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IntroductionFor animals living on the seafloor, a planktonic larvalstage is a critical phase of the life cycle. Larval dispersalprovides ecological and genetic connections amongcommunities in patchy habitats such as hydrothermalvents. Temporal variation in larval supply to benthiccommunities can lead to fluctuations in the size andgenetic composition of adult populations. On longtime scales, barriers to dispersal can lead to speciationand are thought to be fundamental factors in generatingbiogeographic patterns and regional biodiversity.Despite the importance of the larval phase, very littleis known about larval dispersal in the deep sea, evenat hydrothermal vents where the habitat is patchy andtransient, and larval exchange critical to the survival ofendemic species.General difficulties of larval identification for deepseastudies include the scarcity of larvae in planktonsamples, the fact that the adults may be unknown, andthe difficulty of matching larval morphotypes to adultforms. However, some hydrothermal vent habitats havewell-characterized benthic communities with relativelylow species diversity and relatively high biomass andfecundity, resulting in large numbers of larvae in theplankton compared to typical deep-sea habitats. In addition,a large portion of hydrothermal vent communitiescan be comprised of gastropods, which can, inmany cases, be identified by protoconch morphology.For example, gastropod larvae collected near hydrothermalvents in the eastern Pacific have been identifiedmorphologically under light and electron microscopy(Mullineaux et al., 1996).Since the discovery of hydrothermal vents thirty yearsago, researchers have been collecting larvae in studiesto explain the colonization of these oases in the deep(e.g. Lutz et al. 1984, Turner et al. 1985, Kim and Mullineaux1998). Recent emphasis has been placed ontime-series collections of larvae in multi-disciplinarystudies of larval dispersal and supply to vent communities,such as the LADDER project at the East PacificRise (http://www.whoi.edu/projects/LADDER/). Thepurpose of this photographic identification guide isto serve researchers studying hydrothermal vent larvaein previously collected and future samples. The photographsmay also be useful to those studying newlysettled colonists.Collection and preservation of larvaeFor this first edition of the identification guide, larvaewere collected near hydrothermal vents at the EastPacific Rise (EPR) 9°N site. Specimens were obtainedover a 15-yr period, beginning with collection by netsand pumps with small-volume samples from 1991 -1995 (Kim and Mullineaux, 1998), pumps with largevolumesamples from 1998 - 2007 (Mullineaux et al.,2005; Beaulieu et al., 2009), and time-series sedimenttraps from 2004 - 2007 (Adams, 2007; Adams andMullineaux, 2008). Net tows, plankton pumps, andsediment traps do not sample larvae in equal proportions– some are better collected by one method or anotherand a combination of methods is likely to give amore complete description of the larval species compositionof a particular site (Beaulieu et al., 2009).For our recent studies at the EPR, large-volume pumpswere used to collect discrete plankton samples overMethods1-day periods (McLane Large Volume Water TransferSystem WTS-LV50; McLane Research Laboratories,Inc., Falmouth, MA, USA). We pumped 30 L min -1(500 cm 3 s -1 ) over a filter comprised of 63µm Nitexmesh, yielding ~40 m 3 pumped per day. For time-seriessampling we used a conical, time-series sediment trapwith sampling aperture 0.5 m 2 and 21 cups (McLanePARFLUX Mark 78H-21 Sediment Trap; McLane ResearchLaboratories, Inc., Falmouth, MA, USA). Priorto deployment, we filled the cups with a solution of20% dimethylsulfoxide (DMSO) in ultrapure watersaturated with NaCl. We chose this preservative to allowfor molecular genetic analyses of the collected specimens(e.g. Comtet et al., 2000). The pumps and sedimenttraps were deployed on autonomous subsurfacemoorings, with the samples collected between 2 and175 m above bottom (mab) depending on each mooringconfiguration. Moorings were positioned within ornear (< 2 km off-axis) the axial summit trough.3


MethodsFor the large-volume pump samples, after recovery ondeck the filter holder was removed into a 20-L bucketwith chilled, filtered seawater. All subsequent handlingof the sample occurred in a cold room (4º C).Samples were carefully rinsed from the filter using asquirt bottle with chilled, filtered seawater. Many ofthe collected specimens were alive upon retrieval of thepump. We briefly examined the samples live under adissecting microscope prior to collecting onto a 63µmsieve, rinsing with fresh water, then preserving in 95%ethanol for examination at our laboratory. For the sedimenttrap samples, after recovery of the mooring wephotographed the cups and stored them at 4º C priorto shipment to our laboratory for examination.A.B.A. McLane Large Volume Water Transfer SystemWTS-LV50 Plankton Pump.Photo by Carly Strasser, WHOI.B. McLane PARFLUX Mark 78H-21 Sediment Trap.Photo by Skylar Bayer, WHOI.Sorting and photographing larvaeFor sorting at our laboratory within a few months aftereach cruise, samples were poured over nested 300µmand 63µm sieves, and each fraction was rinsed withfresh water into a petri dish. We sorted larvae undera dissecting microscope at 25X, with identificationgenerally at 50X; some specimens required examinationunder a compound microscope at 100X. Individuallarvae were manipulated with a fine paintbrush orshort length (~5 mm) of human hair glued to the endof a wooden stick. Individuals were transferred with apipette set to ~10µL. For examining under the compoundmicroscope, individuals were transferred to awelled slide filled with fresh water. We moved the coverslip gently side-to-side to roll the larva into an appropriateposition for measuring and photographing. Larvaesorted from both sediment trap and pump sampleswere saved in 95% ethanol and stored in Lauren Mullineaux’slaboratory at Woods Hole Oceanographic Institution.We do not recommend transfer from DMSOsolution to ethanol for future studies because it apparentlycaused tissue degradation for polychaete larvae.Some gastropod larvae were dried and imaged usingscanning electron microscopy (SEM). These specimenswere placed on 1.25cm diameter circular cover slipswhich had been previously coated with a thin layer ofwhite Elmer’s glue, which was allowed to dry. The smallamount of ethanol clinging to specimens dissolved theglue enough to stick them in place. The cover slip withthe specimen was then attached to a SEM stub andsputter-coated for 1 min using Samsputter. These wereexamined using the JEOL 840 scanning electron microscopeat the Marine Biological Laboratory (MBL).Species identifications were made using a variety ofsources. For gastropod protoconchs we relied heavilyon the literature, which contains detailed SEM photographsof protoconchs for many species from theEPR 9°N site. For species for which the protoconchis unknown, we occasionally would image the protoconchof an identified juvenile for comparison (e.g.,Gorgoleptis spiralis). For the identification of Bythograeasp. zoea, we are indebted to Ana Dittel (University of4


TerminologyGastropod terminologyWith a few exceptions, we photographed the protoconchsin the apical view, with the aperture on thebottom right-hand side of the picture, as illustrated inthe diagram below. This is the side that remains visibleafter the larva settles and begins post-larval growth, sothe photos can be directly compared to juveniles andadults that have retained their protoconchs. The moreproximal (“posterior”) portions are to the left in thediagram, the more distal (“anterior”) to the right. Theaxis of coiling is the point around which the coil ofthe shell rotates. Most of these larvae are planispiral,or nearly so, meaning that their coiling is more or lessin one plane. This gives them a sort of pseudo-bilateralsymmetry and we will sometimes refer loosely to the“base” (at the bottom left-hand side of the diagram)and the “height” of the shell, as well as to the “right”side (facing out of the page in the diagram), the “left”side (facing into the page in the diagram), the “bottom”(the view with the aperture facing out of thepage) and the “top” (the view with the aperture facinginto the page). Many of these protoconchs have anaperture rim; usually this is visible only with the lightmicroscope.Most of these larvae have some form of sculpture ontheir shells. In the planispiral species, there are threetypes, with some degree of overlap:Pitted sculpture, which is typical of the Family Lepetodrilidae,consists of depressions in the surface of theshell. These may be small or large, shallow or deep andmay be widely scattered or so close together that theentire surface of the shell is pitted. Sometimes the pitsmay follow the curve of the shell, so that the sculptureappears to form lines. Pitted sculpture often appearsgrainy under the light microscope.Lineate sculpture, found in the Family Peltospiridae,is a series of regularly-spaced ridges that follow the curvatureof the shell. The lines usually start at the axis ofcoiling, though there are exceptions, and extend mostof the way to the aperture. There may be other formsof sculpture present as well, such as tubercles - raisedbumps - as found in Lirapex granularis.Reticulate sculpture is formed by raised ridges, butinstead of following the curvature of the shell, theyspread out to form a mesh. This network may be veryregular and interconnected or consist of relatively fewirregularly forking lines. Sometimes the mesh coversthe entire shell; more commonly it is limited to themore proximal portions of the shell. This kind of sculptureis found in the Neomphalidae.Terminology for planispiral forms, with protoconch I.Apical view.“Top”Pitted sculpture“Height”Proximal,PosteriorAxis of CoilingDistal,AnteriorLineate sculpture“Base”“Bottom”Aperture RimAperture WidthReticulate sculptureDiameter6


