbia, Canada
(3 Text figures)
Fissurisepta SEGUENZA, 1863, Is CUSTOMARILY regarded as a subgenus of the genus Puncturella. This designation has been based upon characteristics of the shell, and the living animal seems never to have been described. Recently the discovery of a single living specimen in a dredge haul from 470 fathoms off the west coast of British Columbia not only extends the known distribution of the subgenus into the eastern Pacific Ocean but also permits reexamina- tion of its systematic status on the basis of some soft-parts anatomy.
The type species, Puncturella (Fissurisepta) papillosa SEGUENZA, 1863, is known only from the Miocene of Sicily and adjacent regions. A second species of the sub- genus, P (F}) rostrata SEGUENZA, 1863, was described from the same deposits. A third species of Miocene occurrence was described as P (F) retula Wooprina, 1928. His speci- mens were from Jamaica.
At almost the same time the subgenus was discovered as a fossil it was found in the living fauna off Norway (JEFFREY, 1882) and described as Puncturella (Fissuri- septa) granulosa JEFFREY, 1882. Subsequent explorations have yielded specimens from several parts of the Atlantic. Thus P(E) acuminata Watson, 1833, was taken off North Culebra Island in the West Indies, and again off Yucatan and off Cumberland Island, Georgia. Specimens from the two last localities were described by Dati (1889) as Fissurisepta triangulata, a name now regarded as a syn- onym of P (F) acuminata (FarFanTE, 1947). This species was collected again off the Azores where it provided the source of yet another apparent synonym microphyma DAUTZENBERG & FiscHER, 1927 (FARFANTE, 1947).
A second species from the West Atlantic off Georgia was named by Dati (1927) as Puncturella tenuicula. CiarKE (1962) has named a 5" species from the Atlantic as Puncturella (Fissurisepta) agulhasae.
Fissurisepta was unknown in the Pacific until 1951 when Kuropa named and described the shell details of Punctu- rella (Fissurisepta) soyoae from Japanese waters. More recently OkuTANI (1964) has reported a second species, P. (F) undulata from the western Pacific Ocean.
The bathymetric range of this creature, with one excep- tion, has extended from 200 fathoms down to 2507 fath- oms. The one exception is the Norwegian occurrence at 50 fathoms.
The single specimen from the eastern Pacific appears to differ from other described species and is designated:
Fissurisepta pacifica CowAN, spec. nov.
Description of Holotype: Shell delicate, white with very thin straw coloured surface pigmentation, conical, with anterior slope slightly convex, and posterior slope slightly concave; foramen somewhat damaged but apparently al- most circular and situated slightly behind centre. Sculpture of small pustules widely spaced, nowhere closer to each other than 4 or 5 times their diameters (Figure 3) ; ar- ranged generally in horizontal rows around the shell, about 6 rows in the height of the shell. On the sides, pus- tules of adjacent rows arranged so that some diagonal order is apparent, sloping upward toward the anterior end. Interior of shell glossy white, septum thin, straight, transverse, extending obliquely downward at an angle of 20° from the anterior slope for about half the height of the shell; free margin semilunate. Dimensions of shell: length 5.1mm; width 3.85 mm; height 2.6mm. Subse- quent to the preparation of this description the specimen was broken in transit. The fragments remaining reveal details of surface sculpture but not overall shape, the fora- men nor the septum.
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The soft parts of the genus have not previously been described.
The soft parts of the posterior segment of the body of our specimen are badly damaged but the portions avail- able for study include the head and the mantle cavity anterior to the heart. Figure 1 illustrates the general features of the head. From the ventral aspect the oral disk is wider than long. There are two pairs of cephalic tentacles, and in the preserved state the anterior pair is thick, blunt and turned down alongside the oral disk. The posterior pair is long and slender. There are no eyes.
The most remarkable feature of the superficial anato- my is that of the ctenidia. Cox (1964, p. 194) states that all Recent species belonging to the suborder Pleurotomari- ina, with the single exception of the right ctenidium of Scissurellidae, have bipectinate ctenidia. Our specimen
Figure 1
Fissurisepta pacifica Cowan, spec. nov. Ventro-lateral view of head end.
has disproportionately large gills that occupy almost the entire anterior mantle chamber and both gills are mono- pectinate (Figure 2). The main axis of each ctenidium is external and it, as well as most of the length of each branchial filament, is fused with or adherent to the mantle. The posterior filaments are free for their terminal thirds. This is thus the only Pleurotomariine known to have symmetrically monopectinate ctenidia. Other distinctive anatomical features should be sought in any fresh speci- mens that become available.
Type Material: A single known specimen number 6522, Cowan Collection, University of British Columbia, will be
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Figure 2 Fissurisepta pacifica Cowan, spec. nov. Dorsal view of anterior third, showing ctenidia as seen through transparent mantle.
deposited in the type collection of the National Museum of Canada as N. M. C. Number 45744. Type Locality: West north west of Triangle Island, Brit- ish Columbia, 51°09’ N Latitude, 130°09’ W Longitude, haul number 63-214 of the Fisheries Research Board of Canada, Cowan station 863; 470 - 480 fathoms. Collected by D. B. Quayle, September 11, 1964. Discussion: Fissurisepta pacifica is generally similar in shell details to EF soyoae Kuropa as described and figured by him in 1951. It differs, however, in being relatively flatter, with the height about two thirds of the width rather than equal to it. It differs also in the number and arrangement of the tubercles on the shell, which in F soyoae are shown to be numerous and in well organized rows of closely placed studs arranged obliquely, whereas in FE pacifica they are widely separated, few in number and in generally horizontal rows.
This must be a scarce species as just one specimen has been taken at about 30 stations below 200 fathoms worked by us in the past 3 years.
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An examination of descriptions of other species hither- to assigned to this subgenus suggests that some detailed re- examination is necessary. The type species Fissurisepta papillosa SEGUENZA is known only as a fossil but our species subscribes to the shell details as does EF soyoae. Puncturella (Fissurisepta) Wooprinc, 1928 differs in such essential details of shell structure as thickness, height, external sculpture and in the size of the shelf. It may well be improperly assigned to Fissurisepta.
The unique features of the ctenidia of Fissurisepta pa- cifica lead me to conclude that a separate generic desig- nation is necessary to recognize the degree of departure from the characteristics of representatives of Puncturella. Accordingly, on the assumption that the other species at- tributed to the subgenus Fissurisepta possess or possessed the same ctenidial structure, I suggest that Fissurisepta be accorded generic rank.
Figure 3
Fissurisepta pacifica Cowan, spec. nov. Surface detail of holotype.
The definition of the genus Fissurisepta can be stated: Prosobranch, Zeugobranch gastropods of small size with tall-conical shells in which the aperture is apical. The septum large, about half the height of the shell and pas- sing straight from side to side. External sculpture of the shell variable, consisting of either delicate vertical striae or of minute, widely separated studs in horizontal or oblique rows.
Animal with 2 pairs of cephalic tentacles, the posterior long and slender, no eyes, ctenidia paired, symmetrical and monopectinate, attached for most of their length to the inner surface of the mantle.
All but one of the living and fossil forms described have been taken from the northern oceans. There is, how- ever, a New Zealand Fissurellid, Puncturella manawata- whia Powe Lt, that, from published descriptions seems
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closely similar. It would be interesting to study this species in more detail.
ACKNOWLEDGMENTS
Dr.James H. McLean, Los Angeles County Museum of Natural History assisted with the preliminary identifica- tion and provided the photographic figures; the anatom- ical figures are the work of Margaret Jensen.
LITERATURE CITED
CrarkE, ArTHUR H., Jr.
1961. Abyssal mollusks from the South Atlantic Ocean.
Bull. Mus. Comp. Zool., Harvard, 125 (12): 345 - 387; 4 plts. Cox, Lestie REGINALD
1960. | Gastropoda/General characteristics of Gastropoda In: R.C. Moore, Treatise on invertebrate paleontology Prt. I, vol. 1: 84 - 169; figs. 51 - 88E
Dati, WiLL1AM HEALEY
1889. Reports on the results of dredging, . . . in the Gulf of Mexico (1877-78) and in the Caribbean Sea (1879-80), by the U. S. Coast Survey Steamer “Blake”, . . . Report on the Mollusca, pt. 2, Gastropoda and Scaphopoda. Bull. Mus. Comp. Zool. 18 (2) : 1 - 492; plts. 1 - 40
1927. Small shells from dredgings off the southeast coast of the United States by the United States Fisheries Steamer “Albatross” in 1885 and 1886. Proc. U. S. Nat. Mus. 70: 1- 134
DAUTZENBERG, PHILIPPE & HENRI FISCHER
1927. Résultats comparat. scientif: accomplies sur son yacht par
Albert 1** de Monaco. 77: 224; plt. 7, fig. 16 FaRFANTE, ISABEL PEREZ
1947. The genera Zeidora, Nesta, Emarginula, Rimula, and Puncturella in the Western Atlantic. Johnsonia 2 (24): 93 - 148
JEFFREYS, JOHN Gwyn
1882. On Mollusca procured during the “Lightning” and “Porcupine” expeditions, 1867-70 (Part V). Proc. Zool. Soc. London for 1882: 656 - 687; 2 plts.
