A. Wakefield& T. McCleery NOVAPEX 6(1-2): 19-30, 10 mars 2005 Three new species of Cystiscus Stimpson, 1865 (Gastropoda: Cystiscidae) from the Tuamotu Archipelago Andrew WAKEFIELD 14 Forest Side, Buckhurst Hill, Essex, IG9 SSL, U.K. Tony McCLEERY The Moat House, Fort Road, St Peter Port, Guemsey, GYl IZU, CL KEYWORDS. Cystiscidae, Cystiscus, Tuamotu Archipelago, new species. ABSTRACT. Three new species oîCystiscus (Stimpson, 1865) are described from upper reefsubstrates ofthe C C Tuamotu's. Thèse are Cystiscus carinifern. sp., mosaican. sp. and nebulosa n. sp., and their study is based upon the material and data accumulated during two private expéditions to the région undertaken by the second author in 2001 and 2003. Information on the variability of the animal and radula ofeach species within their respective populations, and discussion ofmicrohabitats and other field observations are provided. Thèse are the first records ofthe group Chthe/Cystiscus from this part ofFrench Polynesia. and the likelihood ofthe existence ofmore species in the région is considered to be high since it is generally accepted that the diversity ofthe group is underestimated in most locations. It is considered that similarities in pattems ofanimal chromatism, shel! morphology, and radular morphometry show potential for enabling similar species within the group Crithe/Cystiscus to be associated together into subgroups. However, the overall taxonomic reorganisation and subdivision ofthe gênera Crithe and Cystiscus at this time is considered to be prématuré and too problematic given the current poorunderstanding ofthe extent of theirglobal diversity and variability. INTRODUCTION three new species each hâve a Cystiscus type radula, Two récent (2001 & 2003) private expéditions to we hâve taxonomically assigned them to the genus Cystiscus. French Polynesia by the second authorhâve provided Whether taxonomic subdivision is appropriate for an opportunity for sampling upper reefsubstrates for this shell morph type awaits further research into the micromolluscs, and in particular hâve enabled detailed study ofthe members ofthe cystiscid genus total diversity of the group, but what is becoming clear is that the division of the two gênera on the Cystiscus (Stimpson, 1865) that are found there. From a total of four new species discovered, this basis of shell morphology alone is too simplistic an paper focuses upon three closely related species from approach, and it seems more likely that a combination of radular type, shell morphology and the Tuamotu Archipelago (the fourth species animal chromatism will eventually play a rôle in discovered is a black and yellow banded species species group définitions. which is presently understudy by us). Historically the worker most often associated with Coovert (1989) reviewed the radula of Cystiscus this région is William H. Pease (1824-1871), who capensis Stimpson, 1865, the South African type described many shells from the Tuamotu's, but none species ofthe genus, along with three others and later (Coovert & Coovert, 1995) also examined radula from the group under discussion. Bavay (1922) SEMs ofa further eight Australian species including became the first and only author of a French C Polynesian représentative of the family, Marginella angasi (Crosse, 1870), the type species of Euliginella (Laseron, 1957). Coovert & Coovert (Volvaria) micros, with a type locality of the came to the conclusion that ail of thèse species are Tuamotu's. Its correct generic assignment is unclear since the type material is not présent in the Bavay congeneric based on similar radulae and shell MNHN collection in the (F. Boyer pers. comm.), and features. The shells of the new species described herein do not exhibit the obovate morphology of C. ritécweanst neoxtplfooruantdionats thbeytytphee lsoceaclointydduarutihnogr.the tWweo capensis having instead a shell morphology more like provisionally consider this species to be a that of the genus Crithe (Gould, 1860) in that the Plesiocystiscus (Coovert & Coovert, 1995) with columellar plications are excavated, an associated référence to its original figure and description, and pariétal callus ridge is présent and the shell has an we considerthat no furtherréférence to this species is overall subtriangular shape. Coovert and Coovert necessary hère. (1995, p. 70) hâve stated that 'the radulae of Crithe Many new species of Cystiscus were recently are diagnostic'. Since our own radular studies also presented in a wide ranging review of New indicate that the radulae ofboth Cystiscus and Crithe Caledonian Cystiscidae by Boyer (2003). Two ofthe appearto be quite distinct from each other, and as our species presented by Boyer, namely C. goubini 19 A. WAKLFIil 1)& T. MCCLEERY Three new species of(y.s7/.v(7/.v (Biuay, 1922) aiul C. /nin/iis (Boyer. 