Terminologyerture opening facing out of the page, the aperture willbe to the right. Our photographs usually show boththe apical view, to illustrate PI, and the aperture view,which shows the larva as it is usually found in samples.In these species, we refer to sculpture that follows thecurvature of the shell as spiral and sculpture that radiatesout from the axis of coiling as axial.Axial SculptureTerminology for coiled forms,with both protoconchs I and II.Apical view.Protoconch IIProtoconch ISpiral SculpturePolychaete TerminologyWe are not qualified to give a detailed description oflarval polychaete terminology, but for those unfamiliarwith the group we have included definitions for a fewof the standard terms. The first segment of a polychaete(the “head”) is called the prostomium; the final segment(“tail”) is the pygidium. The head may includeappendages such as antennae (shown here) and palpsand also one or more pairs of tentacular cirri, whichare often on the second segment (the peristomium, notshown here). The pygidium may have anal cirri.The main body segments often have fleshy, paired“feet” (parapodia) protruding to the sides, which havebunches of bristles (chaetae) at the tips. A body segmentwith chaetae is referred to as a chaetiger. Chaetigersmay have cirri or branchiae (gills) as well (notshown in this diagram).chaetaeparapodiaFor coiled forms we use slightly different terminology.These shells generally show two different growth stages,often with different types of sculpture. The earliestshell, protoconch I (PI), usually is formed while thelarva is non-feeding, the second, protoconch II (PII) isformed after the larva begins feeding in the plankton.All of these shells are right-handed, meaning that whenthe shell is oriented with the apex at the top and the apanteriorantennaeposterioranal cirriTerminology for polychaetelarvae and juveniles.Dorsal view.prostomiumtentacular cirruspygidiumchaetigers7


GASTROPODACan be confused with:Gorgoleptis emarginatus strongly resembles G.spiralis in everything but size; G. spiralis isabout 30µm smaller.Gorgoleptis sp. 3. This presumed Gorgoleptisspecies is also about 30-35µm larger than G.spiralis. The point at the outer edge of theaperture is more pronounced in this group, itlacks the side points and is much less common.8


Gorgoleptis spiralis McLean, 1988. Family Lepetodrilidae.GASTROPODASize: 140-150µmMorphology:Gorgoleptis spiralis is one of three presumed Gorgoleptis morphswe find in plankton samples at EPR 9°N. It has coarse pittedsculpture in rows that follow the curve of the shell. The mostdistinctive feature of these protoconchs is the scalloped edgesof the aperture, with sharp points at the anterior edge and oneither side. There is a narrow aperture rim, tapering towardthe posterior edge. The protoconch matches that of Gorgoleptisspiralis in size and sculpture, but the scallops are not preservedin post-larval specimens, making the identification somewhattentative.Frequency:Pump EPR 1999-2000: FrequentPump EPR 2004: FrequentTrap EPR 2004-2005: FrequentClypeosectus delectus is about 25µm larger thanG. spiralis. The sculpture is also very similar,but the aperture is nearly straight, rather thanscalloped.Pointy apex is about 10µm larger than G.spiralis. The sculpture is also very similar, butthe aperture is nearly straight, rather thanscalloped.9


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“Pointy apex” (unknown slit limpet in Mullineaux et al., 2005).Family ?Lepetodrilidae.GASTROPODASize: 155-160µmMorphology:These are small protoconchs with dense, shallow pittedsculpture over the entire shell, forming lines on the outer distalface. The shell itself is rather angular in overall appearance,with portions of the outline appearing almost flat. The apertureis slightly sinuous, with a narrow rim visible under the lightmicroscope. The protoconch resembles Sutilizona theca, a slitlimpet described from EPR 13°N in McLean (1989; SEM Fig.4F).Frequency:Pump EPR 1999-2000: FrequentPump EPR 2004: FrequentTrap EPR 2004-2005: FrequentCan be confused with:Clypeosectus delectus isvery similar in size andappearance to pointyapex. It is possiblethat both protoconchsrepresent differentforms of the samespecies (or possiblytwo species in the same genus), but because ofconsistent differences in their morphology, wehave kept them separate for the present. Pointyapex can be distinguished by the more angularshape of this species, by its slightly smaller size(160μm vs. 175μm for Clypeosectus) and by itsnarrower aperture rim.Lepetodrilus spp.Lepetodrilus spp. havefiner pitted sculpturethat doesn’t usuallyshow lineation. Thebase of the shell linesup with the aperturein these protoconchs,whereas in pointy apex it protrudes below.Pointy apex is about 15-20µm smaller.Gorgoleptis spp.,especially G. spiralis,pictured at left. AllGorgoleptis specieshave a sharp point atthe outer edge of theaperture, and two havepoints at the sides aswell. Gorgoleptis spiralis is slightly smaller thanpointy apex; the other two Gorgoleptis speciesare about 20µm larger.11


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Unknown benthic sp. A Family ?Neomphalidae.GASTROPODASize: 160-170µmMorphology:This is a small distinctive protoconch. Nearly all the ventprotoconchs are planispiral, with a very slight right-handtwist. This one, however, has a distinct left-hand twist, so thatif you try to set it on its left side in our standard orientationfor photographing the protoconchs, it will roll to show theaperture, as in the SEM above. It has overall regular reticulatesculpture and may be a neomphalid.Frequency:Pump EPR 1999-2000: CommonPump EPR 2004: CommonTrap EPR 2004-2005: CommonCan be confused with:Unknown 5 looks very much like UnknownA, though it is about 10µm larger. It has adistinct flare to the aperture rim, which iswider than that of Unknown A. The easiestway to distinguish them quickly is to roll them;Unknown A will generally roll to expose theaperture, while Unknown 5 is stable on its side,as shown at left.Lepetodrilus spp. is about 10µm larger thanUnknown A. Lepetodrilus spp. has pittedsculpture rather than reticulate and is also stableon its side.13


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Unknown neomphalid 5 Family ?Neomphalidae.GASTROPODASize: 170-180µmMorphology:This is a small bulbous protoconch with overall fine reticulatesculpture. It has a straight aperture with a narrow rim whichflares out all around. Seen from the side, the aperture and thelowest part of the base line up. From this angle the aperturemeasures about 2/3 of the total diameter of the shell. Itresembles some of the Lacunoides protoconchs in the literature(especially L. vitreus from Juan de Fuca; Warén and Bouchet,2001, p.167, Figure 29e), but neither of the described specieshas been reported from EPR 9°N, to our knowledge. Becauseof the reticulate sculpture, we suspect that it is a neomphalid.See also Fig. 4A in Mullineaux et al. (1996)Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: CommonTrap EPR 2004-2005: CommonCan be confused with:Lepetodrilus spp. isthe most likely tobe confused withUnknown 5. They areof similar size, and inboth the apertures arestraight and line up withthe base of the shell. InUnknown 5, however, the aperture, when seenfrom the side, appears to take up about 2/3of the shell diameter, whereas in Lepetodrilusit is about half. Unknown 5’s aperture rim isnarrower and it flares out to the sides and at theouter edge. Lepetodrilus has pitted sculpturerather than reticulate, but this is not usuallyobvious under the light microscope.Unknown benthic sp. Ais about 10µm smallerthan Unknown 5, butis similar in appearanceand also has reticulatesculpture. It has a slightleft-hand twist, whichtends to make it roll toexpose the aperture. Unknown 5, however, isstable resting on its side.Clypeosectus delectusis similar in size toUnknown 5, but theaperture does not forma straight line with thebase, and it has coarsepitted sculpture, ratherthan reticulate.15


GASTROPODACan be confused with:Unknown 5.Lepetodrilus spp. hasa more streamlinedappearance, with theaperture length abouthalf the diameter of theprotoconch. Unknown5 is more rounded andthe aperture is closer to 2/3 the protoconchdiameter. The aperture rim is narrower inUnknown 5, and it flares out at the anterioredge and at the sides. Unknown 5 has reticulaterather than pitted sculpture, but this may not beapparent under the light microscope.Gorgoleptis emarginatusis approximately thesame size as Lepetodrilusspp. Its sculpture ismuch coarser, and ithas points at the outeredge and both sides ofthe aperture, giving ita scalloped appearance. The aperture does notline up with the base as it does in Lepetodrilus.Gorgoleptis sp. 3 is alsoapproximately the samesize as Lepetodrilus spp.Its sculpture is muchcoarser, it has a pointat the outer edge of theaperture. The aperturedoes not line up withthe base as it does in Lepetodrilus.16


Lepetodrilus spp. Family Lepetodrilidae.GASTROPODASize: 170-180µm See also Fig. 1 in Mullineaux et al. (1996)Morphology:These are small protoconchs with fine pitted sculpture. Insome individuals the pits appear to form lines, but this isnot usually evident under the light microscope. The line ofthe aperture continues straight to the posterior edge of theshell in the apical view. There is a distinct medium-widthaperture rim visible under the compound microscope. Fivespecies of Lepetodrilus - L. cristatus, L. elevatus, L. ovalis, L.pustulosus (all described in McLean, 1988) and L. tevnianusMcLean 1993, are present at EPR 9°N. All of these specieshave protoconchs that are similar in size and shape. Under thelight microscope some individuals are nearly transparent (asshown above), while others are more opaque; it is possible thatthis is a taxonomically useful trait, but the species cannot bedistinguished morphologically at this time.Frequency:Pump EPR 1999-2000: CommonPump EPR 2004: CommonTrap 2004-2005: CommonUnknown benthic sp. Ais about 10µm smallerthan Lepetodrilus spp.and has reticulate ratherthan pitted sculpture.It tends to roll to exposethe aperture whenmoved with a probe,while Lepetodrilus is stable in the apical view.Clypeosectus delectus hascoarser sculpture thandoes Lepetodrilus spp.,and its aperture doesnot line up with thebase.Lepetodrilus-like. Thereis a group of slightlylarger protoconchs(~190-195μm) thatclosely resemblesLepetodrilus spp. Wehave termed themLepetodrilus-like. Theyhave coarser pitted sculpture than Lepetodrilusspp., and the aperture is slightly curved,sometimes appearing to come to a blunt pointin the front. They appear to lack an aperturerim.17