Kuropa, ToKuUBEI
1951. _— Illustrated catalogue of Japanese shells. No. 17: Fissur-
ellidae, p. 116 OKUTANI, TAKASHI
1964. | Report on the archibenthal and abyssal gastropod Mol- lusca mainly collected from Sagami Bay and adjacent waters by the R. V. Soyo-Maru during the years 1955 - 1963. Journ. Fac. Sci., Univ. Tokyo, Sec. II, 15 (3): 371 - 447
PowELL, ARTHUR WILLIAM BADEN
1937. | New species of marine mollusca from New Zealand.
Discovery Reprts. 15: 153 - 222; 11 plts. SEGUENZzA, G.
1863. Paleontologia malacologia dei terreni Terziarii del dis- tretto dei Messina ... Fanuglia Fissurellidi. Amali Accad. Aspir. Naturalisti, Naples, ser. 3, 2: 83 - 86
Wooprinc, WENDELL PHILLIPS
1928. Miocene mollusks from Bowden, Jamaica. Part 2: Gas- tropods and discussion of results. Carnegie Inst. Washington, Publ. 385: i- vii + 1-564; 3 text figs.; plts. 1-40 (28 Nov.)
peng
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Seasonal Gonadal Changes of Adult Oviparous Oysters
in Tomales Bay, California
BY
CARL J. BERG, Jr.
Pacific Marine Station, Dillon Beach, California ':?
(Plates 1 to 3; 1 Text figure)
INTRODUCTION
Two SPECIES OF oviparous oysters, Crassostrea virginica (GmetIn, 1791), the Eastern oyster, and Crassostrea gigas (THUNBERG, 1793), the Japanese oyster, were intro- duced into Tomales Bay, California for commercial pur- poses. Because these oysters do not reproduce in its waters, shipments of adult oysters or oyster spat must be period- ically transplanted into this bay. It is the purpose of this study to compare the seasonal gonadal changes which occur in the two species of adult oysters in Tomales Bay with one another, and to compare them with similar changes occurring in the same species of oysters in other regions. The differences in gonadal changes will be related to variations in environmental conditions and to specific or racial characteristics.
Tomales Bay is located on the Northern Californian Coast, approximately 40 miles north of San Francisco. The oysters used in this study were kept at Tomales Bay Oyster Company, which is situated in the cove between Millerton and North Double Point, near the headwaters of the bay. This area has long been the site of oyster culture. The native or Olympia oyster (Ostrea lurida CarPENTER, 1864) was the first oyster species grown in Tomales Bay to be shipped to the markets of San Fran- cisco. However, upon completion of the transcontinental Central Pacific Railroad in May 1869, it was possible for the first time to ship live adult Crassostrea virginica and its seed to the Pacific coast. In 1875, 17 carloads of C. virginica were laid out near Millerton Station in Tomales Bay (TownsEnp, 1893). Cultivation of C. virginica in Tomales Bay has continued intermittently since that time.
‘ Submitted in partial fulfilment of the requirements for the Degree of Master of Science in Marine Science at the University of the Pacific, Stockton, California.
2 Present address: Department of Zoology, University of Hawaii, Honolulu, Hawaii 96822
The tidelands of Tomales Bay Ovster Company were also the first areas in California to be used for the culture of Japanese oysters (C. gigas), which were introduced into Puget Sound in 1902, and later, in 1928, into Tomales Bay (BarreTT, 1963). Both C. virginica and C. gigas have failed to reproduce in Tomales Bay and continued impor- tation of adult oysters or seed has been necessary.
Because of their commercial value, there have been numerous attempts at the artificial introduction of oysters into areas lacking natural populations, or in which the native oyster is of little economic importance. The oysters of the genus Crassostrea Sacco, 1897, are more often used as introduced species than are those of the genus Ostrea LINNAEUS, 1758, since they have a greater ability to survive in extreme and varying environments. Cyrass- ostrea virginica has been introduced into the oyster beds of Britain, the Pacific Coast of North America, and the island of Oahu, Hawaii. Crassostrea gigas has likewise been introduced into the oyster beds of the Pacific Coast of North America; Oahu, Hawaii; also into Melbourne Harbour, Australia; Mobile Bay, Alabama; and Barnstable Bay, Massachusetts. The Portuguese oyster, C’. angulata (Lamarck, 1819) has taken over all of the French oyster beds and now also lives, but does not reproduce, in British beds. One noteworthy and successful introduction of oysters of the genus Ostrea took place in the waters of Boothbay Harbor, Maine, where LoosANorF (1955) had transplanted European oysters (Ostrea edulis LINNAEUS, 1758) in 1949.
In many of the attempts to introduce a specics of oyster to a new location, the animals may have survived and grown well, but failed to reproduce. To determine the reason for the failure of the species to reproduce, one must be familiar with the seasonal gonadal changes which occur in the oysters in their native environment. There have been studies on gonadal changes in each of the commercially valuable species of oysters. Crassostrea
Page 28
virginica is the most extensively studied species of the oviparous oysters (Hopkins, 1931; Loosanorr, 1932, 1942, 1965; LoosaNorF & ENGLE, 1942; BuTLER, 1949; KENNEDY & BATTLE, 1964; SEVILLA & Monpracon, 1965). Crassostrea gigas has had little work done on its gametic activity (Imai et al., 1950; Imar & Sax1, 1961) and the same is true with the other oviparous oysters: C. commer- cialis (IREDALE & RouGHLEy, 1933) (RouGHLEy, 1933; Cieanp, 1947); C. angulata (BARcETON, 1942, 1943) ; and C. madrasensis (PRESTON) (ANOoNYMouS, 1950). Studies have also been made of gonadal changes in the larviparous oysters: Ostrea edulis (Orton, 1927, 1931, 1933; Core, 1942) and O. lurida (Cor, 1931, 1932).
Even less work has been done on the seasonal gonadal changes in oysters which have been introduced into new areas. LoosanoFF (1962a) gave a detailed description of the changes which occurred in the gonads of O. edulis introduced into Boothbay Harbor, and briefly mentioned the gonadal changes which occurred in C. gigas trans- planted into Milford Harbor (LoosanorF & Davis, 1963). Ga.tsorF (1929) and KaTKaNSky & SPARKS (1966) discussed the gonadal changes and sex ratios which oc- curred in C. gigas cultured in the waters of the State of Washington, and Evsey (1932, 1933, 1934) described the changes in C. gigas in the waters of British Columbia. Ostrea lurida is the only other species in which the sea- sonal gonadal changes have been thoroughly studied in both the native environment (Cog, 1931, 1932) and in the area to which it was introduced (Hort, 1933).
The introduction of oysters into a new environment is valuable for both scientific and commercial reasons. Al- though it has long been known that Crassostrea virginica and C’.. gigas do not reproduce in Tomales Bay, no one has ever done a detailed study of the reproductive cycle or the seasonal histological changes in the gonads. This study, therefore, extends the knowledge concerning an oyster’s adaptation to its new environment and may help to define the reasons for the failure of these two species of oysters to reproduce in Tomales Bay.
MATERIALS ann METHODS
The oysters used in this study were obtained from Long Island Sound and from Canadian waters through the courtesy of the Department of Fish and Game of the State of California, Dr. Victor L. Loosanoff and Dr. Ed- mund H. Smith of the Pacific Marine Station. Four hund- red and fifty 2-year old Crassostrea gigas of Canadian ori- gin were taken from the mud-flats at Tomales Bay Oyster Company where they had been raised. They were then placed in wire-mesh trays and suspended from racks at
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the Oyster Company on October 20, 1966. A similar number of 2-year old C. virginica was received on Octo- ber 26, 1966, and was placed in identical adjacent trays. Fifteen oysters of each species were collected at bi-weekly intervals for 15 months. An additional sample of 13 C. virginica was obtained on October 5, 1966, from a stock which had been previously kept at Tomales Bay Oyster Company.
The height (distance between the umbo and the ventral valve margin) and length (distance between anterior and posterior valve margins) of each oyster were measured with calipers before the oyster was opened. A tissue sample was taken from the gonadal area near the labial palps in conformity with the practice of the biological labora- tories of the United States Bureau of Commercial Fish- eries. This gonadal tissue was fixed in Bouin’s solution, infiltrated with 52.5° C paraffin, sectioned at 10 B, and stained with Heidenhain’s iron hematoxylin and aqueous eosin Y, using standard procedures. The tissues were then microscopically analysed for sex and state of gametogen- esis.
Hydrographic data were collected on each sampling date; they included measurements of salinity, hydrogen- ion concentration, and turbidity of water samples taken one foot above the bottom by means of a Frautschy-bottle sampling device. Sub-surface water temperatures were taken by suspending a thermometer over the bottom. Surface-water hydrographic data were obtained from rec- ords kept at the Pacific Marine Station.
