ZOOSYSTEMATICA ROSSICA, 19(2): 196–204 30 DECEMBER 2010 Retusa pellucida (Brown, 1827) (Gastropoda: Opisthobranchia: Cephalaspidea) from the Barents Sea – a new species for the fauna of Russian Arctic seas Retusa pellucida (Brown, 1827) (Gastropoda: Opisthobranchia: Cephalaspidea) из Баренцева моря – новый вид для фауны арктических морей России E.M. CHABAN* & I.O. NEKHAEV E.M. ЧАБАН* & И.O. НЕХАЕВ E.M. Chaban, Zoological Institute, Russian Academy of Sciences, 1 Universitetskaya Emb., St. Petersburg, 199034, Russia. E-mail: [email protected]. *Corresponding author. I.O. Nekhaev, Murmansk Marine Biological Institute of Kola Scientific Centre, Russian Academy of Sciences, 17 Vladimirskaya St., Murmansk, 183010, Russia. E-mail: [email protected] Retusa pellucida (Brown, 1827) recorded the first time for the recent fauna of the Russian Arctic. New data on morphology of its soft part are given. Shell sculpture of Retusa pellucida is discussed in comparison with R. truncatula (Bruguière, 1792) and related forms. Retusa pellucida (Brown, 1827) впервые отмечена для современной фауны арктических морей России. Приведены новые данные по морфологии головного копулятивного аппа- рата и пластинок жевательного желудка этого вида. Обсуждается скульптура раковины Retusa pellucida в сравнении с R. truncatula (Bruguière, 1792) и близкими к ней формами. Key words: Barents Sea, morphology, shell sculpture, male copulatory system, Gastropoda, Cephalaspidea, Retusidae, Retusa pellucida Ключевые слова: Баренцево море, морфология, скульптура раковины, головной копуля- тивный аппарат, Gastropoda, Cephalaspidea, Retusidae, Retusa pellucida INTRODUCTION complete in Lemche (1948). However even Lemche (1948: 83) distinguished pellucida Retusids with a semi sunken truncated as a “shell variety”. At present some authors spire were collected from off the Murmansk still consider Retusa pellucida (Brown, coast of the Barents Sea. We believe that 1827) to be a synonym of Retusa truncatula this is the same species as the one described (Jensen & Knudsen, 1995; Høisaeter, 1986, by Sars (1878: 285, Tab. 17, Fig. 18) under 2009) while others – as a distinct form or the name Utriculus truncatulus var. pellucida species but attributed to Sars (Nordsieck, attributed to Brown. 1972; Cervera et al., 1988; Bouchet et al., Volvaria pellucida Brown, 1827 which 2001; Gofas, 2009; Garsía & Bertsch, 2009). had been described as a distinct species Morphological features of the material col- was later considered to be a variety of Re- lected off the Murmansk Coast of the Bar- tusa truncatula (Bruguière, 1792) (Jeffreys, ents Sea correspond to those given in the 1867; G.O.Sars, 1878; Pilsbry, 1893; Odh- descriptions and illustrations of Volvaria ner, 1907) and was included into the list of pellucida in Brown (1827, 1844) and Utricu- synonyms of R. truncatula, which is the most lus truncatulus var. pellucida in Sars (1878). © 2010 Zoological Institute, Russian Academy of Scienсes E.M. CHABAN & I.O. NEKHAEV. RETUSA PELLUCIDA FROM RUSSIAN ARCTIC 197 We consider R. pellucida to be a valid species SYSTEMATIC PART because of significant differences of its shell Order CEPHALASPIDEA Fischer, 1883 sculpture from the sculpture of R. trunca- tula. The descriptions given by Brown and Family RETUSIDAE Thiele, 1926 Sars are very short, so we provide below a Retusa Brown, 1827 detailed description of the shell, copulatory Retusa pellucida (Brown, 1827) apparatus and gizzard plates of R. pellucida. (Figs 1, 2–5, 11–14) MATERIAL AND METHODS Volvaria pellucida Brown, 1827: pl. 38, figs 45– 46; 1844: 4, pl. XIX, figs 45–46. The specimens of R. pellucida (Brown, Utriculus truncatulus var. pellucida – Jeffreys, 1827) was collected during expeditions of 1867: 422; G.O. Sars, 1878: 285, tab. 17, the Murmansk Marine Biological Institute fig. 18. of the Kola Scientific Centre of the Rus- Retusa truncatula var. pellucida – Pilsbry, 1893: sian Academy of Sciences (MMBI KSC 206. RAS) from the Murmansk coast of the Bar- Rerusa truncatula (shell variety pellucida ents Sea (Fig. 1): 1. Ura-Guba, 29–31 Aug. Brown)– Lemche, 1948: 55–56, 83, fig. 57. 