2003) sliarc solution and were subsequently mounted for similar shell morphology and animal palicrn scanning électron microscopy and compound light characteristics wilh two of our new species, C. microscopy. Thc radulae were assessed for number mosuiiii and C. iwhiilosa and llicsc arc comnicnted of plates, number of cusps pcr plate, pitch (distance . upon in thc discussion al the end ollliis papci. bctween successive plates) and the widtii of the The Hauaiian Cystisciis liiiiui (Kay, 1979) aiso plates. appears to be close to our new species. It is Ail shells referred to in the text are live taken adult approximalcK the same size and is morphologically spécimens unless specified otherwisc. very similar. Coovert (1987) described its columella as having three excavated plications and an Abbreviations associated pariétal callus ridgc and lie also MNHN: Muséum national d'Histoire naturelle, Paris, demonstrated the radula as ha\ing 10 cusps pcr plate France. arranged asymmctrically about a large central cusp. AWC: Andrew Wakefield Collection. lurther anatomical détails of" the animal of C. hiinci TMC: Tony McCleery Collection. are unrcportcd and therefore it cannot bc furthcr compared with thc animais ofour new species. The SYSTEMATICS new species herein described as having Cystiscid Type 3 animais (after Coovert. 1995) are Family CYSTISCIDAE Stimpson, 1865 characterized by an elongate head that has a Subfamily CYSTISCINAE Stimpson, 1865 longitudinal dorsal split with its anterior end Genus Cystiscus Stimpson, 1865 bifurcate, and may either represent ventrally fused Type species Cystiscus capensis Stimpson, 1865 (non tentacles with an associated longitudinal dorsomedial Marginclla capensis Krauss, 1848) = Marginella channel or a longitudinally split head completely cystiscus Redfield, 1870 (nom. nov.) lacking tentacles. The former interprétation is used provisionally in this study, since a détermination on Cystiscus carinifer n. sp. this issue will require detailed anatomical study. Figs 1-10,21-24,36-44 Materials and Methods Type material. Tuamotu Archipelago, Tahanea, holotype (1.56x1.05 mm) MNHN. (Figs 21-23). AU live spécimens were obtained by breaking apart Tuamotu Archipelago, Tahanea, 2 paratypes (1.43 x friable dead coral lumps into a bowl and waiting for 1.07 mm (Fig 24), 1.52x1.07 mm), MNHN. the animais to crawl out ofthe resulting grit and up Tuamotu Archipelago, Tahanea, 2 paratypes (1.43 x the side of the bowl. The coral lumps were taken 1.02 mm, 1.49 x 1.01 mm), TMC. from <1 to 7 mètres by wading, snorkelling or scuba Tuamotu Archipelago, Tahanea, 4 paratypes (1.47 x diving. 1.10 mm, 1.49 x 1.09 mm, 1.58 x 1.12 mm, 1.50 x On the first expédition, photographs were taken of 1.08 mm), AWC. the living animais shortly after collection by the second author. using a Kodak DCS 410 digital single Other material examined. Tuamotu Archipelago, lens reflex caméra with a 60mm Nikkor 1:2.8 D Tahanea, near West Pass, 2 spécimens in alcohol, macro lens. extension tubes and ring flash. On the AWC; 43 spécimens, TMC; Makemo, 6 spécimens, second expédition in 2003, the live animal images TMC. were taken using a Kodak DCS 760 caméra, mounted on an Olympus SZX12 stereo microscope over an Type Locality. Tahanea, Tuamotu archipelago. aquarium measuring 50mm x 75mm and filled to a depth of10mm, with the same caméra mounted on an Distribution. Tahanea, and Makemo Atolls, Olympus CX41 compound microscope with a xlOO Tuamotu Archipelago. PlanApo, oil-immersed lens for the radular images. The radulae were extracted from spécimens Habitat. From <1 to 7 mètres in the interstices of preserved in denaturalised alcohol using KOH dead coral lumps, frompass reefareas. Figures 1-10 Cystiscus carinifern.sp. 1-2. Détail ofhead anatomy of2 spécimens from Tahanea. 