taxonID	type	description	language	source
24370F05FF9D074FFCFC8E07FB8C21F8.taxon	type_taxon	Type species. Eolis salmonacea Couthouy, 1838, by original designation. Diagnosis. Body wide; head rounded; notal edge present, well-developed, continuous; rhinophores smooth to rugose; cerata in rows, attached directly to notum, unstalked; anus pleuroproctic on posterior right side of body; oral glands absent; jaws triangular with denticulated masticatory process; triserial radula; rachidian teeth with strong elevated blunt cusp and large denticles on each side; lateral teeth narrow, triangular, with minute denticles on inner edge or denticles absent; seminal receptacles absent; vas deferens long; penial gland absent; unarmed penis. Species included: Ziminella abyssa Korshunova et al., 2017, Ziminella japonica (Volodchenko, 1941), Ziminella salmonacea (Couthouy, 1838), Ziminella vrijenhoeki Valdés et al., 2018.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF9D0741FCFA88ECFD67253E.taxon	description	(Figs 3 A – C, 4 – 6)	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF9D0741FCFA88ECFD67253E.taxon	materials_examined	Type material. For Z. salmonacea the type material is not known [Martynov, 2006]. The type material for Z. circapolaris syn. nov. (Holotype ZMMU Op- 598) is hosted at Zoological Museum of Lomonosov Moscow State University. Material studied. Barents Sea, 70 ° 58 ’ N 37 ° 07 ’ E, 161 – 170 m depth, coll. Knipowitsch N. 19.07.1899, ZIN 24520 (4 spm). Barents Sea, Teriberskaya Guba, 110 – 146 m depth, coll. Knipowitsch N., 21.07.1894, ZIN 24526 (1 spm). Barents Sea, Novaya Zemlya, Gorbovy Isl., 11 m depth, coll. Ushakov P. V., Gorbunov, 04.09.1927, ZIN 24527 (2 spm). Barents Sea, 69 ° 34 ’ 30.0 ” N 32 ° 00 ’ 31.0 ” E, 202 m depth, coll. Knipowitsch N., 13.07.1899, ZIN 24528 (3 spm). Barents Sea, 74 ° 08 ’ N 20 ° 00 ’ E, 155 m depth, coll. Knipowitsch N., 16.04.1900, ZIN 24529 (1 spm). Barents Sea, 74 ° 08 ’ N 20 ° 00 ’ E, 155 m depth, coll. Knipowitsch N., 16.04.1900, ZIN 24530 (1 spm). Barents Sea, Novaya Zemlya, 72 ° 29 N 51 ° 21 ’ E, 73 – 74 m depth, coll. Knipowitsch N., 19.07.1901, ZIN 24531 (2 spm). Barents Sea, 70 ° 58 ’ N 37 ° 07 ’ E, 161 – 170 m depth, coll. Knipowitsch N., 19.07.1899, ZIN 24532 (1 spm). Barents Sea, Ura Bay, 69 ° 23 ’ 00.0 ” N 32 ° 55 ’ 00.0 ” E, 271 m depth, coll. Knipowitsch N., 26.05.1901, ZIN 24533 (1 spm). Kara Sea, 80 ° 1.5 ’ N 73 ° 20 ’ E, 41 m depth, coll. Vagin, 18.08.1934, ZIN 24535 (2 spm). Barents Sea, Kola Bay, 220 m depth, coll. Knipowitsch N., 11.06.1898, ZIN 24537 (1 spm). Barents Sea, Ura Bay, 235 m depth, coll. Knipowitsch N., 17.06.1902, ZIN 24540 (1 spm). Barents Sea, 69 ° 18 ’ 14.8 ” N 33 ° 41 ’ 57.4 ” E, 72 m depth, coll. Knipowitsch N., 28.06.1898, ZIN 24545 (1 spm). Franz Josef Land, Heiss Is., 5 – 7 m in depth, coll. Pushkin, 01.02.1982, ZIN 63736 (1 spm). NW Atlantic, off Newfoundland, 48 ° 55.5 ’ N 50 ° 31.4 ’ W, 230 – 237 m depth, coll. Nesis K. N., 14.07.1959, ZIN 63739 (3 spm). Western Greenland, 69 ° 55 ’ 1 ” N 51 ° 16.2 ” W, 7 m depth, coll. Sirenko B. I., 21.07.1993, ZIN 63740 (12 spm). Barents Sea, Novaya Zemlya, Gorbovy Isl., 11 m depth, coll. Ushakov P. V., 04.09.1927, ZIN 63741 (3 spm). Franz Josef Land, Apollonov Is., 3 – 4 m depth, coll. Averintsev, 30.09.1992, ZIN 63746 (1 spm). Type locality. Charles River, Massachusetts, USA.