GASTROPODACan be confused with:Gorgoleptis emarginatusis approximatelythe same size asClypeosectus and hassimilar sculpture.The chief distinctionbetween the two generais that Gorgoleptisemarginatuss has a sharp point at the anterioredge and sides of the aperture, giving it ascalloped appearance. If these points have beenbroken off, the curved remnants of the aperturerim can give a clue to their presence.lacks an aperture rim.Gorgoleptis sp. 3 isapproximately the samesize as Clypeosectus andhas similar sculpture.Gorgoleptis sp. 3 hasa sharp point at theanterior edge of theaperture and apparentlyLepetodrilus-like. Theseare about 15-20μmlarger than Clypeosectusdelectus. Theirsculpture is somewhatfiner and does not showany lineation. UnlikeClypeosectus, theirapertures more or less line up with their bases,though the apertures themselves may be slightlycurved. They appear to lack an aperture rim.18


Clypeosectus delectus McLean, 1989. Family Lepetodrilidae.GASTROPODASize: 170-180µmMorphology:Small protoconchs with coarse pitted sculpture in closelyspaced rows, giving the effect of lineate sculpture. The apertureis slightly wavy, with a distinct medium-width rim visibleunder the compound microscope.See also Fig. 2 in Mullineaux et al. (1996), Fig. 10 inTurner et al. (1985), and p. 86 in Desbruyères et al.(2006; right photo shows the larva, left shows a juvenilewith the protoconch visible)Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: FrequentTrap EPR 2004-2005: OccasionalPointy apex is verysimilar to Clypeosectusdelectus. It is possiblethat both protoconchsrepresent differentforms of the samespecies (or possiblytwo species in the samegenus), but because of consistent differences intheir morphology, we have kept them separatefor the present. The chief differences betweenthe two groups are that the sculpture of C.delectus is coarser, the shape of the shell is morerounded and the aperture rim is wider. Theprotoconch of C. delectus is also slightly larger(175μm vs. 160μm) than pointy apex.Lepetodrilus spp. isapproximately thesame size as C. delectus.The distinguishingfeatures are that in C.delectus the line of theaperture does not lineup with the posteriorportion of the shell, whereas in Lepetodrilusit forms a nearly straight line. The sculpturein Lepetodrilus is much finer and more widelyspaced and usually doesn’t show any obviouslineation under the dissecting microscope.Unknown 5 is aboutthe same size as C.delectus, but as forLepetodrilus, theaperture and the baseform a nearly straightline. The narrowaperture rim flares outto the sides and at the outer edge. This specieshas reticulate, rather than pitted, sculpture.19


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GASTROPODAGorgoleptis emarginatus McLean, 1988. Family Lepetodrilidae.Size: 175-180µmMorphology:Gorgoleptis emarginatus is one of three presumed Gorgoleptismorphs we find in plankton samples at EPR 9°N. It has coarsepitted sculpture in rows that follow the curve of the shell. Themost distinctive feature of these protoconchs is the scallopededges of the aperture, with sharp points at the anterior edge andon either side. There is a narrow aperture rim, tapering towardthe posterior edge. The protoconch matches that of Gorgoleptisemarginatus in size and sculpture, but the scallops are notpreserved in post-larval specimens, making the identificationsomewhat tentative.See also Fig. 2 in Mullineaux et al. (1996)Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: FrequentTrap EPR 2004-2005: FrequentCan be confused with:smaller.Gorgoleptis spiralisis the most similarprotoconch to G.emarginatus. Ingeneral appearance andsculpture the two arenearly identical, but G.spiralis is about 30µmGorgoleptis sp. 3 isapproximately the samesize as G. emarginatus,with similar sculpture.It has a morepronounced point atthe outer edge of theaperture and lacks theside points. It is also much less common.Clypeosectus delectusis similar in sizeand sculpture to theGorgoleptis species. Themain difference is in theshape of the aperture:all the Gorgoleptisspecies have at least onesharp point, whereas in Clypeosectus it is nearlystraight.21


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Gorgoleptis sp. 3 Family Lepetodrilidae.GASTROPODASize: 180-185µmMorphology:This protoconch closely resembles the two Gorgoleptisprotoconchs in sculpture and is roughly the same size asGorgoleptis emarginatus. It differs from the others in havingonly a single sharp point at the anterior edge of the aperture,and the sides are sinuous rather than being scalloped. If it hasan aperture rim, it is very narrow.A third species of Gorgoleptis, Gorgoleptis patulus McLean,1988, was described from the Galápagos Rift. Its protoconch isunknown, but it could be a possible candidate for this morph.The species has not been reported from EPR 9°N.Frequency:Pump EPR 1999-2000: RarePump EPR 2004: Rare (1 individual collected off-axis)Trap EPR 2004-2005: Not collectedCan be confused with:Gorgoleptis emarginatusis nearly the same size asGorgoleptis sp. 3, beingabout 5µm smaller. Ithas points on the sidesof the aperture, whereasGorgoleptis sp. 3’saperture is only slightlywavy. Gorgoleptis emarginatus is much morecommon.Gorgoleptis spiralis isabout 35µm smallerthan Gorgoleptis sp. 3and has side points onthe aperture.Clypeosectus delectusis similar in sizeand sculpture to theGorgoleptis species. Themain difference is in theshape of the aperture:Gorgoleptis sp. 3 has asharp point at the outeredge, whereas in Clypeosectus it is nearly straight.23


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GASTROPODAUnknown 7. Family Unknown.Size: 180-190µmMorphology:This is a small protoconch with sculpture consisting of acoarse raised network of reticulate sculpture overlain by fivewidely spaced lines. These lines are difficult to see with thelight microscope, but show up clearly in the SEM. The anteriorportion of the shell is smooth. The aperture is slightly sinuousand flared at the anterior edge and it has a medium-width rim,tapering toward the posterior.Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: OccasionalTrap EPR 2004-2005: Not collectedCan be confused with:Unknown 7 is most likely to be confusedwith Unknown 9, which has a similar type ofsculpture. Unknown 9 is slightly larger andsome of its lineate sculpture extends all theway to the aperture, whereas all five lines inUnknown 7 stop well short of the aperture.Unknown 9 is also shorter in height for itsdiameter than Unknown 7. The approximateheight:diameter figures are 110:190µm for Unknown 9 and 125:180µmfor Unknown 7.Unknown 7’s sculpture and size are similarto that of Unknown 8. Unknown 8 has moreclosely spaced lines, and it is also greater inheight for its diameter than Unknown 7.The approximate height:diameter figures are135:190µm for Unknown 8 and 125:180µm forUnknown 7.25


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Lepetodrilus-like protoconchs Family ?Lepetodrilidae.GASTROPODASize: 185-200µmMorphology:Lepetodrilus-like protoconchs are quite similar in generalappearance to Lepetodrilus spp. They are slightly larger andhave coarser pitted sculpture. The aperture is slightly curvedand comes to a blunt point at the outer edge. There appears tobe no aperture rim.Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: OccasionalTrap EPR 2004-2005: OccasionalCan be confused with:These protoconchsare most likely tobe confused withLepetodrilus spp.Lepetodrilus spp. areslightly smaller (170-180µm) and have astraight aperture, whichforms a line with the base of the shell. They alsohave an aperture rim, which this group lacks.Gorgoleptis emarginatus(upper) and Gorgoleptissp. 3 (lower). Bothspecies are slightlysmaller (175-185µm)and have pittedsculpture, as doesthis species. The mostobvious difference isthat both Gorgoleptishave sharp pointsat the outer edge ofthe aperture (and G.emarginatus has scallopson the sides as well),whereas Lepetodrilus-like protoconchs have onlya blunt point on the distal edge.Clypeosectus delectus issmaller (170-180µm)and has an aperturerim. In Clypeosectus andGorgoleptis, the pittedsculpture often appearsto form lines, whichhas not been seen in theLepetodrilus-like protoconchs.27