Large bags of sun-bleached oyster shells were suspended near the trays of oysters for 2-week periods from May 4, 1967 until October 19, 1967. Fifty shells were chosen at random from each bag and examined for oyster spat. During the same period plankton tows were taken over the beds of Tomales Bay Oyster Company and examined for bivalve larvae. All oyster larvae were identified by length-width measurements after the method of Loosan- oFF, Davis & CHANLEY, 1966.
OBSERVATIONS
A detailed description of the sequence of events in the development of functional gametes has been given by LoosanoFF (1942) for Crassostrea virginica. Since the seasonal gonadal changes observed in both C. virginica and C. gigas in Tomales Bay differed little from those described, except with regard to timing (LoOOSANOFF & EncLE, 1940; Loosanorr, 1965), only a résumé of the gonadal changes will be given here. It is most convenient to describe the seasonal gonadal changes which occurred
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Salinity %,
Temperature in ° C
Co) ONDJFMAMJJAS ON D Month
Figure 1
Water temperature and salinity at Tomales Bay Oyster Company from October 1966 to December 1967
in the two species separately and in the order in which they were observed.
Specimens of Crassostrea virginica were obtained from Tomales Bay Oyster Company on October 5, 1966, where they had been kept for at least a year. The small gonadal
follicles of these oysters contained only indifferent sex cells and were scattered in the large masses of connective tissue. This “indifferent stage” (LoosanorrF, 1942, p. 203) was characteristic in the months of September, October, and November of 1967.
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The remaining samples of gonadal tissue were collected from Crassostrea virginica transplanted into Tomales Bay Oyster Company beds on October 26, 1966. Slight ga- metic activity ended the indifferent stage of some of the oysters during the months of November and December. Primary and secondary gametogonia started to develop along the follicular walls, making sex determination pos- sible. The follicles began to expand gradually.
A marked increase in the size of the follicles and in the acceleration of maturation of the gametes was no- ticed in late December and January. Ovocytes began to fill the follicles and spermatids were already devel- oping. The follicles showed rapid growth and ramification.
Continued maturation of the gametes took place in February and March, concurrently with the disappearance of the voluminous vesicular connective tissue. In some instances, mature ova and spermatozoa were present.
By the sixth of April, most of the gonads were packed with ripe gametes, some of which nearly filled the ciliated genital ducts (Plate 1, Figures 1 and 2). However, a few cells at the earlier stages of gametogenesis were pres- ent on the follicular walls. This state of maximum ripe- ness was maintained throughout the spring. Although a few oysters were partially spawned beginning at the
middle of April, mass spawning did not occur until the ©
middle of June and continued until the middle of July. On July 13, 87% of the sample was completely spawned. This coincided with the time of greatest rate of increase in water temperature (Text figure 1).
The gonads of spawned oysters were characterized by the absence of mature gametes and the shrunken appear- ance of the follicles (Plate 1, Figures 3 and 4). Great numbers of phagocytic cells were present, both inside the lumina of the follicles and around the outside walls. All unshed gametes are devoured by these cells. The lumina of the follicles were being closed by elongation and the shrinking of follicular tissue. Simultaneously, the cells of
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the vesicular connective tissue proliferated, filling all inter- follicular spaces. Resorption of gametes continued from the post-spawning stages in July until the first week of November, and a few follicles were observed to contain mature gametes being phagocytized as late as December. However, most gonads were in the indifferent stage by September.
All samples of gonadal tissue from Crassostrea gigas were collected from oysters which had been raised in Tomales Bay from the imported seed. Although the sea- sonal gonadal changes which were observed in C. gigas resembled those of C. virginica, there were differences between species in timing and in the homogeneity of the sample. The indifferent stage of gametogenesis was char- acteristic of the months of November and December.
The little gametic development and proliferation of the follicles which occurred in December and January is the only activity which might be characterised as the “sex- differentiation stage” (Loosanorr, 1942, p. 203).
Very rapid maturation of the gametes took place in January and February, with a great expansion of the follicles. March was the month of greatest maturation and proliferation. By the eleventh of March, ripe ova and spermatozoa were present in a few of the follicles.
From April 6 until July 27, 95% of all the gonads sampled were filled with ripe gametes (Plate 2, Figures 5 and 6). They retained gametes throughout the spring, however, because no spawning took place until after the twenty-seventh of July. Between the dates of July 27 and August 10, mass spawning of Crassostrea gigas occurred. This coincided with the warmest water temperatures to that date (Text figure 1). Again, the follicles of the spawned gonads were shrunken and devoid of ripe gam- etes (Plate 2, Figures 7 and 8).
Resorption and cytolysis of the unshed gametes started immediately after spawning was completed and con-
Explanation of Plate 1
Figure 1: Section of gonad of ripe female Crassostrea virginica collected April 6, 1967 (X 125)
Figure 2: Section of gonad of ripe male Crassostrea virginica collected April 6, 1967 (X 125)
Figure 3: Section of gonad of spawned female Crassostrea virginica collected July 13, 1967 (X 125)
Figure 4: Section of gonad of spawned male Crassostrea virginica collected July 13, 1967 (X 125)
Explanation of Plate 2
Figure 5: Section of gonad of ripe female Crassostrea gigas collected April 6, 1967 (X 125)
Figure 6: Section of gonad of ripe male Crassostrea gigas collected April 6, 1967 (X 125)
Figure 7: Section of gonad of spawned female Crassostrea gigas
with a few ova remaining in gonad tubules.
collected August 10, 1967 (X 125) Figure 8: Section of gonad of spawned male Crassostrea gigas showing spermatozoa remaining in gonad tubules.
collected August 10, 1967 (X 125)
[BERG] Plate 1
Tue VELIGER, Vol. 12, No. 1
| ' } i t é ah U SA ¢ i a 4 i n Ara = Cat re i 4 i i , a v 7 4 ° - Cah
Tue VELIGER, Vol. 12, No. 1 [Berc] Plate 2
ee mY baal j » Y Ad me a ~ Se ee Figure 5
Fy , ¥ eo 2 ‘ es, «* tet oe | 7 y , ms Rey : s ke . 2 5 4 , «4 , 2 ; ; 3 » » ty ‘ ; .* ; , : > . : ¥
Figure 8
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tinued until December. Many spermatozoa and ova were found being phagocytized, some until late December.
In addition to observing the gonadal changes, the sex ratio was also noted. Frequently, however, the sex could not be determined since the gametes were not yet differ- entiated. In a sample of 387 Crassostrea virginica, 139 were male, 114 were female, and 132 were undifferenti- ated. Two morphological hermaphrodites were found. Both contained follicles packed with spermatozoa and a few cytolized ova (Plate 3, Figure 9). In a sample of 382 C. gigas 100 were male, 194 were female, and 87 were undifferentiated. Only one hermaphrodite was found for this species. Unlike those observed in the sample of C. virginica, the follicles of the hermaphroditic C. gigas con- tained both male and female gametes in various stages of development (Plate 3, Figure 10).
The hydrographic conditions observed in the bay are presented in graphic form (Text figure 1). The range of hydrogen-ion concentration was not great enough (7.70 to 8.16) to affect gonadal changes, neither did it exhibit seasonal variances. Hence, these data are not presented in this article. The turbidity determinations are not presented either, although the turbidity of the water showed distinct seasonal variations. Both temperature and salinity may affect gametogenesis (KINNE, 1963, 1964; LoosaNnorr, 1945, 1948). Text figure 1 presents temperature and sa- linity data in graphic form so that seasonal irends may be more apparent.
The difference between surface and bottom salinity samples is significant and noteworthy since the oysters were exposed to surface water at low tides. The extreme range in salinities is due to the effect of fresh-water runoff during the winter and spring, and to evaporation during the summer. Salinities in excess of 32%, prevailed from July to December. Throughout the winter and spring, however, the salinity remained around 25%.
The water temperature at the oyster beds exhibited similar seasonal fluctuations. A trend of rising tempera- tures starts in January after a brief cold period and con- tinues until June. The water temperature remains close to 20°C during June, July, August and September. The water then begins to cool to its lowest temperature at the end of the year. Rarely did the temperature remain below 10°C for more than a few days, neither did it range much above 20° C. All hydrographic observations, including temperature determinations, were made at approximately mid-tide. More extreme temperatures may exist during slack tides, but thermograph records for that area showed that the water temperatures remain markedly constant throughout the tidal cycle.
Finally, few Crassostrea larvae were collected by the plankton tows and few spat were found on shells. Some
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straight-hinge stage larvae were found in the plankton samples of August 24 which had general appearances and dimensions similar to those reported for C. virginica and C. gigas (LoosanorF, Davis & CHANLEY, 1966). Although bivalve larvae were collected in every sample, no others approximated the proper size or shape.
A total of 6 oyster spat was found set on shells; one on July 13, and 5 on August 10. Three of those found on August 10 had settled on the inside of the right valve of an oyster which was gaping. The inside of the shell was free of mud, although the outside was covered. Through-
out the summer, all shells in the wire-mesh bags were
found to be covered with mud after 2 weeks in the water.