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF9D0741FCFA88ECFD67253E.taxon	description	Description. External morphology (based on studied specimens): Body length up to 40 mm. Body wide. Foot wide, anterior corners short, rounded. Notal edge well-developed, continuous, forming short elevation above lateral body sides. Oral tentacles elongated, conical. Rhinophores smooth to rugose, longer and thinner than oral tentacles. Cerata in distinct rows, attached directly to well-defined notal edge. Cerata fusiform to cylindrical, lateral cerata much smaller than dorsal. Digestive gland diverticula filling more than half of ceratal volume. Anal opening on right side below notal edge, at beginning of posterior half of body. Reproductive opening on right side, on anterior part of body, surrounded by slightly folded region. Coloration [after Kuzirian, 1977; 1979; Roginskaya, 1987]: Background body color milky-white. Oral tentacles and rhinophores beige to light orange with distal white stripe. Cerata orange-tan to deep red-brown, distal tip with white ring. Internal morphology (based on studied specimens): Jaws oval-triangular with well-developed masticatory border bearing several rows of low blunt denticles or elevations. Radular formula: 19 – 32 × 1.1.1. Rachidian teeth massive, triangular. Central cusp strong, conical and elongated, non-compressed by adjacent denticles. From 4 to 11 small sharp and slightly curved denticles on each side of cusp, commonly from 6 to 9, denticles of about same size. Lateral teeth narrow, slightly curved blades with variable denticulation. From 0 to 29 denticles on inner side, locating at base, on first half or on entire length of tooth. Reproductive system diaulic. Ampulla long, narrow and convoluted. Vas deferens extremely long with slightly expanded prostatic part. Penis conical to slightly folded. Seminal receptacle absent.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF9D0741FCFA88ECFD67253E.taxon	distribution	Distribution. This species possesses a wide geographic and bathymetric distribution in the North Atlantic and adjacent Arctic waters. Based on Kuzirian [1979], Roginskaya [1987], Korshunova et al. [2017], and the material from BOLD and ZIN collections, the known range of Z. salmonacea includes Massachusetts, Maine, Bay of Fundy, New Brunswick, Newfoundland, Western Greenland, waters off Canadian Arctic Archipelago, Iceland, Northern Norway, Svalbard, Franz Josef Land and the Barents, the White and the Kara seas, on depths from 3 to 271 m.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF9D0741FCFA88ECFD67253E.taxon	discussion	Remarks. Our morphological and molecular data suggest that Z. salmonacea and Z. circapolaris should be considered a single species. Ziminella circapolaris was described based on specimens from the Franz Josef Land, as it “ forms a separate sister clade to Z. salmonacea ” [Korshunova et al., 2017: 22]. According to Korshunova et al. [2017] these two species differ in the denticulation of the lateral teeth, as in Z. circapolaris the “ denticulation runs up to very end of the lateral teeth, and the teeth are always denticulated ”, while in Z. salmonacea the denticles are restricted to the first half of the laterals [Korshunova et al., 2017: 23]. Finally, it was noted that the separate status of Z. circapolaris is “ concordant with a considerable level of endemism of the nudibranch fauna of Franz Josef Land ” [Korshunova et al., 2017: 23]. Our data suggests that none of above-mentioned arguments could be used to delineate these species. First of all, the specimen from BOLD database (HLC- 30139) collected from the Canadian Arctic, has the same haplotype as Z. circapolaris (Fig. 2 A), rejecting the idea of endemic status for the latter. Although Z. salmonacea and Z. circapolaris (with an inclusion of HLC- 30139) formed two distinct clades on the BI tree, the ML analysis did not separate them (Fig. 2 B, Fig. S 1). The validity of Ziminella circapolaris was not supported by the species delimitation analysis (even if we consider HLC- 30139 represents the same species), and this species also does not show any difference from Z. salmonacea in sequenced nuclear markers (H 3). Finally, we have studied a large collection of Z. salmonacea deposited in ZIN, including the slides with isolated radulae (Tables S 1, S 