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GASTROPODAUnknown 8. Family Unknown.Size: 190-200µmMorphology:This is a rather fragile protoconch, generally found with atleast the aperture damaged. It is very rounded in appearance,with regularly spaced lines extending about 3/4 of the way tothe aperture. There is some hint of sparse reticulate sculptureon the sides and base. The aperture is probably sinuous, andwe have seen no evidence of a rim. This protoconch resemblesseveral in the family Skeneidae; for example, see Warén andBouchet (1993; Fig. 23, A & C) for images of the protoconchsof Xyloskenea costulifera Marshall, 1988, from deep-sea woodfalls and Ventsia tricarinata Warén and Bouchet, 1993, fromthe Lau Basin.Frequency:Pump EPR 1999-2000: RarePump EPR 2004: RareTrap EPR 2004-2005: Not collectedCan be confused with:Unknown 8’s sculpture and size are similar tothat of Unknown 7. Unknown 7 has only fivelines that are more widely spaced than those onUnknown 8. It is also shorter in height for itsdiameter than Unknown 8. The approximateheight:diameter figures are 135:190µm forUnknown 8 and 125:180µm for Unknown 7.29


GASTROPODAUnknown 9. Family Unknown.Size: 190-210µmMorphology:This protoconch has a short stretch of lineate sculpture atthe axis of curvature which then spreads out into an area ofinterconnected reticulate sculpture that covers the proximal1/3 of the shell. From this point a few lines extend towardthe aperture, most stopping well short of it, but a fewreaching all the way. The aperture is roughly circular and isonly about 1/3 of the diameter of the shell. There appears tobe a narrow aperture rim, surrounded by a wider region ofstippling, possibly a continuation of the reticulate sculpture.Frequency:Pump EPR 1999-2000: Not collected on axisPump EPR 2004: RareTrap EPR 2004-2005: Not collectedCan be confused with:Unknown 9 is most likely to be confusedwith Unknown 7, which has a similar type ofsculpture. Unknown 9 is slightly larger and someof its lineate sculpture extends all the way to theaperture, whereas all five lines in Unknown 7stop well short of the aperture. Unknown 7 isgreater in height for its diameter than Unknown9. The approximate height:diameter figures are110:190µm for Unknown 9 and 125:180µm for Unknown 7.31


GASTROPODA32


Echinopelta fistulosa McLean, 1989. Family Peltospiridae.GASTROPODASize: 210-220µmMorphology:This group is quite angular in appearance and has the linesbeginning on a raised platform at the base of the shell. In thisform the lines become indistinct for most of the shell. Theaperture is slightly flared and has a narrow rim. We believethis morphotype corresponds to Echinopelta fistulosa, whichhas the same raised platform on the base (see SEM photo atright of a protoconch broken off a juvenile E. fistulosa).Frequency:Pump EPR 1999-2000: Frequent (but combined withunknown peltospirid 240µm)Pump EPR 2004: FrequentTrap EPR 2004-2005: OccasionalCan be confused with:sculpture.Lirapex granularis isapproximately 10µmlarger and lacks theraised platform atthe base. It alsohas tubercles at theposterior end inaddition to the lineatePeltospira sp. is slightlylarger and less angularin appearance thanEchinopelta. It alsodoes not have the raisedplatform at the base.Unknown peltospirid240µm is similarin outline but isapproximately 30µmlarger in diameter anddoes not have the raisedplatform at the base.33


GASTROPODACan be confused with:sculpture.Lirapex granularis isapproximately thesame size as Peltospira,but is greater in heightfor its diameter. Italso has tubercles atthe posterior end inaddition to the lineateEchinopelta fistulosais slightly smallerand more angularin appearance thanPeltospira. It also hasa raised platform at thebase where the linesbegin.Unknown peltospirid240µm is greater inheight for its diameter,which is approximately20µm larger than thatof Peltospira.34


GASTROPODAPeltospira spp. Family Peltospiridae.Size: 210-220µmMorphology:This protoconch has approximately 16-18 lines, beginning ina V at the axis of coiling and following the curvature of theshell, stopping abruptly at the same point about 2/3 of theway to the aperture. The aperture is perfectly circular whenviewed from the bottom and is surrounded by a narrow rimwhich flares out to the sides when viewed from the top. It looksmore streamlined than most peltospirids, since it is shorterfor its diameter and the base is more smoothly rounded. Itmatches the SEM of Peltospira operculata in Mullineaux et al.(1996) in size and general appearance, but is also very similarto the Nodopelta subnoda protoconch SEM in Desbruyères etal. (2006; p. 117). Molecular work is ongoing and may helpto resolve the issue. In the meantime, we have attributed thisprotoconch to Peltospira, as it is the most common genus atEPR 9°N. There are at least two species of Peltospira presentat EPR 9°N: Peltospira delicata McLean, 1989, and Peltospiraoperculata McLean, 1989. A third species, Peltospira lamelliferaWarén & Bouchet, 1989, has been described from 13°N andmay also be at 9°N.See also Fig. 3 in Mullineaux et al. (1996)Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: OccasionalTrap EPR 2004-2005: Not collected35


GASTROPODA36


GASTROPODALirapex granularis Warén & Bouchet, 1989. Family Peltospiridae.Size: 215-220µmMorphology:Lirapex has an unusual type of sculpture consisting of thelineate sculpture typical of peltospirids with numeroustubercles between them, especially near the axis of coiling. Bothfade out about halfway to the aperture. When viewed from thebottom under the light microscope, a thick bar running acrossthe shell is visible just posterior to the aperture. The aperture isnearly straight, with a wide rim tapering toward the posterior.The shell is transparent and glassy-looking.Frequency:The species was described from EPR 21°N and has beenreported from 9°N, though adults are rarely collected there.Pump EPR 1999-2000: OccasionalPump EPR 2004: OccasionalTrap EPR 2004-2005: OccasionalSee also Fig. 3 in Mullineaux et al. (1996) and p. 115in Desbruyères et al. (2006)Can be confused with:Peltospira spp. is similarin size to Lirapex.However, Peltospira ismore streamlined inappearance and doesn’thave tubercles or thebar posterior to theaperture.Echinopelta fistulosais similar in size toLirapex; however, it isabout 10µm smaller,more angular inappearance, has a raisedplatform at the base andno tubercles.Unknown peltospirid240µm closelyresembles Lirapex ingeneral morphology,but does not havetubercles and is slightlylarger.37


GASTROPODACan be confused with:Peltospira spp. is about 20µm smaller thanUnknown peltospirid 240µm and is morestreamlined in general appearance, being lessin height for its diameter.Echinopelta fistulosa is about 30µm smallerand is more angular in appearance. It also hasa raised platform at the base where the linesbegin.38


Unknown peltospirid 240µm Family ?Peltospiridae.GASTROPODASize: 230-240µmMorphology:This is another possibly heterogeneous group of protoconchs.They are slightly larger than the “Peltospira” group and aretaller for their diameter, although not as angular as Echinopeltafistulosa. The sculpture begins at the axis of curvature andcontinues about 2/3 of the way to the aperture, which isslightly flared. From below it closely resembles Peltospira sp.,though it is slightly wider for its diameter. The aperture rim issimilar in width to Lirapex granularis, wider than in the otherpeltospirid forms. It may be that the ratio of the diameter tothe height will be useful in distinguishing the forms.Frequency:Pump EPR 1999-2000: Frequent (but combined with 210μmsize class)Pump EPR 2004: FrequentTrap EPR 2004-2005: OccasionalUnknown neomphalid W is quite similar ingeneral appearance and size. The easiest way todistinguish the two is to look at the sculpture- Unknown neomphalid W has reticulatesculpture instead of lineate.Lirapex granularis is about 20µm smaller thanUnknown peltospirid 240µm and has tuberclesat the base as well as lineate sculpture.39


Unknown neomphalid B Family ?Neomphalidae.GASTROPODASize: 230-240µmMorphology:These protoconchs are moderately large and very distinctive.They have reticulate sculpture over the entire shell, more orless disorganized at the base, but becoming regularly spacedlines toward the aperture. The aperture is slightly sinuous andhas a distinct ridge above it. We have not been able to matchthem with a known vent species, but have tentatively assignedthem to Neomphalidae because of their reticulate sculptureand similarity to other neomphalids.Frequency:Pump EPR 1999-2000: RarePump EPR 2004: Not collectedTrap EPR 2004-2005: OccasionalCan be confused with:This group is most likelyto be confused with oneof the Melanodrymiaspecies which theysuperficially resemblein morphology andsize. Melanodrymiaaurantiaca has finerreticulate sculpture with no lineation and amore gradual bump above the aperture, ratherthan a raised ridge.Melanodrymia galeronaealso has finer and moreirregular reticulatesculpture and nolineation. It lacks eithera ridge or a bump abovethe aperture, which ismore sinuous than thatof Unknown neomphalid B.Unknown neomphalid290µm is about50µm larger and lacksthe ridge above theaperture. Its sculptureis similar near thebase, but does not formregular lines distally.41


GASTROPODA42


GASTROPODACyathermia naticoides Warén & Bouchet, 1989. Family Neomphalidae.Size: 230-240µmMorphology:Cyathermia naticoides has a moderately large protoconch. Theposterior is covered by coarse reticulate sculpture which givesthe appearance of bubbles under the light microscope. Theanterior portion is smooth. The aperture is slightly sinuous andthere is a medium-width rim.Frequency:Pump EPR 1999-2000: CommonPump EPR 2004: CommonTrap EPR 2004-2005: CommonCan be confused with:The protoconchs can be easily confused withthose of Neomphalus fretterae, although theadults look quite different. The chief differencesbetween the two are that Neomphalus has finerreticulate sculpture and the outer edge flaresout at the aperture. The aperture rim is widerin Neomphalus than in Cyathermia, taperingtoward the posterior edge.43