It is surprising that any larvae were able to set on such shells.
DISCUSSION
Gametogenesis and spawning of oysters are directly cor- related to water temperatures. LoosanorF & Davis in 1952 have shown the temperature and time requirements to condition Crassostrea virginica to spawn. Their experi- ments showed that 10° C was not high enough to induce gametic activitics. However, they report ripening and spawning for oysters when the temperature had reached only 15°C. Later experiments (Loosanorr, 1958, 1969) proved that maturation of gametes was possible after 68 days of conditioning at 12° C. The water temperatures at Tomales Bay Oyster Company remained above 12°C throughout the year, except for short periods of time in December and January. During the summer, the water temperature was not as high as those reported for either Long Island Sound or the Miyagi Prefecture, Japan, from where the oysters originally came. The differences in seasonal temperature fluctuations between Tomales Bay and the native environments of the oysters were respon- sible for the variances in gonadal changes (Table 1). Low salinities which may have an influence on gonad development (LoosanorFr, 1948; 1952), were not en- countered for extended periods of time, thus they did not seem to affect gonadal changes in oysters in Tomales Bay. A comparison of seasonal gonadal changes between Crassostrea virginica and C. gigas must take into account differences between the species and racial variations within each species. As mentioned previously, the seasonal gonadal changes observed in both C. virginica and C. gigas differed little from each other, except for timing. The differences in timing are clearly portrayed in Table 1. The only time of agreement in stages of gametogenesis was from the first week in April, when approximately 757% of the samples from both species contained ripe ova and
Page 32
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Table 1
Periods of Basic Gonadal Stages in Crassostrea virginica and Crassostrea gigas in Different Geographic Areas.
Crassostrea virginica
Stage Tomales Bay Long Island California Sound
Spring January
Development and and February May
Crassostrea gigas
Tomales Bay State of Miyagi Prefecture, California Washington Japan February May
and — March June
First April June April May May Ripening ‘
Spawning through August From Post- From Post- Resorption Spawning to Spawning to October October Undiffer- September August entiated through and November September Fall November October Gametogenesis and and
December November
December Inactive None to April
sperm, until the end of June when most of C. virginica had spawned. During this period, no C. gigas spawned, but a few of C’. virginica had partially spawned and some were undergoing resorption. Mass spawning of C. virgini- ca was completed at least two weeks before C. gigas spawned, and it extended over a greater period of time than did the 2-week mass spawning of C. gigas. Since the shed gametes of both species can induce spawning in the males of either species (GaLTSoFF, 1964), it is sur- prising that C. gigas did not spawn simultaneously with C. virginica. A combination of thermal and chemical re- quirements is often needed to induce spawning. These requirements were obviously not met for C. gigas until a later date.
Not all of the oysters of either species had spawned completely. More of Crassostrea gigas contained ripe ova and spermatozoa, and retained them until later dates, than did C. virginica. Resorption of unshed gametes con- tinued into December for C’. gigas. During and following resorption, the gonadal follicles were in the undifferenti- ated stage. This stage was halted with the advent of gametogenesis. In C. virginica, gametogenesis started in November, one month earlier than in C. gigas. Matura- tion proceeded gradually until after the first of the year for both species. In late December, January, and February,
July July August and and and August September
From Post- Spawning to — December
From Post- Spawning to December
October through
November and December
December
February through April
the gametes of C. virginica showed a great acceleration in maturation. This acceleration, termed “spring develop- ment” by LoosanorF (1942, p. 198), again occurred one month earlier in C. virginica than in C. gigas. However, C. gigas showed a greater burst of gametic activity in March. Thus, both species reached sexual maturity at the same time. In general, C. gigas has a higher temperature requirement for the initiation of both gametogenesis and spawning. This is evident by the slower development and later spawning dates. Moreover, unshed gametes are re- tained by C. gigas for longer periods of time before being resorbed. Similar differences were observed between C. virginica and C. gigas transplanted into Milford Harbor (LoosanorF & Davis, 1963).
A series of observations on seasonal gonadal changes of two other bivalve species was conducted concurrently with this study (LEonarD, 1969). Ostrea edulis, trans- planted into Tomales Bay Oyster Company beds, and Pododesmus cepio (Gray, 1850), the native rock jingle, both showed gonadal changes at dates which correspond well with those observed for Crassostrea virginica and C. gigas and with the seasonal fluctuations in temperature.
A comparison of the timing of the gonadal changes of Crassostrea virginica in Tomales Bay with those reported for it in Long Island Sound (Loosanorr, 1942; 1965)
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emphasizes tiie effect of temperature upon gametogen- esis and spawning (Table 1). Spawning occurred in both locations at the end of June when the water temperature was about 20° C. Post-spawning resorption continues into October in both locations, but the undifferentiated stage is being completed in Long Island Sound in September, and not until November in Tomales Bay.
Fall gametogenesis extends from October to December in Long Island Sound but occurs one month later in Tomales Bay. Whereas Long Island Sound oysters exhibit no gametic activity from December until April or May, oysters in Tomales Bay proceeded to carry out gameto- genesis through the winter, with the period of fastest ma- turation occurring in February. In April, when oysters in Tomales Bay were already ripe, Long Island Sound oysters were developing only primary and secondary gametocytes. During the entire spring, oysters in Tomales Bay contain ripe gametes, while the gametes in Long Island Sound oysters are just maturing. In both areas, the gametes are ripe in June.
To reiterate, the major difference in gonadal changes between Crassostrea virginica in Long Island Sound and those transplanted into Tomales Bay is that the follicles of the latter do not exhibit an inactive stage; rather they continue to develop from November until they are mature in April. The ripe gametes then remain in the follicles until spawning occurs. This is probably due to differences in winter temperatures of the two areas.
There is little information on the seasonal gonadal changes of Crassostrea gigas. Although a few authors mention the temperature at which spawning occurred, none describe the histological changes taking place in the gonads prior to spawning. Spawning is recorded for temperatures below 20°C (Fuyrra, 1929; Hopxins, 1936; ScHarFEeR, 1938; CuHapMaN & EsvetpT, 1943), which is well within the range encountered in Tomales Bay. Imar & Saki (1961) report that spawning takes place in Miyagi strains of C. gigas late in August and early in September, although the gonads were ripe as early as May. Amemiya (1928), however, reports that spawning of northern province Japanese oysters may take place in May and June. The timing of gametogenesis and spawning of C. gigas in Tomales Bay best corresponds with the data from Imari & SAKI (op. cit.) but seems to be one month ahead at all stages.
Crassostrea gigas raised in the State of Washington also exhibit gonadal changes and spawning at tempera- tures almost identical with those observed in Tomales Bay. Spawning is reported to occur during the last part of July and the first part of August when the water tempera- tures ranged between 18° C and 20°C (Scuaerer, 1938; CHAPMAN & EsveLpT, 1943). This coincides perfectly
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with the observations of spawning in Tomales Bay. In the follicles of C. gigas in Washington waters, resorption of the unshed gametes continues through December (Ga.tsorF, 1929). The follicles begin to proliferate in December and January (KaTansky & Sparks, 1966), but then gametic activity appears to be arrested. Re- sumption of maturation of the gametes takes place in April or May, with ripe ova and active sperm again present by May (GaLTsorr, op. cit.; CHAPMAN & Es- VELDT, op. cit.). The inactive wintering stage is similar to that of C. virginica in Long Island Sound. As mentioned previously, C. gigas in Tomales Bay does not become in- active; rather the gametes mature most during the months of January, February, and March.
It is apparent that Crassostrea gigas in Tomales Bay meets with seasonal temperature fluctuations which are similar to those in the State of Washington, where they were first introduced. Normal gametogenesis and spawn- ing occurs in all three areas. Only in Japan, however, is the combination of all environmental factors consistently suitable for the setting of oyster larvae. Some setting of commercial value also occurs occasionally in Washington and Canadian waters. In fact, the oysters used in this study were from Canadian seed. There have been no reports of a large set of either C. gigas or C. virginica in Tomales Bay, although one naturally set C. gigas was found. Factors other than temperature, salinity, and hy- drogen-ion concentration are probably involved, since these factors correspond well with those found in the oyster’s native environment. Excessive turbidities were noticed throughout the summer. These probably had a deleterious effect upon both the larvae and the places available for setting. A more complete discussion of the effect of the environment upon the larvae will be pre- sented at a later date.
LoosaNnoFF (1962b) has shown the effect of turbidity upon oyster larvae, and LoosANoFF & ToMMERS (1948) have suggested that there exist races of C. virginica which exhibit different abilities to survive high turbidi- ties. Furthermore, races based upon the oysters’ adapt- abilities to an environment, shell characters, and temper- ature requirements for breeding have been described for both C. virginica and C. gigas (STauBER, 1950; LoosANOFF & NoMEjKo, 1951; Imar & Saxt, 1961; Loosanorr, 1969). Oysters from northern latitudes have been shown by these authors to have a much lower temperature requirement for the development of gametes and the induction of spawning. The results of this study showed great differ- ences within the population of C. virginica dredged from Long Island Sound and transplanted into Tomales Bay. In any one sample, the oyster gonads would show a continuum through two or three stages of development.