4). Accordingly, the lateral teeth denticulation varies greatly in specimens collected across distant localities, in a single locality (including Franz Josef Land) or even at the same site (Fig. 4, 5). In fact, several specimens from Franz Josef Land possess weakly denticulated (Table S 4, Figs 5 B, C) or even almost smooth (Table S 4, Figs 5 D, G, H) lateral teeth. At the same time, dense denticulation was observed in a specimen from Severnaya Zemlya Is. (Table S 4, Figs 5 J – L). Specimens from the North-West Atlantic and western Arctic sectors also showed variability in denticulation (Fig. 4, Table S 4) and the same has already been reported for the specimens of Z. salmonacea collected close to the type locality [Morse, 1971]. Moreover, in the SEM image of Z. salmonacea radula provided by Korshunova et al. [2017], the denticulation reaches the top of the lateral teeth [Korshunova et al., 2017: fig. 15 G]. Thus, we consider this variability to be intraspecific rather than interspecific. It was previously suggested that this variation could be ontogenetic, as Morse [1971] indicated that lateral teeth commonly have fewer denticles on the anterior part of the radular ribbon. In our material, this tendency is not traceable overall (Table S 4), although in some radulae the anterior radular portion may possess denser denticulation of the lateral teeth. Ziminella salmonacea shows minor but consistent morphological differences with other species of the genus. From Z. abyssa it differs by consistently fewer number of denticles on the rachidian teeth (from 10 to 19 in Z. abyssa), also in the latter species the lateral teeth never have well-developed denticles (Fig. 7). In Ziminella japonica and Z. vrijenhoeki the lateral teeth have much wider base, with denticulation always occurring in the first half of its internal edge (Fig. 9) [Valdés et al., 2018]. Also, Z. japonica has different coloration with distinct orange to reddish dorsal surface and rhinophores (Figs 3 F, G).	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF930744FF7E8C2AFE7F27CB.taxon	description	(Figs 3 D, E, 6, 7)	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF930744FF7E8C2AFE7F27CB.taxon	materials_examined	Type material. Holotype ZSM Mol- 20100647 deposited at Bavarian State Collection of Zoology, Munich. 153 paratypes (ZMMU Op- 248 – Op- 250, Op- 252, Op- 253, Op- 255 – Op- 259, Op- 264) deposited at Zoological Museum of Lomonosov Moscow State University. Material studied. Sea of Japan, R / V “ Vityaz ”, st. 6658, 40 ° 37 ’ 8 ” N 134 ° 07 ’ 0 ” E, 3580 m depth, 16.06.1972, ZIN 63735 (6 spm). All specimens were dissected. Type locality. Sea of Japan, 43 ° 01 ’ 42.9 ” N 135 ° 04 ’ 32.7 ” E, 2676 m depth.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF930744FF7E8C2AFE7F27CB.taxon	description	Description. External morphology (based on studied specimens): Body length up to 25 mm. Body wide. Foot wide, anterior corners short, rounded. Notal edge well-developed, continuous, forming short elevation above lateral body sides. Oral tentacles elongated, conical. Rhinophores slightly rugose, same length as oral tentacles, thinner than oral tentacles. Cerata in distinct rows, attached directly to well-defined notal edge. Anal opening on right side below notal edge, at beginning of posterior half of body. Reproductive opening on right side, on anterior part of body. Coloration [after Korshunova et al., 2017]: Background body color translucent milky-white. Rhinophores light orange at base and pale on rest of length. Cerata dark violet. Internal morphology (based on studied specimens): Jaws massive, oval-triangular with well-developed masticatory border bearing several rows of low blunt denticles or elevations. Radular formula: 22 – 31 × 1.1.1. Rachidian teeth large, triangular. Central cusp conical, wide and rather short, non-compressed by adjacent denticles. From 10 to 19 small slightly curved denticles on each side of cusp, sometimes bifurcated, commonly different in size. Lateral teeth narrow, slightly curved triangle blades, no denticulation traceable. Reproductive system diaulic. Ampulla long, narrow and convoluted. Vas deferens extremely long with slightly expanded prostatic part. Penis slightly folded, elongated when everted. Seminal receptacle absent.