2007, 11 specimens from 6 lots, collected Retusa truncatula (non Bruguière, 1792) – with Petersen grab (0.04 m2); 2. Teriberka Thompson, 1976: fig. 55h. Bay, 22 Oct. 2010, 1 specimen from lot of Retusa (Coleophysis) truncatula form pellucida G.O. Sars, 1878 – Nordsieck, 1972: 34, taf. 0.625m2, diving collection; 3. Yarnishnaya V, fig. 5. Bay, 3 June 2009, 1 specimen, van-Vin grab Retusa pellucida (G.O.Sars, 1878) – Cervera et 0.1m2, 80.5m, R/V “Dal’niye Zelentsy”. The al., 1988: 13; Bouchet et al, 2001: 199; Garsía specimens were firstly fixed in 4% formal- & Bertsch, 2009: S3; Gofas, 2009. dehyde and then transferred to 70% alcohol for storage. The specimens have been depos- Type material. Whereabouts unknown. ited at ZIN and MMBI KSC. Type locality. “On the beach at Dunbar”, Comparative material. Sixteen dry speci- [the southeast coast of Scotland, the North mens with well preserved shell sculpture Sea] (Brown, 1827). from off Tropani, Mediterranean Sea, col- Material examined. Barents Sea, Kola lected and identified by Monterosato as Co- Peninsula, Ura–Guba: 31 Aug. 2007, 5 m leophysis semisulcata var. pellucida Brown, depth, No. 1 – 1 specimen; 31 Aug. 2007, 1827, deposited at the Zoological Institute, 25 m, No. 2 – 2 specimens; 29 Aug. 2007, Russian Academy of Sciences, St. Peters- burg (ZIN), no. 1/23286. Four dry speci- mens of R. truncatula from Jersey Island, off the northwest coast of France, collected and identified by Milaschewitsch, deposit- ed at ZIN, no. 2/23290. Two dry specimens of Retusa truncatula from Crimea, the Black Sea, collected by S.A. Zernov on 15 Au- gust – 15 September 1909, station 10, R/V “Meotida”, identified by Milaschewitsch, deposited at ZIN, uncatalogued. A scanning electron microscope HI- TACHI S-570 (SEM) and a light micro- scope Leica DMLS-2 were used. Whole pe- nises were mounted in balsam with carmine Fig. 1. New recorded localities of Retusa pellu- staining using a standard procedure for ex- cida in the Barents Sea. 1 – Ura–Guba, 2 – Teri- amining with a light microscope. berka Bay, 3 – Yarnishnaya Bay. © 2010 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 19(2): 196–204 198 E.M. CHABAN & I.O. NEKHAEV. RETUSA PELLUCIDA FROM RUSSIAN ARCTIC Figs 2–10. Retusa pellucida, Ura-Guba, nothern coast of the Kola Peninsula, Barents Sea: 2, shell, ventral view; 3, details of sculpture; 4, shell, apical view; 5, posterior end of the shell. Retusa semisul- cata, specimen collected and identified by Monterosato as Coleophysis semisulcata var. pellucida: 6, shell, ventral view; 7, shell, apical view; 8, details of sculpture; 9, original label by Monterosato; 10, posterior end of the shell. Scale bar: 1 mm (2, 6), 0.5 mm (3–5, 7, 8, 10). © 2010 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 19(2): 196–204 E.M. CHABAN & I.O. NEKHAEV. RETUSA PELLUCIDA FROM RUSSIAN ARCTIC 199 Figs 11–14. Retusa pellucida, Ura-Guba, nothern coast of the Kola Peninsula, Barents Sea. 11, un- pared gizzard plate, inner view; 12, pared gizzard plate, lateral view; 13, male copulatory system, dorsal view, specimen 2.6 mm in length; 14, male copulatory system, ventral view, specimen 2.0 mm in length; in – incurrent sperm groove, m.o – opening of the male copulatory system, p – penis, pr – prostate, ps – penis sheath. Scale bar: 0.10 mm (13, 14), 0.25 mm (12), 0.40 mm (11). 