GASTROPODA44


Neomphalus fretterae McLean, 1981. Family Neomphalidae.GASTROPODASize: 240-250µmMorphology:Neomphalus fretterae has a moderately large protoconch withreticulate sculpture over the proximal half of the shell. Thedistal half is smooth, with the outer edge flaring out abovethe aperture. The aperture is sinuous and there is a wide rim,tapering toward the inner edge, which is visible under the lightmicroscope.The SEM above is Fig. 2D in Mullineaux et al. (1996),with kind permission of Springer Science and BusinessMedia.Frequency:Pump EPR 1999-2000: FrequentPump EPR 2004: FrequentTrap EPR 2004-2005: FrequentCan be confused with:The species that Neomphalus fretterae is mostlikely to be confused with is Cyathermianaticoides, as both are the same size and verysimilar in appearance. The main differences arethat Neomphalus fretterae has finer reticulatesculpture, a flare at the outer edge of theaperture and the aperture rim is about twice aswide.45


GASTROPODACan be confused with:Unknown neomphalid sp. B. This protoconchis very similar in size and general appearance.However, it has a thin ridge that parallels theaperture, forming a distinct rim. The apertureis straighter in this species and the sculptureis stronger and more regular, forming distinctrows at the anterior end of the shell.Bathymargarites symplector. This protoconchis similar in general appearance, but is muchlarger (~350μm) and lacks the overall reticulatesculpture.46


Melanodrymia ?galeronae Warén & Bouchet, 2001.Family Neomphalidae.GASTROPODASize: 240-250µmMorphology:This is a moderately large protoconch with overall finereticulate sculpture. The anterior edge flares at the aperture,which is strongly sinuous.Frequency:Pump EPR 1999-2000: RarePump EPR 2004: Not collectedTrap EPR 2004-2005: RareMelanodrymia ?galeronae is most likely to beconfused with its congener, Melanodrymiaaurantiaca. The protoconchs are very similarin size and general appearance. However, thesculpture is finer on M. ?galeronae, the apertureis less strongly sinuous and it lacks the distinctbump above the aperture.Unknown neomphalid 290μm. Thisprotoconch is very similar in general appearanceand sculpture and may well be an undescribedMelanodrymia species. It is, however, larger(290μ against 250μm) and the aperture is moredeeply sinuous, as well as flaring out more at theouter edge.47


GASTROPODA48


GASTROPODA50


GASTROPODAPachydermia laevis Warén & Bouchet, 1989. Family Neomphalidae.Size: 245-250µmMorphology:Pachydermia laevis has a moderately large protoconch withregular overall interconnected reticulate sculpture, stronglymarked in the proximal region and becoming finer and lessdistinct toward the aperture. The aperture is slightly curvedwith a thickened broad rim that tapers slightly toward theinner edge.Frequency:Pump EPR 1999-2000: FrequentPump EPR 2004: FrequentTrap EPR 2004-2005: OccasionalCan be confused with:Pachydermia laevis is most likely to be confusedwith Unknown neomphalid W, as they areapproximately the same size and both havereticulate sculpture. However, Unknownneomphalid W lacks the thickened aperturerim and its sculpture is coarser and less regularand is limited to the proximal half of the shell.51


GASTROPODA52


Eulepetopsis vitrea McLean, 1990. Family Neolepetopsidae.GASTROPODASize: 245-250µmMorphology:This is a moderately large protoconch, with shallow,coarse pitted sculpture over the entire shell, giving it agrainy appearance under the light microscope. The shell isdorsoventrally flattened, so it is usually found either with theaperture facing down or lying at an angle with the aperturevisible. The posterior portion of the aperture flares out fromthe body, forming a deep indentation on both sides. Theposterior of the shell is smoothly rounded.Frequency:Pump EPR 1999-2000: FrequentPump EPR 2004: FrequentTrap EPR 2004-2005: OccasionalCan be confused with:The only protoconch that is likely to be confusedwith Eulepetopsis vitrea in our samples is anothergenus in the same family, Neolepetopsis sp. Bothprotoconchs are about the same size and similarin appearance. However, the posterior edge ofNeolepetopsis is slightly flattened laterally, givingit a more pointed look. This is best seen whenviewed from the side. Viewed from above, theNeolepetopsis protoconch is oval, whereas thatof Eulepetopsis is indented behind the aperture.53


GASTROPODA54


Unknown neomphalid W Family Neomphalidae.GASTROPODASize: 250-260µmMorphology:This is a moderately large protoconch with coarse reticulatesculpture over the proximal half of the shell. Under thedissecting microscope the sculpture sometimes appears lineateand the general outline of the shell is typical of peltospirids,but the reticulate sculpture is easily visible under thecompound microscope. The aperture is straight and there is awide rim, tapering toward the posterior edge of the aperture,visible under the light microscope. Warén & Bouchet,1989, described a species with a very similar protoconchas Depressigyra planispira (later amended to Planorbidellaplanispira), but since later specimens of this species appear tohave a different protoconch (A. Warén, pers. comm.), we havekept our original designation.Frequency:Pump EPR 1999-2000: FrequentPump EPR 2004: FrequentTrap EPR 2004-2005: OccasionalCan be confused with:Pachydermia laevis. Unknown neomphalidW lacks the thickened aperture rim and itssculpture is coarser, less regular and limited tothe proximal portion of the shell.Unknown peltospirid 240µm is similar in sizeand shape, but has lineate sculpture, instead ofreticulate. This may not be obvious viewed fromthe side, but when viewed from the top, theedges of the lines can be seen if lineate sculptureis present.55


GASTROPODACan be confused with:Melanodrymia aurantiaca is most likely to beconfused with its congener, Melanodrymia?galeronae. The protoconchs are very similarin size and general appearance. However, thesculpture is finer on M. ?galeronae, the apertureis less deeply sinuous and it lacks the distinctbump above the aperture, instead having agentle curve which ends in a flare at the aperture.Bathymargarites symplector. This protoconchis similar in general appearance, but is muchlarger (~350μm) and lacks the overall reticulatesculpture.56


GASTROPODAMelanodrymia aurantiaca Hickman, 1984. Family Neomphalidae.Size: 250-260µmMorphology:Melanodrymia aurantiaca has a moderately large protoconchentirely covered with irregular reticulate sculpture, giving it agrainy appearance when viewed under a light microscope. Theaperture is deeply sinuous and there is a broad ridge or bumpat the anterior edge of the shell above the aperture.Frequency:Pump EPR 1999-2000: FrequentPump EPR 2004: FrequentTrap EPR 2004-2005: Occasionalshell.Unknown neomphalid sp. B. This protoconchis very similar in size and general appearance.However, instead of having a thick bump atthe anterior edge, it has a narrow ridge thatparallels the aperture, forming a distinct rim.The aperture is much straighter in this speciesand the sculpture is stronger and more regular,forming distinct rows at the anterior end of theUnknown neomphalid 290μm. Thisprotoconch is very similar in general appearanceand sculpture and may well be an undescribedMelanodrymia species. It is, however, larger(290μm against 260μm) and the aperture ismore deeply sinuous, as well as flaring out at theouter edge.57


GASTROPODACan be confused with:Melanodrymia aurantiaca is about 30µmsmaller, with finer sculpture. Its aperture ismore smoothly curved.Melanodrymia ?galeronae is about 40µm smaller,also with finer sculpture and a more smoothlycurved aperture.58


GASTROPODA60


GASTROPODARhynchopelta concentrica McLean, 1989. Family Peltospiridae.Size: 280-290µmMorphology:This is one of the few easily identified peltospirids. It is a largeprotoconch with strong lineation extending about 2/3 of theway to the aperture. Like most peltospirids, the aperture isstraight viewed from the side and flares out to the sides whenviewed from from the top. There is also an abrupt ridge oneither side of the base near the axis of coiling. The shell istransparent and robust; they are seldom found damaged.Frequency:Pump EPR 1999-2000: FrequentPump EPR 2004: FrequentTrap EPR 2004-2005: FrequentCan be confused with:Rhynchopelta is unlikely to be confused with anyother protoconch. The only other peltospiridprotoconch close to it in size, Ctenopeltaporifera (pictured at left), is quite differentmorphologically.61


GASTROPODACtenopelta porifera Warén & Bouchet, 1993. Family Peltospiridae.Size: 290-310µmMorphology:This is the largest peltospirid protoconch we have found atEPR. Lineate sculpture, narrowly spaced, covers the posteriorhalf of the protoconch. The anterior portion is smooth. Theaperture is deeply sinuous and not circular when viewed frombeneath, unlike all other peltospirids we have found.Frequency:Pump EPR 1999-2000: Not collectedPump EPR 2004: RareTrap EPR 2004-2005: RareCan be confused with:Because of its size and distinctive sculptureand morphology, this species is unlikely tobe confused with any other protoconch.Rhynchopelta concentrica (pictured at left)is nearly as large, but is quite different inappearance.63


