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Bijdragentot de Dierkunde, 62(2) 117-120(1992) SPBAcademie Publishingbv, The Hague Peraclis valdiviae from the Banda Sea (Mollusca, Pteropoda) S. van der Spoel Instituteof TaxonomieZoology, University ofAmsterdam, The Netherlands Keywords: Pteropoda, Peraclis valdiviae, vertical distribution, BandaSea Abstract intact as reconstructed inFig. 3 its height may be6 mm. The other three specimens are only slightly TheshellofPeraclisvaldiviae (Meisenheimer,1905)from Banda smaller.Thecalcareous shellsareopaquewhitebut Sea specimensproved tobeofaslenderPeraclis bispinosa-like thisis the effect ofthepreservation thatdid disap- type. Thespecimens showed avery shallow distribution in the pear colourand transparency. Banda Sea due torelatively high deep-watertemperatures and vertical mixing. Theshell has 3.75 whorls; thebody whorl is very large. The spira is rather high, pointing above the body whorl. Thecalcareous, sinistral shell is cov- Introduction.- The deep-sea species Peraclis val- eredwith a hexagonal calcareous reticulumexcept for theembryonic, first, whorl and the last halfof diviae(Meisenheimer, 1905) israrely collectedand intact specimens with shells are only reported by the body whorl. On the last whorl a thickenedrib Tesch(1948). Hewas the first to describetheshell, runs parallel to thesuture; inbetweenthisthick rib but this description could not be completely ac- and the suture, transversal rims are found and curate as the specimens were rather damaged. growth lines are visible. MaterialfromtheSnelliusIIExpedition* collect- Growthlinesare distinctover thewholeshellbut edintheBandaSeaintheperiod July 1984-March mostprominent on thebody whorl. As can be con- 1985(Schalk, 1990) provided fourspecimens with cluded from the growth lines nearthe aperture of shells. Thesample is preserved in alcohol 70%. In theshell, asmallanteriorspine had beenpresent on this paperthe shell is more fully described. As this theaperture, probably supported by thethickened bathypelagic snail occurs in a sample of less than rib. The wavy, spiral ribs around the body whorl, 500m depth, a typical verticaldistributionpattern 9 or 10 in number, becomestrongernearthe aper- in the Banda Sea is considered. ture; thefourcentralonesoftheseare morepromi- nentthanthe outerones. Theapertureborderisdis- Description oftheshell.— Themeasurementsofthe continuous, spindle-shaped; a verybroad columel- largest ofthefourspecimens (Figs. 1 & 2) are: shell lar membrane is present forming a spoon-like height 5 mm, maximumwidth4.4 mm,aperture4.8 protrusionat theundersideoftheaperturesupport- ed by the columella. mm in height and 3.6 mm in width, greatest di- ameter oftheoperculum 5.4 mm. Whenthe shellis In an intact specimen a pointed rostrum is sup- * Research has been carried outasapart ofthe Snellius IIExpeditionorganizedby the Netherlands Council ofSea Research (NRZ) and the Indonesian Institute ofScience (LIPI). 118 S. van der Spoel - Peraclis valdiviaefrom the BandaSea Figs. 1-3.Peraclisvaldiviae: 1,shell in aperturalviewwith the softparts and operculumvisible;2,shell from dorsal inslightlyoblique position, the parts broken offaredotted;3, reconstruction ofcompleteshell in aperturalview. posed to be present as illustrated in Fig. 3. The operculum (Fig. 4)with4.5 whorlsis nearly round, very thinand flexible.Thefirst whorls andthe last oneare coiledina higher level thanthelastbutone. Thetypical striationofthe operculum, describedby Tesch (1948), could not be found in the present specimens; only an irregular reticulatedpattern is foundin the centre of the whorls. Discussion. - Theillustrations oftheshell given by Tesch (1948) gavethe impression as ifthe shell is rather depressed though thespireis high. Ascan be Figs. 4. Peraclis valdiviae: the extremelythin operculum from seen from theillustrationspresented herethe shell the outsideand in cross-section. is slender and resembles more that of Peraclis bispinosa Pelseneer, 1888andthat ofProcymbulia the shell characters that Gilmer (1990) considered philiporum Gilmer, 1990. The statement of Tesch to separate Procymbulia from Peraclis can, thattheshellismuchmore depressed thaninforex- however, be foundalso invariousPeraclisspecies. ample P. bispinosa seems incorrect as the shell is Gilmer (1990) stated "The thin shell could not be elongate. The shells of both Procymbulia philipo- removed from the animal consequently it dis- ... rum and Peraclis valdiviaeare slender. The spiral solved after several weeks inthepreservative", so ribs on the body whorl characterize P. valdiviae that one can concludethat theshell is described as from the other species inthe genusindeed. seen in the tissues and "pseudoconcha" in an ag- Gilmer (1990) described Procymbulia