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF930744FF7E8C2AFE7F27CB.taxon	distribution	Distribution. Currently this species is known only from the Sea of Japan [Roginskaya, 1978; Martynov, 2013; Korshunova et al., 2017; this study], however further studies and sampling in adjacent regions are needed.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF930744FF7E8C2AFE7F27CB.taxon	discussion	Remarks. This species was described based on historical collections (sampling by the R / V “ Vityaz ” in 1972 – 1976) and materials from the SoJaBio expedition in 2010 [Korshunova et al., 2017]. The historical samples have been studied initially by Roginskaya [1978] and Martynov [2013], and were identified as either Coryphella stimpsoni or Coryphella japonica respectively. Furthermore, the collection of material suitable for the molecular studies allowed researchers to reconsider the deep-sea material of Z. japonica as a distinct species Z. abyssa [Korshunova et al., 2017], although sequences of true Z. japonica were not available for comparison. Our results support the distinct status of Z. abyssa from Z. japonica (Fig. 2 B), however our investigation of the radular morphology showed several differences with the original description of Z. abyssa (Fig. 7). Roginskaya [1978], Martynov [2013], and Korshunova et al. [2017] have reported on the irregular denticulation or even smooth rachidian teeth. Roginskaya [1978] suggested that the high variability in denticulation of lateral and rachidian teeth was a result of radular wearing. Martynov [2013] identified asymmetrically effaced rachidian teeth and also suggested this was a result of feeding on burrowing sea anemones of the family Edwardsiidae. Korshunova et al. [2017] considered the irregular denticulation of the rachidian teeth to be a specific trait differentiating Z. abyssa from the remaining species of the genus. According to the latter authors, denticles of the rachidian teeth are commonly “ fold-like or fork-like ”, sometimes greatly irregular, and the larger denticles are typically intermingled with the smaller ones, which is an obvious trait of studied juvenile specimen [Korshunova et al. 2017: 20, fig. 12 I]. In our material the denticles on the rachidian teeth were not highly irregular (Figs 7 F, H, J), but in several specimens their size was different and some of denticles were branched (Fig. 7 D). We did not detect any specific pattern of denticulation, like regular intermingling of larger denticles with smaller ones. Also, the anterior teeth rows had the same denticulation as the posterior teeth, with no sign of teeth wearing. Moreover, Korshunova et al. [2017] described small denticles on internal edge of the lateral teeth, however the referred figures display either only rachidian teeth [Korshunova et al., 2017: 20, figs 12 F – H] or smooth lateral teeth [Korshunova et al., 2017: fig. 12 E]. In our material the lateral teeth were smooth with no evidence for any denticulation (Figs 7 C, G, K). Ziminella abyssa is clearly different from other described species considered distinct herein. The main differences are observed in radular characters, as this species has the highest number of denticles on the rachidian teeth among Ziminella, and these denticles commonly have different sizes. Also, in our material smooth lateral teeth were detected, which could be another distinctive feature of this