GASTROPODA64


Bathymargarites symplector Warén & Bouchet, 1989.Family Trochidae.GASTROPODASize: 320-350µmMorphology:The shell consists of two parts, a proximal smooth portionapproximately 200μm in diameter and a distal portion withaxial striations. The aperture is curved, flares out at the anterioredge and is asymmetrical, extending farther out on the apicalside than on the basal side.See also Warén & Bouchet, 1989, Figure 10, for SEMphotos of larval and juvenile shells.Frequency:Pump EPR 1999-2000: RarePump EPR 2004: RareTrap EPR 2004-2005: FrequentCan be confused with:Bathymargarites’ larval shell is unique amongthe species at 9°N and is therefore not likelyto be confused with any other species. Ithas a superficial similarity to Melanodrymiaaurantiaca, shown at left, but the latter is muchsmaller (~260μm) and has reticulate sculptureover the entire shell.65


GASTROPODA66


GASTROPODALaeviphitus sp. Family Elachisinidae.Size: 360-400µmMorphology:Laeviphitus has a large coiled protoconch. It is presumablyplanktotrophic, with an unornamented protoconch I andprotoconch II with fine spiral ridges and strong axial ribsto form a distinctive crosshatched pattern. The species isunknown, as no adults in this genus have been collected onthe EPR, though members of the genus have been collected atvent and seep sites elsewhere.See also Mullineaux et al. (1996), Figure 5e&f, forSEM photosFrequency:Pump EPR 1999-2000: FrequentPump EPR 2004: CommonTrap EPR 2004-2005: CommonCan be confused with:There are few coiled larvae in the plankton at9°N and it is unlikely that this species wouldbe confused with any other. Phymorhynchusprotoconchs are also large and coiled, but havea taller spire and an ornamented protoconchI. The patterning on protoconch II inPhymorhynchus is diamond-shaped.67


GASTROPODA68


GASTROPODAPhymorhynchus sp.(presumably Phymorhynchus major Warén & Bouchet, 2001). Family Conidae.Size: >1mm (late-stage, left photo),240µm (PI only, right photo)Morphology:This is a large coiled larva with planktotrophic development.The sculpture of PI appears to consist of parallel spiral linesunder the light microscope, although there are short axial barson each line visible at high magnification (above, right). PIIhas regularly spaced diagonal axial ribs that cross to form adiamond-shaped pattern. Most late stage individuals appeargolden brown, as shown above left.See Gustafson and Lutz (1994) for SEM of larvacollected from an egg capsule at the GalápagosRift and Lutz et al. (1986), Fig 1C,D for SEM’s oflarval shell on juvenileFrequency:Pump EPR 1999-2000: Not collected on axisPump EPR 2004: Not collectedTrap EPR 2004-2005: Not collectedCan be confused with:smaller (400µm).The larva of Phymorhynchus major is unlikely tobe confused with any other species, as there areso few coiled larvae at 9°N and its sculpture is sodistinctive. Laeviphitus also shows cross-hatchedsculpture on PII, but in that case the lines formrectangles rather than diamonds and the spire ismuch flatter. It is also generally white and much69


BIVALVIA70


BIVALVIABathymodiolus thermophilus Kenk & Wilson, 1985.Family Mytilidae.Size: 400-450µmMorphology:Bathymodiolus thermophilus have planktotrophic larvae.We find them in our plankton samples when they are closeto settling. It is possible that we do not collect them astrochophores or D-stage larvae because they may be too smallto be caught on our 63µm sieves. Near to settlement they arebrownish in color.Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: RareTrap EPR 2004-2005: Not collectedCan be confused with:Bathymodiolus thermophilus is similar in color tojuvenile Bathypecten, but is much smaller (< 450µm vs. >1mm) and not scallop-shaped.71


BIVALVIA72


Bathypecten vulcani Schein-Fatton, 1985. Family Pectinidae.BIVALVIASize: 840µm (larva, above left), >1mm (juvenile)Morphology:Shell thin, fragile, transparent to translucent. Most of theindividuals we collect are larger than 2mm and possess thetypical scallop morphology of the specimen on the right. Thesewould presumably be swimming juveniles rather than larvae.The smaller specimen (above, left) is the only larva we’vecollected to date. Desbruyères et al. (2006) describe the speciesas having non-planktotrophic larval development.Frequency:Pump EPR 1999-2000: Not collectedPump EPR 2004: Not collectedTrap EPR 2004-2005: Not collectedCan be confused with:Bathymodiolus thermophilus is similar in color tojuvenile Bathypecten, but is much smaller (< 450µm vs >1mm) and not scallop-shaped.73


POLYCHAETA74


POLYCHAETAAmphisamytha galapagensis Zottoli, 1983. Family Ampharetidae.Size: 280-500µmMorphology:Smallest individuals (3-4 chaetigers) have neither appendagesnor distinctive morphology, as shown above left. At around400µm and 5-6 chaetigers they develop a pair of smooth gillsbehind the prostomium (shown above in right photo); theadults will ultimately have four pairs, but the remaining threepairs appear much later in development. Since the smallestlarvae are so featureless, it is possible that there may be morethan one species represented.Frequency:Pump EPR 1999-2000: Not distinguishedfrom other polychaete larvaePump EPR 2004: Not collectedCan be confused with:The smallest Amphisamytha larvae fall in the sizerange of the nectochaetes. Nectochaete larvaehave a ciliary band circling the body near theanterior end (at right in photo) and are generallythinner for their length than Amphisamytha.Ophryotrocha larvae are similar in size andgeneral outline to Amphisamytha, but havea prominent jaw apparatus visible throughthe body wall. Their parapodia are also moreprominent than those of Amphisamytha.75


POLYCHAETA76


POLYCHAETA78


POLYCHAETA“Chaetosphaerids” Unknown families.Size: Regular type: 280-400µm,Spiny type: 200-320µmMorphology:We have been referring to these larvae as “chaetosphaerids”because many of them bear a superficial resemblance to somespionid larvae. However, we do not believe that they arenecessarily spionids, nor that they are a homogeneous group.These larvae are common enough that it seems likely that theyare vent species. Nonetheless, we have not been able to matchthem up with any known species, as they do not resemble theyoung juveniles of any polychaete we have seen. Attemptsto resolve the identification using molecular methods areongoing.Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: Common79


POLYCHAETA80


POLYCHAETAGlycera sp. Family Glyceridae.Size: ~600-700µm, dependingon number of chaetigersMorphology:These larvae have long parapodia, usually angled toward theposterior of the body. The head is blunt and conical, with a darkpigmented collar around it, and there are four small antennaewhich form a cross at the tip of the prostomium, though theseare not always visible. Small jaws can usually be seen throughthe body wall. We have found glycerid polychaetes (Glycerasp.) on settlement blocks around the periphery of the 9°Nvents. These larvae may be that species or possibly anothernon-vent species.Frequency:Pump EPR 1999-2000: Not collected on axisPump EPR 2004: FrequentCan be confused with:Glycera sp. is most likely to be confused withOphryotrocha sp., since both species have visiblejaws. However, the shape of the jaws is quitedifferent and we generally find Ophryotrochaas 2-3 chaetiger larvae (~ 280 - 350μm), whileGlycera is usually much larger (~7-9 chaetigers,~ 600 - 700μm)81


POLYCHAETA82


POLYCHAETANectochaetes Unknown families.Size: 170-380µmMorphology:Nectochaetes of several varieties are often present in ourplankton samples. They have a blunt, bulbous prostomiumwith a ciliary collar surrounding the body. They are relativelythin for their length and their chaetae, usually at least aslong as the body is wide, are angled toward the posterior.Preliminary molecular analyses indicate that more than onefamily is represented in this group.Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: CommonCan be confused with:The smallest Amphisamytha larvae fall in thesize range of the nectochaetes and have a similarnumber of chaetigers. Nectochaete larvae have aciliary band behind the head and are generallythinner for their length than Amphisamytha.83


POLYCHAETA84


Nereis sp., possibly Nereis sandersi Blake 1985. Family Nereididae.POLYCHAETASize: ~300-450µm, dependingon number of chaetigersMorphology:Nereidid larvae are usually found at the 3-4 chaetiger stage inour samples. They have visible antennae and tentacular cirriprojecting from the sides of the head, as well as a pair of analcirri. The parapodia are well-developed and there are usuallydark or reddish spots visible at the bases of two adjacent pairs,as shown above. This is presumably Nereis sandersi Blake, theonly nereidid at 9°N.Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: FrequentCan be confused with:These larvae are most likely to be confused withOphryotrocha sp., which is superficially similar,but lacks the tentacular cirri and the dark spotson the parapodia. Nereis has larger parapodiawith longer chaetae, but lacks the obvious jawapparatus that Ophryotrocha has.85


POLYCHAETACan be confused with:This group is most likely to be confused withNereis sp. It can be quickly distinguishedby its easily visible jaws and by the fact thatNereis larvae have four dark or reddish dots atthe base of two adjacent pairs of parapodia.Nereis also has obvious antennae and tentacularcirri projecting from the sides of the head andis generally somewhat larger (300-450µm;individual at left is 400µm).It is possible that Ophryotrocha might bemistaken for a small Glycera sp., as both specieshave visible jaws. However, the shape of thejaws is quite different and Glycera has fourantennae in the form of a cross at the tip ofits prostomium. We generally find Glycera sp.when it is much larger - ~ 600 - 700μm - andwith more chaetigers.86