3-6. Tahanea, Tuamotu's, 3-7 m in dead coral, 4 spécimens, length 1.43-1.52 mm. 7-10.Makemo, Tuamotu's, 1-2 mètres in dead coral, 4 spécimens, length 1.43-1.50 mm. 20 A. Wakefield& T. McCleery NOVAPEX 6(1-2): 19-30, 10 mars 2005 A W \KEFIELD& T. McCLEERY Threc ncw species ofCy.s7/.v(7/.s Description. Shell small. of two whorls (inclutlinu anteriorly. Head with a pair of opaque white lines, IUlclcll^). transparent, siiiooth, glossy, triangiilar, mcdial to eyes. one extending into each tentacle its moderately roimdcd shoiilder, spire low, apical callus full length. Internai mantle dark reddish brown absent. Apertiire fairly parallel for posterior lialltlien superimposed with large creamy white blotches v\idening anteriorly. Lip smootli, lliickencd rt)Lighly concentrated into spiral zones at the shoulder posleriorly, with a thin external varix or beading in and midbody, with a dorsal extension from the latler mature spécimens. Posterior edge of lip sweeps in an anterior direction. Creamy white markings in anteriorU then back posteriorly to insert at levé! of Makemo population appear more circular and distinct suture. Distinct bulge in posterior half of last adiilt than those of the Tahanea population but the whori just before lip recurvature. Marked pariétal organisation of the pattern remains constant. Spire callus exiending full length of aperture. including also mottled cream and reddish brown. External plications. Four strong coliimellar plications. manlle translucent with yellow tint. Foot translucent occupyingjust less than 50"» ofapertural lenglli. except for fringe of opaque white, and an opaque First plication strongly émergent, joining up white zone occupying its central third. running externalK with anterior end oflabial \arix. Plications longitudinally down the midline. exca\ated inside aperture. Plications square in cross Radula: SEM examination ofa radula from an adult section, becoming more rt^undcd aller llie excavated spécimen from the type locality (Figs 36-38); area as they enter within aperture. Columella weakly cystiscid type 2 radula. 260 'V shaped rachidian lirate in some spécimens. Thin callus vvash from plates, 9)am in width, variable cusp count per plate of second columellar plication passing round body 7-9 cusps, most plates bearing a central cusp with 3 whor'-to anteriorextremity. latéral cusps on either side. Occasional plates bearing Paratypes and other material examined similar in ail a very small extra cusp between the central cusp and respects to holotype. Adult shell size range min. 1.4 x first latéral, on one or both sides ofthe central cusp mm I.Omm. max. 1.6 x 1.15 (holotype 1.56 x 1.05 (Figs 41, 42). mm). An examination of eight radulae from spécimens Animal: based on a study of several animais from from Tahanea and Makemo was performed with the Tahanea and Makemo, Type 3 animal (Figs 1-10). compound microscope. The results are summarised Tentacles short, fine, situated at anterior position on in table 1. Thèse show a cystiscid type 2 radula, 225- head. Head split longitudinally along superior aspect. 262 plates, each bearing 7 cusps. The pitch of the Lower anterior border ciliated. Eyes small, red, set plates varied from 2.43 to 2.86 [im and the ribbon well back from tentacles within latéral bulges on was 7.6 to 10 |im in width. An example of one of head. Foot halfwidth ofshell. Propodium widened thèse is shown in Figs43, 44. Shell length (mm) No. ofplates No. ofcusps Pitch (n) Width (^) W:P index 1.46 248 7 2.95 9.26 3.14 1.47 250 7 2.86 10.0 3.50 1.50 225 7 2.85 9.10 3.19 1.50 229 7 2.76 9.20 3.33 1.39 250 7 2.68 8.70 3.25 1.55 262 7 2.52 9.00 3.57 1.45 260 7 2.50 7.60 3.04 1.41 250 7 2.43 9.00 3.70 Table 1. Radular analysis ofCystiscus carinifern. sp. 22 A. WAKEF1ELD& T. McCLEERY NOVAPEX 6(1-2): 19-30. 10 mars 2005 Remarks. The living animais of tliis species were Type Locality. Makemo Atoll, Tuamotu observed under higii power iight microscopy and it Archipelago. was observed that ciiia were présent on tlie leading edge oftlie lower border oftlie liead/siplion compiex Distribution. Currently known only from the type (Fig 1). but cease at a point approximately halfway locality. along the tentacles. It is possible thatthe whole ofthe Habitat. Lives within interstices ofdead coral lumps 'tube' which fomis the head is lined with ciliated in shallow water (<l-3m) in and around passes in the epithelium. Histological studies will be required to reef establish the form and true functional significance of this anatomical