Page 34
Some oysters ripened and spawned much earlier than most; others much later. In addition, resorption of unshed gametes proceeded at greatly varying rates. Some oysters contained ripe ova and spermatozoa even in December. The population of C. gigas did not show as great variance, probably because the oysters were collected as seed from a small area and then transplanted into Tomales Bay. The greater homogeneity of the population indicates that only one race was observed. Some individual differences were noted, but this should be expected. ‘The oysters used in this study came from the northern limits of the distri- bution of each species. If more southern oysters were used, the environmental conditions in Tomales Bay would not have favored spawning. In all attempts at intro- ducing a species into a new area, consideration must be given to the racial characteristics of the oysters. Animals with the lowest temperature requirements are best suited for such experiments.
Recent findings support the earlier observations that crowded conditions of oysters might favor the develop- ment of one sex or the other. In crowded conditions, Crassostrea virginica are reported to show a population trend toward the male phase (BuRKENROAD, 1931; NEED- LER, 1934) and C’. gigas to the female phase (KATANSKY & SPARKS, 1966). However, experimental evidence (V. L. LoosanorF, MS) has shown that crowded conditions did not affect sex determination in adult C. virginica. The samples taken for this study indicate that a female phase may be favored by C. gigas in crowded conditions, but that C. virginica showed approximately equal sex ratios.
The number of hermaphrodites found is also within the normal range. (Gattsorr, 1964). In Crassostrea gigas 0.26% were hermaphrodites (1 out of 382) and in C. virginica 0.52% (2 out of 387). The few ova present in the ripe male follicles of C. virginica were cytolized (Plate 3, Figure 9), but both the ova and the spermatozoa in C. gigas appeared normal (Plate 3, Figure 10), with primary and secondary spermatocytes present. Therefore, the hermaphrodites observed in C.. virginica would best be called morphological, but the one C. gigas was probably a functional hermaphrodite. All of the hermaphrodites were collected in the spring during the period of greatest gametic activity. It is unlikely, therefore, that the gametes had been carried over from the previous season.
A few major conclusions have been drawn from this study of the seasonal gonadal changes in Crassostrea
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virginica and C’. gigas introduced into Tomales Bay, Cali- fornia. Differences in the gonadal changes between in- dividuals of each species, between two species, and between the oysters in Tomales Bay and those of the same species in their native environment are attributed to individual, racial, specific, and environmental variations. The sample of C. gigas was racially more homogeneous than that of C. virginica, and it required warmer temper- atures to initiate gametogenesis and spawning. During the annual cycle, one continuous period of gametic activity took place in both species. There was no inactive stage as is usually found in most species of Crassostrea in their native environments, because the water temperatures at Tomales Bay Oyster Company were favorable enough throughout the year to encourage gametogenesis and growth. The inability of the two species to propagate in Tomales Bay is not due to a failure to spawn, but rather to a failure of the larvae to reach the settled spat stage.
ACKNOWLEDGMENTS
I wish to thank Dr. Victor L. Loosanoff for the invaluable guidance and encouragement he gave me throughout the course of this study. My thanks are also extended to Dr. Edmund H. Smith, Dr. John S. Tucker, and Dr. Walter Narchi for their helpful advice and assistance.
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Explanation of Plate 3
Figure g: Section of gonad of a hermaphroditic Crassostrea vir- ginica containing both spermatozoa and cytolized ova. collected May 18, 1967 (X 125)
Figure 10: Section of gonad of a hermaphroditic Crassostrea gigas containing both spermatozoa and ova collected April 6, 1967 (X 125)
TuHeE VELIcER, Vol. 12, No. 1 [Bers] Plate 3
Figure 10
i a we = _ i" ae 7, UP an : 7 i = = , < > 4+ - ‘ t a ¥ * _ i = = = i = f
2, / J : ~ 7 :
Vol. 12; No. 1
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Orton, JoHn H.
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1933. | Observations and experiments on sex change in the European oyster (Ostrea edulis). Part III. On the fate of the unspawned ova. Part IV. On the change from male to
female. Journ. Mar. Biol. Assoc. 19 (1): 1 - 53; 8 text figs. 22 tables Orton, Joun H. & C. AMIRTHALINGAM 1931. | Observations and experiments on sex-change in the Eu-
ropean oyster (O. edulis). Part II. On the gonad of egg- spawning individuals. Journ. Mar. Biol. Assoc. 17 (2): 315 - 324; 12 text figs.; 1 table Rovucu Ley, T. C. 1933. The life history of the Australian oyster Ostrea com- mercialis, Proc. Linn. Soc. N.S. W. 58 (3/4): 279 - 333; 18 plts.; 2 text figs. ScHaErer, MILNER B. 1938. Preliminary observations on the reproduction of the Japanese common oyster Ostrea gigas in Quilcene Bay, Wash- ington. Biol. Reprt.: Wash. State Dept. Fish. 36E: 1 - 36
Sevitta, Maria Luisa H. & EvA Monpracon C. 1965. Desarollo gonadico de Crassostrea virginica GMELIN en
la Laguna Tamiahua. 1: 51-69 SrauBer, LESLIE A.
Anales Inst. Nat. Invest. Biol. Pesc.
1950. The problem of physiological species with special ref-
erence to oysters and oyster drills.
2 text figs.; 1 table TOwNSEND, CHar.es H.
Ecology 31(1): 109- 118
1893. Report of observations respecting the oyster resources and oyster fishery of the Pacific Coast of the United States. Reprt. Comm. U.S.Comm. Fish and Fish. 1889-1891. 17:
343 - 372; plts. 2-11; 8 tables
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Levels
of Spontaneous Electrical and Acetylcholinesterase Activities
During Aestivation of the Indian Apple Snail, Pila globosa
BY
P MURALI MOHAN
AND
P MURALI KRISHNA DASS
Department of Zoology, S. V. University College, Tirupati (A.P.), India
(1 Text figure)
INTRODUCTION
Tue INDIAN APPLE SNAIL, Pila globosa (SwaInson, 1822) aestivates under drought conditions by retiring into the deeper layers of the mud and sealing itself with the oper- culum (PrasHap, 1925; Saxena, 1956). The general me- tabolism of the animal decreases to a low level during aestivation (MEENAKSHI, 1956; RAaGHUPATIRAMIREDDY, 1965). Under these conditions, it is likely that the nervous activity could also be low, since the necessity to respond to external environment does not arise. Moreover, the altered metabolism in aestivating snails may require a corresponding altered neuro-regulatory mechanism. Since the existence of such a mechanism is not known, an at- tempt was made to study these aspects, taking nervous activity as well as acetylcholinesterase activity as an index in aestivated animals.
MATERIALS anp METHODS
Active snails, Pila globosa, were made to aestivate for one month by embedding them in dry sand in wooden boxes (Saxena, 1956).
The normal and aestivated Pila were dissected, expo- sing the different nerve cords under the binocular micro- scope. The spontaneous electrical activity was recorded by chlorided silver electrodes. The potentials were fed into the Tektronix 502A dual beam oscilloscope through Grass p9 preamplifiers. The photographic recordings were made using a Grass Kymograph camera.
For the estimation of acetylcholinesterase activity, the nervous tissue including all ganglia and cords, of normal and aestivated Pila was isolated and washed repeatedly with gastropod Ringer solution (HucHES & KERKUT, 1956). The nervous tissue of each animal was used for a single analysis. The acetylcholinesterase (AChE) activ- ity was estimated following the modified method of MetTca tr as suggested by Murat KrisHna Dass (1968). The incubation mixture contained 0.1 ml of 5% homo- genate of the nervous tissue in 0.25M sucrose, and 1 ml of buffer-substrate mixture. After 4 an hour of incubation, the unreacted acetylcholine was determined by measuring the optical density at 540 my using Ultraviolet Spectro- photometer (Hilger and Watts, England), employing glass cuvettes of 10 mm light path.
RESULTS anp DISCUSSION
The level of spontaneous electrical activity has shown a definite decrease in all the nerves of the aestivated Pila from that of the normal as is evident from the recordings (Figure 1). Both the amplitude and frequency of the responses were affected on aestivation. A lower level of spontaneous activity parallels the lowered level of the active state of the animal (K.P. Rao, 1964; VeNxKaTa- cHari, 1968). Hence during aestivation, while the animal remains in a state of torpor, a decreased level of spon- taneous activity is expected. Similar decrease in electrical activity was observed in the brain and ganglia of pupae of diapausing insects (TySHTCHENKO & MANDELSTAM, 1965; Kutyna & TomBes, 1966).