species. It is possible that the coloration or some external features could be also different from those in other Ziminella species, but we do not have newly collected material to confirm this. It is important to notice that both Martynov [2013] and Korshunova et al. [2017] identified a 2 mm specimen (ZMMU Op- 264) to be a member of Ziminella abyssa. This specimen has very distinct rachidian teeth with narrow and long central cusps, highly protruding from the tooth surface [Korshunova et al., 2017: fig. 12 I]. This morphology is not typical for Ziminella, but is found in other Paracoryphellidae, such as Chlamylla intermedia (Bergh, 1899), Paracoryphella parva (Hadfield, 1963), Polaria polaris (Volodchenko, 1946), see for example Korshunova et al. [2017], although no records of these species are known for the deep-sea waters of the Sea of Japan. We have studied a ‘ juvenile’ specimen from the Sea of Japan collected from 3427 – 3431 m in depth (MIMB 49484). The external appearance of this specimen (Fig. 8 A) is very similar to that of the ‘ juvenile’ ZMMU Op- 264 [Martynov, 2013: pl. 2.9], in particular they have similar body width and arrangement of oral tentacles and rhinophores; the bases of the rhinophores are closely together (Fig. 8 A), which is not typical for Ziminella (Fig. 3). The study of the radula of MIMB 49484 shows that it has similar morphology to that of Polaria polaris: the rachidian teeth are triangular and bear long central cusps, and the lateral teeth are wide with large sharp denticles on the inner edge and long cusp (Figs 8 B, C). Polaria polaris has a wide distribution in the Arctic waters [Martynov, 2006 as Coryphella polaris], and was also recorded from the Sea of Okhotsk and the southern Kuril Islands with a bathymetric limit of 325 m depth [Martynov et al., 2015]. Our discovery extends its geographical range to the Sea of Japan, and its bathymetric range to 3431 m depth. Taking into account the external similar- ity between MIMB 49484 and ZMMU Op- 264, and also the different radular morphology of the latter from typical Ziminella, we consider ZMMU Op- 264 does not belong to Ziminella abyssa. Nevertheless, we cannot precisely identify the species of ZMMU Op- 264 as its rachidian teeth morphology does not fit the diagnosis of any described paracoryphellid species. This fact, along with the discovery of P. polaris in the abyssal depths of the Sea of Japan, suggests the species diversity of this area is much higher than previously thought and further dedicated studies with comprehensive sampling for molecular analysis are needed.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF96075AFF0D8EFDFB72270F.taxon	description	(Figs 3 F, G, 6, 9 A – I, L, M)	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF96075AFF0D8EFDFB72270F.taxon	materials_examined	Type material. Lectotype (dissected): ZIN 24615, Sea of Japan, off Askold Is., 120 m depth, coll. Derzhavin, 25.06.1928 (designated by Martynov [2013]). Paralectotype ZIN 63758, dissected, same locality, depth and collector as in lectotype. Additional material studied: Sea of Japan, R / V “ Akademic Oparin ”, st. 80, 43 ° 18.7 ’ N 135 ° 10.0 ’ E, 219 m depth, coll. O. V. Chichvarkhina, 09.07.2021, MIMB 50759 (2 spm). Sea of Japan, R / V “ Akademic Oparin ”, st. 56, 44 ° 58.3 ’ N 136 ° 53.1 ’ E, 120 m depth, coll. O. V. Chichvarkhina, 04.07.2021, MIMB 50760 (1 spm). Sea of Japan, R / V “ Krasny Yakut ”, st. 119 / 4, 45 ° 05.3 ’ N 136 ° 56 ’ E, 115 m depth, coll. P. V. Ushakov, 10.07.1930, ZIN 63756 (1 spm). Sea of Japan, R / V “ Leitenant Dydymov ”, st. 431, 48 ° 08 ’ 30.0 ” N 140 ° 08 ’ 30.0 ” E, 122 m depth, coll. Soldatov, 15.09.1913, ZIN 63759 (1 spm). Type locality. Sea of Japan, off Askold Is., 120 m depth.