feature, which has also been observed Description. Shell small, of two whorls (including on other as yet undescribed species of South Pacifie nucleus). transparent, smooth, glossy, triangular. Cystiscus. moderately rounded shoulder. spire low, apical callus This species was generally found in deeper water absent. Aperture fairly parallel for posteriorhalfthen than the othertwo, with most ofthe dead coral lumps widening anteriorly. Lip smooth, thickened containing spécimens coming from 3 to 7 mètres. It posteriorly. with a thin extemal varix or beading in was observed that the coral lumps in Tahanea hâve mature spécimens. Posterior edge of lip sweeps much green weed coverage, whereas this is not anteriorly then back posteriorly to insert at level of présent on the silted up coral from other atolls. The suture, forming a rostration in very mature idéal microhabitat for C. carinifer is therefore the spécimens. Distinct bulge in posterior half of last interstices of weed covered dead coral pièces, adult whorl just before lip recurves. Substantial although th^ species does seem to be able to adapt to pariétal callus extending full length of aperture, less than idéal circumstances, as evidenced by its including plications. thick enough to render shell présence on Makemo. opaque. Four strong columellar plications. occupying In contrast with most other recorded Indo-Pacitlc just less than 50% ofapertural length. First plication Cystiscus species which hâve either a banded or a strongly émergent,joining up extemally with anterior diffusely reticulated pattem ofthe interna! mantle. C. end of labial varix. Plications excavated inside cariniferhas large, bold and variable markings. aperture. Plications square in cross section, becoming Thèse markings tend to be concentrated at midbody more rounded after the excavated area as they enter and shoulder zones, which is a pattem obser\ed in within aperture. Columella weakly lirate in some some banded Cystiscus. Thus the pattem of C. spécimens. Callus wash from second columellar carinifer could be interpreted as either a banded plication passing round last adult whorl to anterior species with a very disrupted banded pattem. or an extremity. intermediate fonn between distinctly banded and Paratypes and other material examined similar in ail evenly mottled or mosaic-like pattem schemes. respects to holotype. Aduh shell size (L) range min. Further analysis of pattem schemes and their 1.46 mm, max., 1.51 mm (holotype 1.51 x 1.07 variability (both within and between species) of mm). many species of Cystiscus will be required before Animal: based on a study of several animais from meaningful conclusions can be reached. Makemo, Type 3 animal (Figs 11-15). Tentacles short, fine, situated at anteriorposition on head. Head Etymology. Cystiscus carinifer is named for the split longitudinally along superior aspect. Eyes small, latéral profile of the strongly émergent first red. set well back from tentacles within latéral bulges columellar plication (Fig 23). from the Latin carina on head. Foot half width of shell. Propodium (f): keel ofa ship. widened anteriorly. Head with a pair of weakly opaque cream Unes, medial to eyes. not extending Cystiscus mosaica n. sp. into tentacles. Internai mantle evenly very pale Figs 11-15,25-28,45-47 mauve superimposed with pale cream reticulation resulting in a mosaic-like pattem. Extemal mantle Type Material. Tuamotu Archipelago, Makemo, translucent yellowish-cream. Foot translucent with holotype(1.51 .\ 1.07 mm) MNHN (Figs 25-27). very weak opaque cream zone occupying its central Tuamotu Archipelago, Makemo, paratype (1.43 x third. mnning longitudinally down the midiine. An 1.01 mm) MNHN (Fig 28). examination of two radulae from spécimens from Tuamotu Archipelago, Makemo, paratypes, 2 Makemo was performed with the compound spécimens (1.47 x 1.05 mm, 1.45 x 1.04 mm) TMC. microscope. The results are summarised in table 2. Tuamotu Archipelago. Makemo. paratypes, 2 Thèse reveal a cystiscid type 2 radula. of230 to 276 spécimens (1.46 X 1.04 mm. 1.55 x 1.10mm)AWC. plates, each plate bearing 8 cusps (occurring due to an extra cusp adjacent to the large central cusp). The Other material examined. 1 adult & 9 juvénile width ofthe ribbon is 12.4-13.4 |am. An example of spécimens, plus 2 dead adult shells, Makemo. TMC. one ofthèse radulae is shown in figs 45-47. 