40onV
| 0.4. sec
Figure 1
Spontaneous activity recorded from cerebral commissure (a1, a2),
supra-intestinal nerve (b 1, b2) and left pleuro-visceral connective
(c 1, c2) in normal (a1, b1, c1) and aestivated (a2, b2, c 2) Pila globosa
Note the decrease in the spike amplitude and frequency of pulses on aestivation
A direct relationship between electrical activity and AChE activity was demonstrated in relation to the behav- ior of scorpion (VENKATACHARI & Murat KrisHNA Dass, 1968). Since in the present case a considerable decrease in the spontaneous activity was observed, it is possible that the associated AChE activity might also have a corresponding decrease in activity. As is evident from ‘Table 1, there is a decrease in the AChE activity level
Table 1
Levels of acetylcholinesterase enzyme activity in normal and aestivating Pila globosa. (Activity is expressed in mg of acetylcholine metabolised per gm weight of tissue
per hour). Normal snails Aestivating snails % decrease during aestivation 338 + 20.09 281.33 + 17.78 16.76 (P > 0.001)
Each value in this table is an average of six separate analyses (six animals).-
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in nervous tissue of aestivated snails. This observation may possibly reiterate the direct relationship between elect- rical activity and AChE activity.
Since the nervous system in general is known to regulate the activities of the animal, the lowered nervous activity of aestivating snails in terms of decreased spontaneous and acetylcholinesterase activities could be responsible for their observed lowered metabolism. Further work along these lines is in progress.
SUMMARY
1. The spontaneous electrical and acetylcholinesterase ac- tivities were studied in the nervous tissue of normal and aestivated Pila globosa.
2. The spontaneous activity decreased in aestivated snails. Correspondingly, there was a decrease in the AChE activity.
ACKNOWLEDGMENTS
The authors wish to express their thanks to Dr. K.S. Babu and Dr. K.S. Swami of this Department for their kind help and valuable suggestions.
LITERATURE CITED
Hucues, G. M. « G. A. KerKutT
1956. Electrical activity in a slug ganglion in relation to the concentration of Locke solution. Journ. Exp. Biol. 33: 282 - 294
Kutyna, FE A. « A. S. ToMBEs
1966. — Bioelectric activity of the central nervous system in nor-
mal and diapausing alfalfa weevils. Nature 212: 956 - 957 MEENAKsSHI, V. R.
1956. Studies on physiology of Pila virens (LAMARCK) with special reference to aestivation. Ph. D. thesis, Annamalai University, India
Mura. KrisHna Dass, P. 1968. A modified method of Metcalf for AChE assay in
nervous and muscular tissues of different animals. | Unpubl. NacHMANSOBN, D. 1953. | Metabolism and function of the nerve cell. Harvey
Lectures 44: 57 - 99 Prasuap, B. 1925. Anatomy of the Indian apple snail Pila globosa. Mem. Ind. Mus. 8: 91 - 153 RAGHUPATIRAMIREDDY, S. 1965. The charge properties and metabolism of animals ex- posed to changed environments. Ph. D. thesis, Sri Venka- teswara University, India
Vol. 12; No. 1
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Pampapati, Rao K.
1964. | Neurophysiological studies on an arachnid scorpion, Heterometrus fulvipes. Journ. Anim. Morphol. Physiol. 11; 133 - 142
Saxena, B. B.
1956. | Some observations on the ecology and behaviour of the common Indian apple snail, Pila globosa (Swainson). Journ. Bombay Nat. Hist. Soc. 53: 733 - 736
TYSHTCHENKO, V. P & J. E. MANDELSTAM
1965. A study of spontaneous electrical activity and localiza- tion of cholinesterase in the nerve ganglia of Antheraea pernyi Guer at different stages of metamorphosis in pupal diapause. Journ. Insect. Physiol. 11: 1233 - 1239
VENKATACHARI, S, A. T.
1968. Electrical activity of the ventral nerve cord of scorpion.
Ph. D. thesis, Sri Venkateswara University, India. VENKATACHARI, S, A. T. & P Murai KrisHNA Dass
1968. Cholinesterase activity rhythm in the ventral nerve corc
of scorpion. Life Sciences 7: 617 - 621
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Macoma (Psammacoma) pulleyi, a New Clam from Louisiana
BY
PAUL S. BOYER
Department of Geology, Rice University, Houston, Texas ‘77001
(2 Text figures)
THE FOLLOWING PELECYPOD was dredged by the author in the course of investigations of invertebrate ecology off the coast of Louisiana. Reference to published descrip- tions and comparison with the collections in the U.S. National Museum indicate that this clam is a new species.
PELECYPODA
TELLINIDAE
Macoma Leacu, 1819
(Psammacoma) Dati 1900
Macoma (Psammacoma) pulleyi Boyer, spec. nov. (Figure 1)
Description: Shell thin, white, moderately inflated, elon- gate, inequilateral, equivalve, and covered by a very thin, brown periostracum. Anterior end longer, the anterior dorsal margin almost rectilinear, the anterior margin rounded above and more gently and evenly curved below. Ventral margin nearly straight, subparallel to the anterior dorsal margin, and intersecting the posterior margin ab- ruptly at an angle of about 120°. Posterior dorsal margin sloping steeply, and meeting the posterior margin in a curve. Surface of shell beneath periostracum lusterless white, and smooth except for very fine incremental growth lines; an obtuse, rounded ridge running from the umbo to the posterior ventral angle marks the intersection of the posterior slope with the surface of the disk: this ridge is better defined in the left valve, where the posterior slope is occupied by a broad, very shallow sulcus. Hinge plate very narrow, bearing in the left valve a bifid ante- rior cardinal tooth and a lamellar posterior cardinal tooth; right valve with a bifid anterior cardinal tooth and a smaller, grooved posterior cardinal tooth. Ligament area shallow; posterior area not sharply defined. Pallial sinus
mildly discrepant between the valves: in the left valve, obliquely rising from the posterior adductor muscle scar, sinuous above, narrowing and extending forward about = of the distance between the adductor muscle scars, bluntly rounded anteriorly, about half confluent with the pallial line below; in the right valve obliquely rising from the posterior adductor muscle scar, smoothly rounded above, sloping in a straight line anteriorly, somewhat less bluntly rounded anteriorly, extending forward about # of the distance between the adductor muscle scars, about half confluent with the pallial line below. There is a slight posterior gape (about 1.5 mm in the holotype), and the posterior end is angled to the right almost imperceptibly. The anterior dorsal margin of the right valve overlaps the left valve slightly; in front of the umbo of the left valve there is a small incised area for the partial recep- tion of the overlapping portion of the right valve.
Measurements (in millimeters)
Length Height Diameter Holotype 42.0 Done 12.4 1* Paratype 40.8 opacd) 12.0 2¢ Paratype 44.5 23.8 13.9 3™ Paratype _ 28.6 15.1 8.3 4" Paratype 55.3 29.8 16.7
Type Locality: The holotype was collected live offshore from Plaquemines Parish, Louisiana, 28°59’ N Latitude, 89°30’ W Longitude, 18 m water depth, in silt substrate, salinity (interpolated from adjacent stations) 15%, at surface, 31%, at bottom, 9 June 1965.
Known Range and Habitat: Macoma pulley: was collec- ted west of the Mississippi Delta, offshore from Terre- bonne, Lafourche, Jefferson, and Plaquemines parishes, Louisiana, in mud substrate, in water depths of from
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Page 41
13 to 45 m, in bottom water having nearly normal salin- ity (30 to 33%). The unusually large 4" paratype was dredged dead in 19m water depth farther west, from a patch of sandy mud substrate 52 km south of the mouth of the Mermentau River, Cameron Parish, Louisiana.
Parker illustrates this species (PARKER, 1956; plt. 1, figs. 8A, 8B; the same pictures appear in Parxer, 1960, pit. 4, figs. 14A, 14B) as Macoma tageliformis. He lists several localities (PARKER, 1956, p. 315, table II) for M. tageliformis which probably refer to M. pulleyi. These localities are east of the Mississippi Delta: live specimens were common at the delta front, and dead valves were found in the shallow shelf area.
United States National Museum no. 189186, collected from Louisiana by L. R. Cary, is this species.
Disposition of Specimens: Holotype deposited in the Mu
seum of Comparative Zoology at Harvard University, no. 271577; 1* paratype (Figure 1) in the author’s collection; 2™ paratype in the U. S. National Museum; 3°: paratype
Figure 1 Macoma pulley Boyer, spec. nov.
First Paratype A. Interior, right valve C. Exterior, right valve
— matching valves B. Interior, left valve D. Exterior, left valve
in the Academy of Natural Sciences of Philadelphia; 4" paratype in the Bureau of Economic Geology, The University of Texas, Austin.
Remarks: Macoma (Psammacoma) pulleyi has been con- fused with the sympatric M. (P) tageliformis Dat, 1900. Macoma tageliformis was originally described from Cor- pus Christi Bay, Texas, but was not figured (Dau, 1900a, pp. 300, 315). Another description, also without figures, appeared about a month later (Dat, 1900b, p. 1055). Subsequently, illustrations were published of a specimen
from Puerto Rico (Dati « Simpson, 1901, plt. 55, figs. 10, 11, 15) which was identified as M. tageliformis. Dati « Smmpson’s figured specimen (U.S. National Museum no. 160497) is relatively much shorter than the holotype of M. tageliformis (U.S. National Museum no. 6086) ; the illustrated specimen also differs from the holotype in having a steeper posterior dorsal margin, which makes it look superficially like M. pulley:. Thus Datw’s choice of specimen to illustrate as Macoma tageliformis may have caused some of the confusion surrounding that species.