Ophryotrocha sp., possibly Ophryotrocha akessoni Blake, 1985.Family Dorvilleidae.POLYCHAETASize: 280µm at 2 chaetigersMorphology:We have attributed these larvae to Ophryotrocha, based on theirgeneral appearance, especially the jaw apparatus, which canbe seen clearly through the body wall. They have prominentparapodia that stick out to the sides and two anal cirri areusually visible at the posterior end. The adults possess twoantennae toward the front of the prostomium and two lateralpalps anterior to the jaws; these are sometimes visible in thelarvae, but often are indistinct.Frequency:Pump EPR 1999-2000: Not distinguishedfrom other polychaete larvaePump EPR 2004: CommonAmphisamytha larvae are approximately thesame size as Ophryotrocha, but lack jaws andobvious parapodia.Unknown polychaete A is similar in generaloutline to Ophryotrocha, but is smaller (thisindividual is 200µm), yellower in color and lacksthe jaw apparatus. In this group, the chaetae areangled toward the posterior rather than stickingout to the sides.87


POLYCHAETA88


POLYCHAETAPolynoids Family Polynoidae.Size: 190µm (left) to >1mmMorphology:There are many species of polynoids at the 9°N vents and wehave not attempted to assign any of the forms we find in theplankton samples to species. Most of the morphotypes wecollect are actually juveniles; it is not uncommon for polynoidsto metamorphose in the plankton and live there for extendedperiods before settlement (Young et al., 2001, p.211). They arecharacterized by having long parapodia and chaetae and largeblunt heads with various appendages. They may retain theirscales, but these are easily lost.Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: Frequent89


POLYCHAETAUnknown polychaete A, Unknown Family.Photo by S. MillsSize: ~200µmMorphology:Small nectochaete larva, generally found at the two-chaetigerstage. Chaetae about as long as the body is wide, angled towardthe posterior end. No prostomial appendages or jaws. Thisgroup has been present in sampling prior to the 2005-2006eruptions at 9°N, EPR, but was not distinguished from otherunknown polychaetes. It may be a smaller version of a memberof our nectochaete group, but because of consistent differencesin morphology and color, we have listed it separately.Frequency:Pump EPR 1999-2000: Not distinguishedfrom other polychaete larvaePump EPR 2004: Not distinguishedfrom other polychaete larvaeCan be confused with:Ophryotrocha sp. is similar in general outline,but is larger (this two-chaetiger specimen is280µm). In Ophryotrocha the parapodia stickstraight out to the sides rather than beingangled back to the posterior and it also has ajaw apparatus visible through the body wall.Unknown polychaete A tends to be yellow ortan in color when preserved in ethanol rather than gray to white likeOphryotrocha.91


POLYCHAETA92


POLYCHAETAUnknown polychaete B, Unknown Family.Size: 535µm (left), 340µm (right)Morphology:Oval-shaped larva, quite wide for its length. No chaetaevisible, but four evenly spaced ciliary bands encircle the bodyand there appear to be patches of cilia on the anterior andposterior ends. In larger individuals, jaws can be seen throughthe body wall, as in the specimen on the left. This form wasnot collected prior to the 2005-2006 eruptions at 9°N, EPRand we do not know if it belongs to the vent fauna.Frequency:Pump EPR 1999-2000: Not collectedPump EPR 2004: Not collectedCan be confused with:Archinome rosacea is similar in size and generaloutline; however, it has long, delicate chaetae,whereas Unknown polychaete B has onlycilia. Archinome has dark pigmentation on itsprostomium, but does not have a jaw apparatus.93


CRUSTACEA94


BIVALVESCRUSTACEABarnacle cyprids, Order Cirripedia.Size: various from ~600µm to >1mmMorphology:We have found a variety of cyprids in our plankton samples,most (and perhaps all) non-vent. The only vent species at 9°Nis Neolepas zevinae Newman, 1979; nothing is known aboutits larval life, but a few newly settled cyprids, approximately800µm in length, were recovered on our settlement blocks(Mullineaux et al., 2003) which presumably belong to thisspecies. Two of these are pictured above (right photo).Frequency:Pump EPR 1999-2000: RarePump EPR 2004: OccasionalTrap EPR 2004-2005: Occasional95


CRUSTACEA96


BIVALVESCRUSTACEABythograea microps de Saint Laurent, 1984.Infraorder Brachyura, Family Bythograeidae.Size: megalopa ~3mmMorphology:This is a small megalopa with long eyestalks. It has beenattributed to B. microps by de Saint Laurent (1988), whooriginally described the species and recent molecular workhas confirmed the identification (L. Hurtado, personalcommunication).Frequency:Pump EPR 1999-2000: Not collectedPump EPR 2004: Not collectedTrap EPR 2004-2005: OccasionalCan be confused with:We have only collected two types of megalopaeat this site, this one and a much larger one whichhas been attributed to Bythograea thermydron(on the left). The size difference should besufficient to distinguish the two species.97


CRUSTACEA98


BIVALVESCRUSTACEABythograea thermydron Williams, 1980.Infraorder Brachyura, Family Bythograeidae.Photo by S. MillsSize: megalopa ~8mm, zoea ~1.5mm (right)Morphology:Typical brachyuran megalopa, reddish in life, but generallytan to whitish in preservative. The zoea is similar to thosecollected from B. thermydron females (A. Dittel, personalcommunication) and we believe it also belongs to this species.Frequency:Pump EPR 1999-2000: RarePump EPR 2004: RareTrap EPR 2004-2005: OccasionalCan be confused with:We have only collected two types of megalopaeat this site, this one and a much smaller onewhich has been attributed to Bythograeamicrops. The size difference should be sufficientto distinguish the two species99


FORAMINIFERA100


FORAMINIFERA?Tretomphalus sp. Class Foraminifera.Size: ~250-300µm in diameterMorphology:Roughly spherical foraminiferan with coarse perforations onthe ventral surface (above right). The dorsal surface is composedof a brownish spiral of increasing sized flat chambers; thewhole specimen appears to be a benthic foraminiferan with aninflated chamber (similar to those in planktonic species) on theventral side. Our specimens have been examined by an expert(S. Richardson) and appear similar to the dispersal form ofthe genus Tretomphalus, a shallow-water benthic group. Most,though not all, are empty shells.Frequency:Pump EPR 1999-2000: OccasionalPump EPR 2004: Not collectedTrap EPR 2004-2005: Not collectedCan be confused with:At first glance Tretomphalus might be mistakenfor a chamber of a planktonic foraminiferan,such as is shown at left, but these do not havethe flat-chambered spiral shown above left.101


Literature CitedAdams, D.K., 2007, Influence of hydrodynamics onthe larval supply to hydrothermal vents on the EastPacific Rise. PhD Thesis, MIT, Cambridge, MA &Woods Hole Oceanographic Institution, Woods Hole,MA.Adams, D.K. & L.S. Mullineaux, 2008, Supply of gastropodlarvae to hydrothermal vents reflects transportfrom local larval sources. Limnol. Oceanogr. 53: 1945-1955.Beaulieu, S.E., L.S. Mullineaux, D.K. Adams & S.W.Mills, 2009, Comparison of a sediment trap and planktonpump for time-series sampling of larvae near deepseahydrothermal vents. Limnol. Oceanogr.: Methods7: 235-248.Blake, J.A., 1985, Polychaeta from the vicinity of deepseageothermal vents in the Eastern Pacific. I. Euphrosinidae,Phyllodocidae, Hesionidae, Nereididae, Glyceridae,Dorvilleidae, Orbiniidae and Maldanidae. Proc.Biol. Soc. Wash. 6: 67-102.de Saint Laurent, M., 1984, Crustacés décapodees d’unsite hydrothermal actif de la dorsale du Pacifique oriental(13° N) en provenance de la campagne françaiseBiocyatherm, C. R. Acad. Sci. Paris, Sér III, 299: 355-360.de Saint Laurent, M., 1988, Les mégalopes et jeunesstades crabe de trois espèces du genre Bythograea Williams,1980 (Crustacea Decapoda Brachyura). Oceanol.Acta Hydrothermalism, Biology and EcologySymposium, Paris, 4-7 November 1985, Proceedings,99-107.Desbruyères, D., M. Segonzac & M. Bright, eds., 2006,Handbook of Deep-Sea Hydrothermal Vent Fauna.Second completely revised edition. Denisia 18: 544 pp.Geiger, D.L., B.A. Marshll, W.F. Ponder, T. Sasaki &A. Warén, 2007, Techniques for collecting, handling,preparing, storing and examining small molluscanspecimens. Molluscan Res. 27: 1-50.Gustafson, R.G. and R.A. Lutz, 1994, Molluscan lifehistory traits and deep-sea hydrothermal vents and coldmethane/sulphide seeps. Pp. 76-97 in C.M. Young andK.J. Eckelbarger (eds.), Reproduction, Larval Biology,and Recruitment of the Deep-Sea Benthos. ColumbiaUniversity Press, New York.Hickman, C.S., 1984, A new archaeogastropod (Rhipidoglossa,Trochacea) from hydrothermal vents on theEast Pacific Rise. Zool Scr. 13: 19-25.Kenk, V.C. & B.R. Wilson, 1985, A new mussel (Bivalvia,Mytilidae) from hydrothermal vents in theGalapagos Rift Zone. Malacologia 26: 253-271.Kim, S.L. & L.S. Mullineaux, 1998, Distribution andnear-bottom transport of larvae and other plankton athydrothermal vents. Deep-Sea Res. II 45: 423-440.Lutz, R.A., D. Jablonski & R.D. Turner, 1984, Larvaldevelopment and dispersal at deep-sea hydrothermalvents. Science 226: 1451-1454.Lutz, R.A., P. Bouchet, D. Jablonski, R.D. Turner &A. Warén, 1986, Larval ecology of mollusks at deep-seahydrothermal vents. Am. Malacol. Bull. 4: 49-54.McLean, J.H., 1981, The Galapagos Rift limpet Neomphalus:relevance to understanding the evolution of amajor Paleozoic-Mesozoic radiation. Malacologia 21:291-336.McLean, J.H., 1988, New archaeogastropod limpetsfrom hydrothermal vents: Superfamily Lepetodrilacea.I. Systematic descriptions. Phil. Trans. Royal Soc. LondonB319: 1-32.McLean, J.H., 1989, New slit limpets (Scissurellaceaand Fissurellacea) from hydrothermal vents. Part1. Systematic descriptions and comparisons based onshell and radular characters. Contributions in Science,Los Angeles County Museum of Natural History 407:1-29.McLean, J.H., 1989, New archaeogastropod limpetsfrom hydrothermal vents: new family Peltospiridae,new superfamily Peltospiracea. Zool. Scr. 18: 49-66.McLean, J.H., 1990, Neolepetopsidae, a new docoglossatelimpet family from hydrothermal vents and itsrelevance to patellogastropod evolution. J. Zool., Lon-102