23 A. WAkEFIELl)& T. McCLEF.RY Threc now species ofC'v.s7;'.v(7/.s SheU len^tth (mm) No. ofplates No. ofcusps Pitch (fi) Width (n) W:P index 1.56 230 8 3.43 13.4 3.9 1.51 276 8 2.95 12.4 4.2 Table 2. Radularanalysis ofCvsfisciis mosaica n. sp. Kemarks. Allhoiigli tlic similarities in shell caution, and not in isolation from other characters of morphology betvveen ail llircc of the species the animal and shell. dcscribed hère is protbiind. it is possible when From the point of view of animal chromatism, C. studying them in large enough numbers to perceive mosaica appears to be doser to C. nehulosa than to small différences which help in their differentiation. C. carinifer. It differs from the former in having a In the inajority of spécimens ('. mosaica has a more well defmed pattern, being overall creamy substanlial pariétal callus wash. and a miich greater insead of yellow, and in lacking the strong midiine tendency to e.xtend this calliis to the labial shoulder opacity ofthe foot and tentacies. creating a noticeable 'rostration'. particularly in older spécimens. The callus deposits ofC carinifcrand C Etymology. Named after the 'mosaic-like' pattern of iwhulosa are consistently less than those of C. the internai mantie. From French 'mosaïque', based mosaica. on Latin miisi(v)iim ('décoration with small square Comparisons betvveen C. mosaica and the other two stones'). Modem Latin mosaiciis of late middle species can also be made from observations of English origin ('pattern produced by arranging radular characters. The features found to be of togethersmall pièces ofmateriai'). importance were the cusp count and the radular widths. The cusp count of C. mosaica is higher at Cystiscus nehulosa n. sp. mainly 8 per plate compared to mainly 7 for C. Figs 16-20,29-35,48,49 carinifer and C. ncbulosa, and comes about by an extra cusp regularly appearing adjacent to the large Type Materiai. Tuamotu Archipelago, Faaite, central cusp. This e.xtra cusp in C. mosaica seems to holotype (1.40 X 0.99 mm) MNHN (Figs 29-31). relate to the greater width of the plate (approx 25% Tuamotu Archipelago, Faaite, paratype (1.58 x 1.04 mm)MNHN(Fig32). vvider than the other two species) and can therefore be considered to be a constant spécifie character. The Tuamotu Archipelago, Faaite, paratypes, 3 spécimens présence of an extra cusp vvas also observed in the (1.43 X 1.06 mm, 1.43 x 1.04 mm, 1.50 x 1.07 mm), SEM examination of C. carinifer but occurred to a AWC. much lesser extent than in C. mosaica. The Tuamotu Archipelago, Faaite, paratypes, 2 spécimens measurement of the relative widths of the radulae (1.45 X 1.05 mm, 1.45 x 1.04 mm), TMC. revealed that (in the limited number of spécimens Other materiai examined. Faaite, 35 spécimens, examined) the plate width of C. mosaica was TMC. consistently 2-3|im wider than that of C. nebulosa, and consistently 3-4|im wider than that of C. carinifer. No individual C. nehulosa radula was Type Locality. Faaite Atoll, Tuamotu Archipelago. greater than 10.45 |im in width and no individual C. Distribution. Currently known only from type mosaica radula vvas less than 12.4mm in width, locality. representing a significant 20% différence. The study ofradular characters in species differentiation in the Habitat. Lives within interstices ofdead coral lumps group Crithe/Cyslisciis is still in its infancy and as a in shallow water(<l-3 m) in and around passes in the resuit thèse observations need to be interpreted with reef. Figures 11-20 11-15. Cystiscus mosaican.sp., Makemo, Tuamotu's. 1 1. length 1.50 mm; 12-15. length 1.51 mm. Figs. 16-20 Cystiscus nehulosa n.sp., Faaite, Tuamotu's. 16. length 1.45 mm; 17. length 1.47 mm; 18-20. length 1.51 mm. 24 A. Wakefield& T. McCleery NOVAPEX 6(1-2): 19-30, 10 mars 2005 A. WaKEFIELD«S: T. McClEERY Three new species oïCystiscus Description Shell small. of two whorls (includiiig adult whorl to anteriorextremity. nucleus), transparent, smooth, glossy, triangular, Paratypes and other material examined similar in ail moderately rounded shoulder. spire low, apical calliis respects to holotype. Adult shell size range min. 1.38 absent. Aperture lairly parallel for posterior halfthcn X 0.99 mm, max. 1.58 x 1.04 mm (holotype 1.43 x widening anteriorly. Lip smooth. thickened 1.06 mm). posteriorly, with a thin extemal varix or beading in Animal: based on a study of several animais from mature spécimens. Posterior edge of lip sweeps Faaite Atoll, Type 3 animal (Figs 16-20 ). Tentacles anteriorly then back posteriorly to insert at level of short, Une, situated at anterior position on head. Head suture. Distinct bulge in posterior half of last adult split longitudinally along superioraspect. Eyes small, whorl just before lip recurvature. Marked pariétal red, set well back from tentacles within latéral bulges callus e.