Collections of Macoma tageliformis from Louisiana agree perfectly with Datt’s holotype. Figure 2 is a speci- men of M. tageliformis from sandy silt substrate, 19 m water depth, 39km south of Rollover Bayou, offshore from Vermilion Parish, Louisiana.
Macoma tageliformis and M. pulleyi may easily be distinguished by the following differences:
a) Macoma tageliformis is more noticeably inequivalve, its left valve being more convex than its right.
b) In Macoma tageliform: ‘he ligament area is depressed, so that the surface of .he posterior area on either side is almost vertical and is set off from the rest of the shell by a rather sharp ridge; the posterior area is not so defined in Macoma pulleyi.
M oma pulley: has a rather abrupt posterior ventral an ,ie; also
Macoma pulley: bears a ridge delineating the poste- rior slope from the surface of the disk. These last two features are lacking in M. tageliformis.
Figure 2
Macoma tageliformis Dat, 1900
Matching valves. Offshore from Vermilion Parish, Louisiana A. Interior, right valve B. Interior, left valve C. Exterior, right valve D. Exterior, left valve
Page 42
e) The pallial sinus of Macoma pulleyi extends farther forward than that of MM. tageliformis.
The closest relative of Mfacoma pulleyi would seem to be the Miocene species M. holmesii Dati, 1900, from Duplin County, North Carolina.
Macoma pulleyi is dedicated to my friend Dr. T. E. Pulley, of the Houston Museum of Natural Science. Dr. Pulley is an authority on the mollusks of the Gulf Coast.
ACKNOWLEDGMENTS
The author wishes to acknowledge the support of a National Aeronautics and Space Administration fellow- ship and of National Science Foundation Grant GP-3600, and the use of the facilities of the Geology Department of Rice University. Dr. Robert R. Lankford supervised the project of which this study is a part; he also critically read the manuscript and contributed many helpful sug- gestions.
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LITERATURE CITED
Dati, WiLL1iAM HEALEY
1900a. Synopsis of the family Tellinidae and of the North American species. Proc. U.S. Nat. Mus. 23 (1210) : 285 to 326; plts. 2-4 (14 November 1900)
1900b. Contributions to the Tertiary fauna of Florida, with especial reference to the silex-beds of Tampa and the Pliocene beds of the Caloosahatchie River, including in many cases a complete revision of the generic groups treated of and their American species. Part V. Teleodesmacea: Solen to Diplodon- ta. Trans. Wagner Free Inst. Sci. Philadelphia 3 (5) : 949 to 1218; plts. 36 - 47 (December 1900)
Dai, WiLtiaM HEALEY & CHARLES TorrEY SIMPSON
1901. The Mollusca of Porto Rico. U.S. Fish Comm.
Bull. 20 (1): 351-524; plts. 53 - 58 (November 1901) Parker, Rospert H. ;
1956. Macro-invertebrate assemblages as indicators of sedi- mentary environments in east Mississippi Delta region.
Bull. Amer. Assoc. Petrol. Geol. 40 (2): 295-376; 32 figs.; 8 plts.
1960. Ecology and distributional patterns of marine macro- invertebrates, northern Gulf of Mexico. In: Recent sediments, northwestern Gulf of Mexico, ed. F R. SHeparp, EB. PHLEGER « T.H. Van ANDEL, pp. 302 - 337; 6 plts.; 17 text figs.
Amer. Assoc. Petrol. Geol., Tulsa, Oklahoma
Vol. 12; No. 1
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On Pseudopythina rugifera (CARPENTER, 1864) (Bivalvia)
WALTER NARCHI
Faculdade de Filosofia, Ciéncias e Letras da Universidade de Sao Paulo, Sao Paulo, Brasil
(9 Text figures)
INTRODUCTION
LitTLE Is KNOWN of the structure, functions of the organs in the mantle cavity, and the adaptations found in the Leptonacea, composed largely of commensal species, in correlation with their specialized mode of life.
PopHaM (1940, p. 549) refers to the biology of some species belonging to the genera Kellia, Lasaea, Montacuta, Mysella, Devonia and Galeomma. Ceratobornia cema (= Lepton cema Narcut, 1966) was intensively studied. Other genera were studied but no references were found for Pseudopythina.
Pseudopythina rugifera (CARPENTER, 1864) occurs on the Pacific Coast of North America from Alaska to Lower California (ApBoTT, 1954, p. 395; PALMER, 1958, p. 90). According to Kren (1937, p. 25) it ranges from 37° to 48° North Latitude. The species is well known in the eastern Pacific as an “ectoparasite” of the crustacean Upogebia pugettensis (Dana, 1852) and could be found attached by its byssus to the ventral surface of the poly- chaete worm, Aphrodita (OLpRoyp, 1924, p. 136; Mac- Ginitre & MacGrinrrig, 1949, p. 348; Parmer, loc. cit.; Boss, 1965, p. 186). Otproyp (Joc. cit.) states that all species of the genus Pseudopythina FiscHER, 1884, are commensals. In this paper observations on the structure, ciliary currents of feeding and digestion, and some other functional adaptations of P rugifera are studied.
The animals were found attached to the broad annu- lated foot of Aphrodita refulgida Moore, collected at Tomales and at Bodega Bay, Marin County, California (Figure 1). Several specimens were examined alive and the ciliary currents in the mantle cavity were observed with use of carmine, aquadag, and powdered carborun- dum. Others were fixed in Bouin’s fluid. Serial sections of 6m were made and the sections stained in Delafield’s hematoxylin, eosin and Alcian blue, to examine the gen- eral anatomy. The observations on living specimens were made at the Pacific Marine Station, Dillon Beach, Cali- fornia.
Figure 1
General view of several specimens of Pseudopythina rugifera attached to Aphrodita
SHELL anp MANTLE
The shell is small, oval-oblong, moderately obese and frag- ile, reflecting the protected habitat of this species. The umbones are close together, and located near the middle line of the shell. Lateral teeth are absent and one large central tooth (Figure 2) exists on each valve (CarPEN-
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Page4$ 0 Oe
Figure 2
View of the hinge of Pseudopythina rugifera (X 40)
TER, cited by PaLmeEr, 1958, p. 90). The shell is covered with a thin, light brown periostracum which is concent- rically wrinkled. The embryonic shell is still visible in the adult near the umbo. Foraminifera were found frequent- ly attached to the shell. The shell of the largest animal encountered in this study measured 6mm in length, 2.5 mm in height, and 1.5mm in width.
The species possesses both an external and an internal ligament, the latter being much more developed. As in Kellia suborbicularis (Montacu, 1803), the shell and the fleshy parts of Pseudopythina rugifera are white in color (OtprreLp, 1961, p. 257). In living animals the foot protrudes from the shell to a distance equal to half the length of the shell. The mantle edges, the inhalant and exhalant siphons do not extend beyond the shell valves as in Montacuta substriata (PopHam, 1964, p. 564).
As in Montacuta ferruginosa and M. substriata (OLp- FIELD, 1961, p. 260), there are only two pallial openings: a large, inhalant and pedal aperture in the anterior and ventral part of the body, and a small exhalant aperture posteriorly located. The inner mantle folds are fused be- tween these two apertures in a very short extension.
The exhalant siphon is shorter and formed by the inner mantle folds. The edges of this siphon bear small papillae of which one dorsal and one ventral papilla are slightly larger and can be seen protruding out of the shell.
The mantle edge has three folds. The outer fold is enclosed by the periostracum and has a flattened epi- thelium. The middle fold bears few papillae and secretes the periostracum. The inner fold contains the circumpal- lial nerve. The folds are very similar to those of Kellia suborbicularis (OLDFIELD, 1961, p. 260). In the dorsal part of the inner mantle fold, from the region of the stomach up to the pallial fusion, a tract of strongly cili- ated cells occurs. This tract is concerned with the rejection of particles from the mantle. The free edge of the mantle surrounding the inhalant siphon and pedal opening is also ciliated. Particles falling on this edge are passed into the mantle cavity. ,
Tue CTENIDIA
Both demibranchs are present in Pseudopythina rugifera (Figure 3), but the outer demibranch (od) is less than half the depth of the inner (id). Only the inner demi- branch has a food groove along its ventral edge. Lam- mellae are flat and homorhabdic, as found in the Leptoni- dae (Atkrns, 1937, p. 391). Behind the foot (f), the left and right inner demibranchs are joined together in the median plane. As in Kellia suborbicularis (OLDFIELD, 1961, p. 263), both outer and inner demibranchs on each side are fused ventrally to the mantle, in the region where the fused inner folds of the mantle separate the common inhalant and pedal aperture from the exhalant aperture.