5 m, No. 3 – 1 specimen; 29 Aug. 2007, elongated, posteriorly truncate with slight- No. 4 – 1 shell; 28 Aug. 2007, No. 5 – 6 ly conical sides (Fig. 2). Spire concave with specimens. Yarnishnaya Bay: 3 June 2009, 2.0–2.5 whorls (Figs 4–5). Protoconch cir- 80.5 m depth – 1 specimen. cular, not protruding from the first whorl, Description. Shell morphology. Length about 0.18mm in diameter. Umbilicus very from 1.8 to 2.8 mm; width up to 1.4 mm in narrow. Columella simple, with no folds. the largest specimen examined. Shell fragile, Aperture lip forming a rounded wing pos- © 2010 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 19(2): 196–204 200 E.M. CHABAN & I.O. NEKHAEV. RETUSA PELLUCIDA FROM RUSSIAN ARCTIC Figs 15–21. Retusa truncatula. 15, 16, 18, from Jersey Island, near northwest coast of France, col- lected and identified by Milaschewich: 15, specimen with well-preserved sculpture, shell, ventral view; 16, worn shell, ventral view 18, the same, apical view. 17, specimen from Crimea, Black Sea, identified by Milaschewich. 19, shell, ventral view, Black Sea, Romania (after Grossu, 1956, Fig. 99, as R.truncatula var. opima, 4.5–7 mm). 20, shell, ventral view, Denmark, (after Lemche, 1948, Fig. 55, 3 mm). Fig. 21, Retusa pellucida, shell, ventral view, Denmark (after Lemche, 1948, Fig. 57, 3 mm, as a shell variety pellucida of Retusa truncatula). Scale bar: 1.0 mm (15–18). © 2010 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 19(2): 196–204 E.M. CHABAN & I.O. NEKHAEV. RETUSA PELLUCIDA FROM RUSSIAN ARCTIC 201 teriorly rising above the body whorl. An- DISCUSSION terior end of the shell rounded. Columellar Brown described his species Volvaria pel- margin not S-shaped, it is almost straight. lucida from the North Sea as “…smooth, thin, Sculpture with several conspicuous growth pellucid” in contrast to Volvaria truncata lines with traces of secondary sculpture vis- [?=Bulla truncata J. Adams, 1800; = Bulla ible as 2–3 shallow grooves between neigh- truncata sensu Montagu (1803: 223, tab. 7, boring growth lines (Fig. 3). Spiral sculp- fig. 5)] (“…upper part longitudinally stri- ture absent. Colour uniformly whitish. Pe- ated, for about a third its length”) (Brown, riostracum pellucid thin when present. 1844:4). Sars (1878: 285) identified his Anatomy. Digestive system containing three oval gizzard plates. Plates convex specimens from Lofoten as Utriculus trunca- with dark tubercles, mostly small, with tulus var.pellucida by reference to Volvaria few larger and higher tubercles posteriorly pellucida Brown; he described the speci- (Figs 13–14). Unpared plate oval (Fig. 13), mens as “superficie laevissima, plicis nullis” pared plates elongated and more convex in contrast to Utriculus truncatulus forma (Fig. 14). Male copulatory organ on right typica (“superficies in parte dimidia superiore side of oesophagus in specimen 2.6 mm in dense longitudinaliter plicata, plicis angustis, length; atrium long, with seminal groove, acutis”). The descriptions and images of pel- prostate short and wide, lies parallel to lucida by the two authors do not contradict body axis, filled with shining cells (Fig. each other. The indication by some authors 11). Penis composed of muscle folds in pe- of G.O. Sars as the author of pellucida appar- nis sheath. Penis not developed in specimen ently came from Nordsieck: “Form: pelluci- 2.0 mm length, its copulatory organ curved, da