\tending full length of aperture, incliiding on head. Foot half width of shell. Propodium plications. Four strong columellar plications, widened anteriorly. Head with a pair of opaque occupying just less than 50% of apertural length. creamy-yellow lines, medial to eyes, each extending First plication slrongly émergent, joining up into its respective tentacle. Internai mantle creamy- extemally with anterior end oflabial varix. Plications yellow with wisps ofdarker cream forming nebulous excavated inside aperture. Plications square in cross pattem over the whole of the internai mantle. section, becoming more rounded after the excavated Extemal mantle lemon yellow. Foot translucent with area as they enter within aperture. Columella a wide opaque creamy-yellow zone occupying its weakly lirate in some spécimens. Thin callus wash central third, running longitudinally down the from second columellarplication passinground last midline. Shell length (mm) No. ofplates No. ofcusps Pitch (^) Width (|u) W:P index 1.54 223 7 3.10 10.45 3.37 1.46 245 7 2.96 10.0 3.40 1.46 223 7 2.74 10.1 3.70 Table 3. Radularanalysis oïCystiscus nebulosa n. sp. An examination of three radulae from spécimens Tahanea (see Fig 4). In addition C. nebulosa and C. from Faaite was performed under the compound carinifer, both bear strong opacities in the midline of microscope. The results are summarised in table 3. the foot, and head and tentacle régions. We hâve Thèse reveal a cystiscid type 2 radula, of223-245 v- noted however that within populations of both shaped overlapping plates, each plate approximately species that there is some variability in the 10 |im wide and bearing 7 cusps. Examples oftwo of development of thèse opacities, in that the head thèse radulae are shown in figs48 and49. markings in occasional spécimens exhibit unilatéral incomplète development (Figs 2, 17). The foot Remarks. When attempting to make comparisons markings are also variable in their présentation (Figs and establish links between différent species of 3, 4, 6, 10, 17, 18). Based upon thèse features, we Cystisciis whose shells are extremely similar, a close conclude that there is a close relationship between C. examination ofthe chromatism ofthe animais is the carinifer and C. nebulosa. The différent structure of most important way of determining their the reticulated pattem on the mantle of C. mosaica, relationships. We hâve observed that the 'billowing and the absence of body opacities leads us to the cloud-like' pattem of the intemal mantle of C. conclusion that C. mosaica is not as closely related to nebulosa is also présent in the white zones on the the othertwo as theyareto each other. mantle of many spécimens of C. carinifer from Figures 21-35 Figs. 21-24 C. carinifern.sp., Tahanea, Tuamotu's, 7 mètres in dead coral. 21-23. Holotype (1.56 X 1.05 mm) MNHN; 24. Paratype 1 (1.43 x 1.07 mm) MNHN. Figs. 25-28 C. mosaica n.sp., Makemo, Tuamotu's, 2 mètres in dead coral. 25-27. Holotype (1.51 x 1.05 mm) MNHN; 28. Paratype 1 (1.43 x 1.01 mm) MNHN. Figs. 29-35 C. nebulosan.sp., Faaite, Tuamotu's, 3 mètres in dead coral. 29-31. Holotype (1.40 x 0.99 mm) MNHN; 32. Paratype 1 (1.58 xl.04 mm) MNHN; 33-34. Détail ofplications; 35. View from below illustrating labial bulge in a mature adult spécimen. 26 A. Wakefield& T. McCleery NOVAPEX 6 (1-2): 19-30, 10 mars 2005 A. WAKt:FIELD& T. McCLEERY Thrcc now species o\'Cyslisciis Etyniulogy. Named attcr ihe 'cloiid-like' patterii ot" The method of collection employed by the authors thc internai niantle. Latin nchulosus from nehiila precludcd most behavioural observations of ('mist'). Origni late niiddlc Hnglisli (in the scnsc iiidividual animais in their natural habitat. However, 'cloudy'). the second author repeatedly observed that a return visit to a previously cystiscid rich site the day DISCUSSION following initial sampling often yielded a disappointingly lovv numbcr ofspécimens, or none at The