Hin
Figure 3 Pseudopythina rugifera (CARPENTER, 1864) Mantle cavity viewed from the left side after removal of the left shell valve and mantle lobe, showing ciliary currents.
a-— anus am — anterior adductor muscle _ b — byssus arp — anterior retractor pedis muscle dd — digestive diverticula exs — exhalant siphon f — foot g — foot groove id — descending lamella of inner demibranch __ li—inner labial palp lo—outer labial palp | oa—ascending lamella of outer demibranch prp — posterior retractor pedis muscle | w — waste material pm — posterior adductor muscle te — tentacle
The gill filaments are numerous. Slender interfilamentar junctions are numerous but interlamellar junctions are few. This condition is found in other species where the incubatory habit occurs (OLDFIELD, 1961, p. 263).
The ciliary mechanism in the ctenidia of Pseudopythina rugifera is similar to that of Kellia suborbicularis (At-
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KINS, 1937, p. 389). The ctenidia and their ciliation are as in Type C(1) of Atkins (loc. cit.).
There is no interruption of the latero-frontal cilia at the ventral tip of the filaments of the ctenidia, but rather a bending of the filaments. The frontal currents on the outer demibranch are directed ventrally on the ascending lamella, bend at the free edge and flow dorsally on the descending lamella. The frontal cilia are not modified. In the free edge of the outer demibranch no longitudinal currents occur.
The frontal currents on the inner demibranch are direc- ted ventrally on the ascending and descending lamellae. In the free edge of the inner demibranch an oral longi- tudinal current occurs. Other oral currents occur between the bases of the two demibranchs of each side of the body.
Along the marginal grooves of the inner demibranch shorter guarding cilia exist. On each ventral tip of the filaments these cilia beat as a group, moving particles to the anterior part of the body.
The fine frontal cilia are continued on each side and beat directly to the ventral part.
eT EAI WEN oie tide
OH % a BN
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The long lateral cilia form an inhalant current and the frontal cilia convey food particles along the filament to the food groove.
There is one type of latero-frontal cilia: the eu-latero- frontal cilia which are fused, large, and prevent the loss of food particles into the supra branchial chamber.
As in Kellia suborbicularis (OLDFIELD, 1961, p. 264), guarding cilia exist on both sides of the food groove and these cilia prevent the entrance of coarse particles into the groove. ATKINS (1937, p. 360) suggests that guarding cilia occur when the animals live in a silt or muddy sub- strate.
MUSCULATURE
The anterior adductor muscle (Figure 4, am) is slightly larger than the posterior adductor muscle (pm). The re- jected material is violently shot out of the pallial cavity by a sudden contraction of the adductors.
PopHam (1940, p. 564) describes the same phenomenon for Kellia suborbicularis. OLDFIELD (1961, p. 264) believes
Figure 4
Pseudopythina rugifera (CARPENTER, 1864) Diagrammatic representation of the organs in the mantle cavity
am — anterior adductor muscle
arp — anterior retractor pedis muscle bl — byssogenous lamella
dd — digestive diverticula i — intestine
au — auricle bgi- main byssus gland cg — cerebral ganglion f — foot g — foot groove ia — ascending lamella of inner demibranch ss — style sac
oa — ascending lamella of outer demibranch
prp — posterior retractor pedis muscle ve — ventricle
id — descending lamella of inner demibranch li — inner labial palp _lo — outer labial palp
k — kidney bv — ovary oe — oesophagus
pm — posterior adductor muscle r—rectum s—stomach
pg — pedal ganglion
vg — ventral ganglion
Page 46
that this is probably essential in species which live in a sandy or muddy habitat and prevents the danger of their silting up. Each adductor muscle is subdivided equal- ly into two parts, as in Kellia and Montacuta.
There are two pairs of muscles of the foot: a pair of anterior retractor pedis muscles (arp) and a pair of pos- terior retractor pedis muscles (prp).
As in Kellia and Montacuta, there is no elevator pedis muscle. The anterior retractor pedis muscle is completely subdivided into a smaller retractor pedis muscle and a larger byssus retractor muscle. As in Montacuta substriata (OLDFIELD, 1961, p. 267) the well developed byssus mus- culature is related to the high development of the byssus apparatus in this species. In Pseudopythina rugifera the protractor pedis muscle runs through the lower part of the anterior retractor pedis muscle, but is inserted to- gether with the byssus retractor muscle (br), while in M. substriata they have a separate origin from the shell (OLpFIELD, 1961, p. 267).
THe FOOT
The foot is large and though laterally compressed, has a flat creeping sole by means of which it is capable of active locomotion. It is slender and, when fully distended, is half the length of the shell, but it can be completely withdrawn when the shell valves are closed. The large pedal aperture combined with the inhalant aperture per- mits the foot to move in a wide angle. As in Montacuta substriata (PopHam, 1940, p. 565), rocking movements are possible because of the gape and the large size of the pedal opening. The byssus cavity (bg) lies posteriorly in the foot and opens by way of a byssus canal into a groove (g) which extends on the ventral side almost to the tip of the foot. In M. substriata (PopHaM, loc. cit.) two or three threads are produced but in Pythina rugifera the number is greater.
The ventral and ventro-lateral surfaces of the foot are covered by a ciliated columnar epithelium, as are the surface of the byssogenous lamellae (bl), the byssus canal and groove.
The viscera do not extend into the foot. In the foot there are many muscle fibers and connective tissue with large blood spaces.
Pseudopythina rugifera lives attached to the foot of the sea mouse by a large byssus (b) composed of a large number of threads. The byssus cavity is embedded in the main byssus gland and is divided by a fold into two large longitudinal parts (Figure 5). Each part is divided into 10 to 12 slit-like compartments by the byssogenous lamel- lae. Each lamella is composed of connective tissue and
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Figure 5
Pseudopythina rugifera (CARPENTER, 1864) Byssus gland and byssus thread
fine muscle fibers from the byssus retractor muscle. A ciliated columnar epithelium covers the lamellae and is composed of low columnar cells. The byssus apparatus of P. rugifera is very similar to that found in Potidoma sub- trigonum (Derrovux, 1961, p. 119).
The glandular cells of the main byssus gland (bgi) surround the byssus cavity. From these cells, in which the cytoplasm laden with fine granules, stains in aniline blue, long slender ducts lead to openings between the ciliated epithelial cells covering the surfaces of the byssogenous lamellae, in the byssus cavity. Thus the secretion of the main byssus gland forms a coating to the lamellae, and these sheets of secretion coalesce to form the stalk of the byssus.
The byssus canal is ciliated on its anterior and lateral walls and the byssus groove is ciliated throughout its entire length.
Vol. 12; No. 1
THE VELIGER
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The main mucus gland occupies the anterior part of the foot and extends along both sides to the posterior end of the foot. From these mucus cells slender ducts open on the byssus groove on the ventral and ventro-lateral surfaces of the foot.
The construction of the byssus threads by adult animals was observed in the laboratory. A new byssus thread is constructed in 30 seconds and this velocity is probably due to the habits of the animal. To build a new byssus thread the foot is placed on the sole of the sea mouse. It becomes temporarily attached, apparently by a sucker- like action, and does not move. Only the tip of the foot moves laterally back and forth, until the byssus thread is completed.
Pseudopythina rugifera, detached from the sole of Aph- rodita, with very active locomotion attached itself to the ventral part of the animal in a few seconds. As in Mont- acuta substriata (PopHaM, 1940, p. 566), the surface of the foot is strongly ciliated. Particles move rapidly across the sides of the foot from the tip to the heel and are passed off into the main rejection current concerned with the rejection of waste material, which passes out between the shell valves in a posterior and ventral direction im- mediately behind the foot.
LABIAL PALPS
The labial! palps are relatively small; their opposed sur- faces are covered by cilia and they have 9 transverse ridges. The ridged and grooved surfaces function as a sorting region. Particles of food and other material are swept onto the palps from the food groove of the inner demibranch. On the crests ot the folds, particles are carried forward from fold to fold towards the mouth. On the floor of the grooves, between adjacent folds, particles are driven to the ventral border of the palp and from there moved to the tip of the palp where they are rejected.
The ventral tips of the anterior filaments of the inner demibranch are not inserted into a distal oral groove, although the antero-ventral margin of the inner margin of the inner demibranch is fused to the inner palp lamella and belong to the Category III of the association of ctenidia and labial palps (Stasex, 1963, p. 91).
THe ALIMENTARY CANAL GENERAL STRUCTURE
The small size of the specimens made it difficult to study and observe the internal structure of the stomach in great detail. The alimentary canal was dissected in
specimens that had been preserved in alcohol. The in- ternal structure of the stomach was studied in living specimens. The stomach was opened from the surface by a mid-dorsal incision through the roof, and the right side of the stomach was drawn downwards. The ciliary cur- rents were determined with the aid of carmine, aquadag and fine carborundum particles. The nomenclature used by GraHam (1949), Owen (1953), PurcHoN (1955), and Rem (1965) has been followed.
The mouth opens into the oesophagus ( oe) which joins the stomach (s) at the anterior and ventral part, which is thin-walled and globular. The stomach is approximately cylindrical in shape and is