philipo- gressive preservative. Thereforethe description of rumas a closerelativeofPeraclisvaldiviaeandstat- shell structureandsculpture are doubtfulandseem edthatthegeneraPeraclisandProcymbulia should not sufficient to supportthe separatestatusofthe be kept separate as the latter is intermediatebe- genusProcymbulia. As a consequenceIproposeto tween thePeraclididae and the Cymbuliidae. All retainthegeneric name Peraclisalso forthespecies Bijdragen tot deDierkunde, 62 (2) - 1992 119 Fig.5.DistributionofPeraclisvaldiviae and related forms:circles = samplesfrom depthbelow 500m;triangles =samplesfrom depth shallower than 500 m,largetrianglethe presentmaterial; 1 = supposedborder ofdeepoccurrence; 2 = polarmostborder forshallow occurrence. valdiviae,philiporum, andmichaelsarsi(Bonnevie, The Discovery Expedition specimens identified 1913). by Massy (1932)are allfromSubantarcticandAnt- arctic waters collectedbetween0 and 200m depth. Tesch (1946, 1948) described Peraclis valdiviae P. valdiviaethusshowsa very pronounced subtrop- collected by the Dana Expeditions. In the list of ical submergence at 40-45°Nand 40-45°S. Indo-Pacificspecimens published byTesch(1948)a The Snellius II specimens are collected at recordof0-200m depth isgiven butthisis aprint- 395-500m depth in the Banda Sea between 12.18 ing error for asample with 2000 m wire out. The and 12.58hat a water temperatureof9.5-7.9°C. specimens from the Atlantic described by Tesch Thisis a very shallowsampling depth for thisspe- (1946) are identified as Procymbulia ( = Peraclis) cies. In theBandaSea shallowoccurrence of deep- sp. as they could not all be assigned to a species. seaanimals has been reported already by Van der Thespecimens were alsorather small. Itis thus not Spoel & Schalk (1988); among thesewas the deep- certainthatthe specimens collectedinthetwo sam- sea thecosomatous pteropod Clio andreae Boas, ples with300and600m wireout belong to Peraclis 1886, reported from0-102 m depth. As an expla- valdiviae.Itmaybe concludedthat in theAtlantic, nation for this shallow occurrence the strong and Indian, andPacific Oceansbetween40°Nand40°S deepverticalmixingandthe deviating, higher, tem- P. valdiviaeoccurs below2000m; near40°Nand S peraturesat depthinthe BandaSeawere given (Van the depthofoccurrence decreasesto700or 1000m. derSpoel & Schalk, 1988). Itisremarkablethat all 120 S. van derSpoel - Peraclis valdiviaefrom theBanda Sea the deep-seaspecies reported fromrelatively shal- 1-69,pis. I-IX. low depths in the Banda Sea are species showing Gilmer,R.W., 1990.Procymbuliaphiliporumnewspecies, with subtropical submergence. P. valdiviae confirms a discussion of the genus ProcymbuliaMeisenheimer, 1905 (Gastropoda:Thecosomata).Nautilus, 104 (4): 11-119. this as it shows also strong subtropical sub- Massy, A.L., 1932. Mollusca: Gastropoda Thecosomata and mergence. Gymnosomata. Discovery Rep., 3:267-296,pl. XXXIX. There are two types of deep-sea species: those Meisenheimer,J., 1905.Pteropoda.Wiss.Ergebn. dt.Tiefsee- primarilyadapted to lowtemperatures atdepth(de- Exped. "Valdivia", 9: [i-iii], i-vi, 1-314, Atlas Pis. veloped recently afterthe Oligocene when cooling I-XXV1I, [1-56], maps 1-IX. Pelseneer, P., 1888. Report on the Pteropodacollected by of deep water started)and those adapted to depth H.M.S. Challenger, during the years 1873-1876, 2. The only (developed already afterthe Mid-Cretaceous Thecosomatareports onthe scientificresultsofthe voyageof directlyaftertheriftingofthedeep seainthenorth- H.M.S.Challenger,duringtheyears 1873-1876. Rep. scient. ern Atlantic) (cf. Van der Spoel et al., 1990). The Results Voy. Challenger,(Zool.)23(1): 1-132,pis. I—II. species withsubtropical submergence clearly follow Schalk,P.H., 1990.Spatialand seasonal variation inpteropods (Mollusca)ofIndo-Malayanwaters related towatermassdis- thelowtemperaturesfoundat depthandmorenear tribution. Mar. Biol., 105 (1): 59-71. the surface in polar areas. Probably only these Spoel, S. van der, A.C. Pierrot-Bults & P.H. Schalk, 1990. temperature-adapted, and phylogenetically youn- Probable Mesozoic vicariance in the biogeography of Eu- gerspecies come closerto the surface inthe Banda phausiacea. Bijdr. Dierk., 60 (3/4): 155-162. Sea and comparable oceanic areas. Spoel, S. van der & P.H. Schalk, 1988. Uniquedeviations in depthdistribution ofthe deep-seafauna. Deep-Sea Res., 35 (7A): 1185-1193. Tesch,J.J., 1946. The thecosomatouspteropods, 1.The Atlan- Literature tic. Dana Rep.,28: 1-82,pis. I—VIII. Tesch, J.J., 1948.The thecosomatous pteropods,2. The Indo- Pacific. Dana Rep., 30: 1-45,pis. I—III. Bonnevie, K., 1913 (reprinted 1933). Pteropoda from the "Michael Sars" North Atlantic deep-seaExpedition. Rep. scient. Results Michael SarsN.Atlant.deepSeaExped.,3(1): Received: 10March 1992