Cystiscidae of shallow reef formations of New ail. A probable e.xplanation for this is that colonies ol" Caledonia were recently reviewed by Boyer(2003) in Cyslisciis are often small or very compact and they a paper covering the gênera GihhcniUi. Crirhc. were thercfore casily misscd on the second occasion. rit'siocystisciis and QvsV/.vcv/.v. Previously named For e.xamplc during the lirsl expédition to laaite in species were reviewed and many new species were the Tuamotu's, 8 adult spécimens of C. nchulosa described, incliiding thirteen new species of were ail collected during one snorkelling session Cyslisciis. Two of thèse. C. gotibinl (Bavay, 1922) only. Four further efforts were made in the 100 and C. parJiis (Boyer. 2003). could be considered mètres (approx.) of reef edge there présent, analogous wilh C. mosuiai n.sp. and C. nchulosa specifically in the hope of tlnding more of this n.sp. respeclively, in that they share similar pattern particular species. but none were found until a second design of their internai mantles. An objective search was performed there two years later. From this comparison ofthe animal is difficult to achieve when it can be deduced that in silty. perhaps less than idéal comparing drawings with pholographs. but the habitats they form compact colonies of animais internai mantle of C. mosaica does appear to hâve a restricted to a single coral lump rather than being similar mosaic-like reticulated pattem to that of the evenly and thinly distributed across the reef. and that pa\ing pattern" [sic] of C. goiihini as shown in the neighbouring colonies are indeed présent but are few drawings and description ofthe live animal in Boyer and far between with only occasional coral lumps (2003). However, the base colour of the internai being colonised. mantle is not the same in thèse two species, being a At other localities, presumably where conditions are pale cream in C. mosaica and greyish blue in C. more favourable, large populations can be goiihini. An additional différence is that the average encountered. For example, spécimens of C. carinifer shell length of C goiihini (1.9 to 2.3 mm) is from Tahanea were found with regularity on repeated considerabiy greater than that ofC. mosaica (1.46 to dives involving two reefs and covering a large area. 1.51 mm). v\ith no overlap. The relationship between The reef Systems and water clarity in Tahanea are C. nchulosa and C. panhis seems doser. The internai particularly pristine, and it seems that such mantle pattern. présence ofwhite opacity in the foot, conditions favour the establishment of large shell size and morphology are shared characters. widespread populations instead of smaller and more Again. the colouration of the mottled areas in the isolated ones. internai mantle differ. with C. pardiis being greyish The small population of C. carinifer encountered on blue on a yellowish background. compared to yellow Makemo is possibly derived from a dispersai from on a paleryellow background in C. nchulosa. the main population in Tahanea. The Makemo habitat Unlike the two New Caledonian species. C. mosaica is not as idéal as that found in Tahanea which and C. nchulosa wère not found in micro-sympatry. suggests that in this species at least there is some During the course of our fieldwork and subséquent capacity for dispersai and an ability for a sustainable study ofthe material obtained, it has been possible to population to adapt to a slightly différent habitat. If make some observations on shallow water such dispersai events and adaptations were to be représentatives of the genus Cvstiscus in the South commonplace in this group Crithe/Cystiscus, it Pacific. would provide an explanation for its great diversity. Figures 36-49 Figs36-44 Radula ofC. carinifer, Tahanea. 36-38. Scanning électron microscope views ofradula; 39. Diagrammatic représentation oflatéral view ofa single plate; 40-42. Diagrammatic représentation ofplate variability due to unilatéral and bilatéral division of latéral cusp; 43-44. Compound microscope view ofradula (from shell 1.39 x 1.01 mm). Mag. x2750. Figs 45-47 Radula ofC. mosaica, Makemo. (from shell 1.56 x 1.01 mm). Mag. xl400. 45. Focused on cusps; 46. Focused mid-way through plates; 47. Focused on back ofplates. Figs 48-49 Radula ofC. nchulosa, Faaite. 48. From shell 1.54 x 1.04. Mag. xl250; 49. From shell 1.46 x 1.05. Mag. x2700. 28