Literature Citeddon 222: 485-528.McLean, J.H., 1990, A new genus and species of neomphalidlimpet from the Mariana vents with a reviewof current understanding of the relationships amongNeomphalacea and Peltospiracea. Nautilus 104: 77-86.McLean, J.H., 1993, New species and records of Lepetodrilus(Vetigastropoda: Lepetodrilidae) from hydrothermalvents. Veliger 36: 27-35.Mullineaux, L.S., S.L. Kim, A. Pooley and R.A. Lutz,1996, Identification of archaeogastropod larvae from ahydrothermal vent community. Mar. Biol. 124: 551-560.Mullineaux, L.S., Peterson, C.H., Micheli, F. & S.W.Mills, 2003, Successional mechanism varies along agradient in hydrothermal fluid flux at deep-sea vents.Ecol. Monogr. 73: 523-542.Mullineaux, L.S., S.W. Mills, A.K. Sweetman, A.H.Beaudreau, A. Metaxas & H.L. Hunt, 2005, Vertical,lateral and temporal structure in larval distributions athydrothermal vents. Mar. Ecol. Prog. Ser. 293: 1-16.genera and a new family of gastropods from hydrothermalvents and hydrocarbon seeps. Zool. Scr. 22: 1-90.Warén, A. & P. Bouchet, 2001, Gastropoda and Monoplacophorafrom hydrothermal vents and seeps; newtaxa and records. Veliger 44: 116-231.Williams, A.B., 1980, A new crab family from the vicinityof submarine thermal vents on the GalapagosRift (Crustacea : Decapoda : Brachyura), ContributionNo. 5 of the Galapagos Rift Biology Expedition. Proc.Biol. Soc. Wash. 93: 443-472.Young, C.M., M.A. Sewell & M.E. Rice, 2001, Atlas ofMarine Invertebrate Larvae. Academic Press, San Diego,630 pp.Zottoli, R., 1983, Amphisamytha galapagensis, a newspecies of ampharetid polychaete from the vicinity ofabyssal hydrothermal vents in the Galapagos Rift, andthe role of this species in rift ecosystems. Proc. Biol.Soc. Wash. 96: 379-391.Newman, W.A., 1979, A new scalpellid (Cirripedia):a Mesozoic relic living near an abyssal hydrothermalspring. Trans. San Diego Soc. Nat. Hist., 19: 153-167.Pradillon, F., A. Schmidt, J. Peplies & N. Dubilier,2007, Species identification of marine invertebrate earlystages by whole-larvae in situ hybridisation of 18Sribosomal RNA. Mar. Ecol. Prog. Ser. 333: 103-116.Schein-Fatton, 1985, Découverte sur la ride du Pacifiqueoriental à 13°N d’un Pectinidae (Bivalvia, Pteromorpha)d’affinitiés paléozoïques. C.R. Acad. Sci. (Paris),Série III 301: 491-496.Turner, R.D., R.A. Lutz & D. Jablonski, 1985, Modesof molluscan development at deep-sea hydrothermalvents. Bull. Biol. Soc. Wash. 6: 167-184.Warén, A. & P. Bouchet, 1989, New gastropods fromEast Pacific hydrothermal vents. Zool. Scr. 18: 67-102.Warén, A. & P. Bouchet, 1993, New records, species,103


Taxonomic IndexBivalviaBathymodiolus thermophilus 71Bathypecten vulcani 73CrustaceaBarnacle cyprids 95Bythograea microps 97Bythograea thermydron 99Foraminifera?Tretomphalus sp. 101GastropodaBathymargarites symplector 65Clypeosectus delectus 19Ctenopelta porifera 63Cyathermia naticoides 43Echinopelta fistulosa 33Eulepetopsis vitrea 53Gorgoleptis emarginatus 21Gorgoleptis sp. 3 23Gorgoleptis spiralis 9Laeviphitus sp. 67Lepetodrilus-like protoconchs 27Lepetodrilus spp. 17Lirapex granularis 37Melanodrymia aurantiaca 57Melanodrymia ?galeronae 47Neolepetopsis spp. 49Neomphalus fretterae 45Pachydermia laevis 51Peltospira spp. 35Phymorhynchus sp. 69Pointy apex 11Rhynchopelta concentrica 61Unknown 7 25Unknown 8 29Unknown 9 31Unknown benthic sp. A 13Unknown neomphalid 5 15Unknown ?neomphalid 290μm 59Unknown neomphalid B 41Unknown neomphalid W 55Unknown peltospirid 240µm 39PolychaetaAmphisamytha galapagensis 75Archinome rosacea 77Chaetosphaerids 79Glycera sp. 81Nectochaetes 83Nereis sp. 85Ophryotrocha sp. 87Polynoids 89Unknown polychaete A 91Unknown polychaete B 93104


50272-101REPORT DOCUMENTATIONPAGE4. Title and Subtitle1. REPORT NO.WHOI-2009-052. 3. Recipient's Accession No.5. Report DatePhotographic identification guide to larvae at hydrothermal vents June 20096.7. Author(s)Susan W. Mills, Stace E. Beaulieu and Lauren S. Mullineaux9. Performing Organization Name and AddressWoods Hole Oceanographic InstitutionWoods Hole, Massachusetts 0254312. Sponsoring Organization Name and AddressNational Science Foundation8. Performing Organization Rept. No.10. Project/Task/Work Unit No.11. Contract(C) or Grant(G) No.(C)(G)OCE-9619605; OCE-9712233OCE-042459313. Type of Report & Period CoveredTechnical Report14.15. Supplementary NotesThis report should be cited as: Woods Hole Oceanog. Inst. Tech. Rept., WHOI-2009-05.16. Abstract (Limit: 200 words)The purpose of this guide is to assist researchers in the identification of larvae of benthic invertebrates at hydrothermal vents. Our work is basedon plankton sampling at the East Pacific Rise (EPR) 9-10˚N vent field from 1991–present. We have included frequency data from large-volumeplankton pump samples taken between 1999 and 2004 and time-series sediment trap samples from 2004-2005. The guide includes an "Introductionand Methods" section that details larval collection techniques, a "Terminology" section for gastropod and polychaete larvae, and "Literature Cited"for descriptions of species. Gastropod larvae are sorted by size and other larvae are sorted alphabetically within their taxonomic class. Each speciesinformation page also includes images of species that are similar in appearance. While our sampling was limited to EPR 9-10˚N, the guide is usefulto researchers working in other areas, since some species range from 21˚N to the southern EPR, and some have congeners in other chemosyntheticenvironments, e.g., Lepetodrilus (Juan de Fuca Ridge, Mid-Atlantic Ridge, wood falls), and Bathymodiolus (Mid-Atlantic Ridge, seeps). We wouldlike to expand the guide by including additional species from other areas and welcome contributions from other researchers. This guide is alsoavailable online at http://www.whoi.edu/vent-larval-id.17. Document Analysis a. Descriptorslarval identificationhydrothermal ventsEast Pacific Riseb. Identifiers/Open-Ended Termsc. COSATI Field/Group18. Availability StatementApproved for public release; distribution unlimited.19. Security Class (This Report)UNCLASSIFIED20. Security Class (This Page)21. No. of Pages22. Price108(See ANSI-Z39.18)See Instructions on ReverseOPTIONAL FORM 272 (4-77)(Formerly NTIS-35)Department of Commerce

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