G.O. Sars, 1878. Norwegen” (Nordsieck, prostate perpendicular to internal seminal 1972: 34). groove and to body axis (Fig. 12). The description of R. truncatula in Bru- Ecology. Collected from 5–80.5 m in the guiere (1792, in Bulla) does not contain in- Barents Sea on sand and mud with a few dry formation about the sculpture of the shell shells and sometimes stones. (“Bulla, testa cylindrica laevi candida, ap- Distribution. Described from the south- ertura sublineari, spira truncata”). The de- east coast of Scotland, the North Sea, col- scription of Retusa truncata (Adams, 1800: lected from Lofoten, the Norwegian coast, tab. 1, figs 1, 2, in Bulla), a junior objective the Norwegian Sea (Sars, 1878) and from synonym of R. truncatula (International the Murmansk coast of the Barents Sea Comission Opinion No. 549) is even shorter (present study), noted for Atlantic and (“B. [Bulla] testa subovali apice truncata”), Mediterranean coasts of Spain (Cervera et and its pictures do not show any sings of al., 1988). longitudinal sculpture. Nevertheless R. Note. Molluscs of the truncatula group truncatula has been described as usually was recorded for the Post-Pliocene fauna having numerous longitudinal striae or ribs of the Murmansk coast of the Barents Sea on the upper half of the shell (Jeffreys, 1867; by Knipowitsch (1900). He identified Pilsbry, 1893; Milaschewich, 1916; Pruvot- specimens collected by V. Faussek in 1887 Fol, 1954). Truncated shells with well defi- from Port Vladimir, Ura-Guba, 9 m and nite longitudinal folds but different from by B. Popov on 28 July 1899 from depths R. truncatula by the shell proportion were of 17–14 and 75 m as Utriculus truncatulus. described as species or varieties. For exam- It seems that findings of R. truncatula along ple, Bulla semisulcata Philippi, 1836 having the Norwegian coast including the Varang- “…superne longitudinaliter sulcata, … vertice erfjord area (Høisaeter et al., 1997; Høi- truncato…” (Philippi, 1836: 123, t. VII, fig. saeter, 2009) may also refer, at least partly, 19) was considered as a distinct valid spe- to R. pellucida. cies (Monterosato, 1884: 142) “…more elon- © 2010 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 19(2): 196–204 202 E.M. CHABAN & I.O. NEKHAEV. RETUSA PELLUCIDA FROM RUSSIAN ARCTIC gated than Retusa truncatula, with straighter close forms on the other hand becomes much longitudinal folds, and a wide transparent more evident. We compared the specimens zone” (Pilsbry, 1893: 206) or a synonym of R. pellucida from the Barents Sea with the of R. truncatula (Vayssière, 1885; Lemche, specimens of R. semisulcata, identified by 1948); it is not included in the list of Euro- Monterosato as Coleophysis semisulcata var. pean moluscs (Bouchet et al., 2001). Retusa pellucida (Figs 6–10). Coleophysis Fischer, truncatula var. opima Milaschewich, 1909 1883 is synonym of Retusa, or sometimes re- “... differs from the typical form by a wider ferred to as its subgenus. Retusa semisulcata cylindrical shape” (Milaschewich, 1916; may be a distinct species or a synonym of R. Grossu, 1956: fig. 19). Similarly, R. pellu- truncatula; with regards to the shell sculp- cida was earlier considered to be a variety of ture morphology they are very similar in the R. truncatula : “Smaller, shorter, thinner and upper 2/3 of the shell. Among specimens ex- more transparent, slightly less strongly ribbed amined by us the specimens of R. semisulcata or sometimes quite smooth…” (Jeffreys, 1867: possess better integrity. Longitudinal growth 422; Pilsbry, 1893: 206) or, later, as a valid lines of the specimens from the Barents Sea species (Cervera et al., 1988; Bouchet et run through the entire length of the shell; al., 2001). However, Thompson (1976) de- two or three secondary grooves, interspaced scribed R. truncatula as having “ sculpture between two next growth lines, are slightly consisting of fine longitudinal striae” refer- visible at the SEM images (Fig. 3). “Retusa ring to Lemche (1948: Figs 55, 57) (shown semisulcata var. pellucida” from Tropani has here in Figs 20, 21) and to Meyer and Mö- longitudinal folds (ribs) on the upper part of bius (1865). the shell, pellucid transverse band (not seen This makes identification of R. trunca- on scanned images) and S-shaped line of tula ambigous and taxonomic status of R. the inner lip of the mouth. At the SEM im- pellucida debatable. ages we can see the secondary longitudinal The examined specimens from Ura-Guba sculpture looking like five-six closely spaced have no pronounced differences in structure grooves located between two adjacent ribs. of the gizzard plates (Figs 13–14) and in pe- These grooves run along the entire length of nial morphology (Fig. 11–12) in comparison the shell. The pattern of the sculpture with with R. truncatula as described in Mikkelsen its primary and secondary elements are re- (1995: 206, Fig. 2F). However, their sculp- vealed also for the R. truncatula – group by ture is considerably different. We compared Berger (1953). The two species also differ the shell sculpture of our specimens from by the configuration of the inner lip. The the Barents Sea with R. truncatula from the inner lip in the specimens from the Barents Black Sea and the north-western coast of Sea is almost straight as it is illustrated for France identified by Milaschewich. At low pellucida by Sars (1878: Tab. 17, Fig. 18) in magnification, the shell of R. pellucida looks contrast to the Tropani specimens with a S- smooth with irregular growth lines. Retusa shaped inner lip. truncatula from the Balck Sea and from off In the revision of the types of the opist- the Jersey Island have prominent ribs grad- hobranch gastropods described by Monte- ually smoothed out to the base of the shell rosato, Oliverio & Tringali (2001) have as described by Milaschewich (1916) and found the type material of Coleophysis effu- Pruvot-Fol (1954). Even if the shell is worn sa Monterosato, 1890. It is a weakly sculp- (Fig. 16), its apex is still bearing the well tured form (Oliverio & Tringali, 2001: Figs visible ribs (Fig. 18). The ribs are well pro- 31, 32) which considered by the two authors nounced even in relatively small specimens to be close to “pellucida” Brown, 1827. Co- (Fig. 17). When the shell sculpture is exam- leophysis effusa is quite similar to our speci- ined using a SEM, the difference between R. mens, but it has a different S-shaped line of pellucida on one hand and R. truncatula and the inner lip. Oliverio and Tringali noted © 2010 Zoological Institute, Russian Academy of Scienсes, Zoosystematica Rossica 19(2): 196–204 E.M. CHABAN & I.O. NEKHAEV. RETUSA PELLUCIDA FROM RUSSIAN ARCTIC 203 that it was hard to say whether effusa could berg, G. World marine mollusca database. represent merely a form, or a distinct spe- Accessed through the World Register of Ma- cies within the probable complex of R. trun- rine Species at http://marinespecies.org/ aphia.php?p=taxdetails&id=141135 [cited catula, all this group being poorly known. 8 June 2010]. Grossu, A.V. 1956. Gastropoda Prosobranchia si ACKNOWLEDGEMENTS Opisthobranchia. Fauna Republicii Populare Romine. Mollusca. Vol. 3. Fascicula 2. Edit- We are grateful to T.K. 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