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF96075AFF0D8EFDFB72270F.taxon	description	Description (based on studied specimens). External morphology: Body length up to 14 mm (preserved). Body wide. Foot wide, anterior corners short, rounded. Notal edge well-developed, continuous, elevations not extended above lateral body sides. Oral tentacles short, wide, conical. Rhinophores rugose, same size as oral tentacles, thinner than oral tentacles. Cerata in distinct rows, attached directly to well-defined notal edge. Cerata fusiform to cylindrical, lateral cerata much smaller than dorsal. Digestive gland diverticula filling from 1 / 3 to 3 / 4 of ceratal volume. Anal opening on right side right below notal edge, at beginning of posterior half of body. Reproductive opening on right side on anterior part of body. Coloration: Background body color pinkishwhite. Dorsal side of body lacking cerata, oral tentacles and rhinophores covered with extensive orange to reddish pigment, which becoming paler to peachy on tips of cerata and oral tentacles. Cerata orange-tan to deep red-brown, distal tip with white ring. Internal morphology (based on studied specimens): Jaws massive, oval-triangular with well-developed masticatory border bearing several rows of low blunt denticles or elevations. Radular formula: 17 – 28 × 1.1.1. Rachidian teeth massive, triangular. Central cusp strong, conical, elongated, non-compressed by adjacent denticles. From 6 to 11 small sharp and slightly curved denticles on each side of cusp, commonly from 7 to 9, denticles of about same size. Denticles may be ramified to 2 – 4 smaller denticles. Lateral teeth triangular plates, denticulation always present on first half. From 7 to 19 denticles on inner side. Reproductive system diaulic. Ampulla long, narrow and convoluted. Vas deferens extremely long with slightly expanded prostatic part. Penis conical or slightly folded. Seminal receptacle absent.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF96075AFF0D8EFDFB72270F.taxon	distribution	Distribution. The Sea of Japan from 115 to 528 m in depth [Martynov, 2013; Korshunova et al., 2017; present study]. Specimens with similar morphology are also known from the Sea of Okhotsk, the Southern Kuril Islands and from the British Columbia from depth of 20 m to 560 m (this study), but molecular data are needed for confirmation of their species identity (see below).	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF96075AFF0D8EFDFB72270F.taxon	discussion	Remarks. The type material (lectotype ZIN 24615) of Z. japonica was dissected and no slides of the radula and jaws of these specimens was available for study. At the same time, the original description provides the illustrations of the radular morphology [Volodchenko, 1941 b: pl. 4 - 1], which corroborates well with our morphological investigations. The external morphology of specimens collected from adjacent areas to the type locality and at the same depths (minimum distance ~ 250 km) corroborates with the initial description and the external morphology of the type material (see Volodchenko [1941 b]: pl. 3.3, and Martynov et al. [2013]: pl. 1.11, 1.12). Ziminella japonica shows several consistent differences with Z. abyssa and Z. salmonacea. Accordingly, Z. abyssa has more denticles on the rachidian teeth and shorter central cusps, and its lateral teeth are smooth and narrow (Fig. 7), while in Z. japonica laterals are triangular and bear small sharp denticles at first half of teeth (Fig. 9 D, G – I). Ziminella japonica differs from the Arctic-Atlantic species Z. salmonacea by the shape of the rachidian teeth (elongate-triangular in Z. salmonacea, while in Z. japonica they are clearly wider). Also, they show differences in the shape of lateral teeth (with narrow bases in Z. salmonacea, wide base in Z. japonica; in the former species lateral teeth are also slightly curved). The molecular analyses showed that Z. japonica from the Sea of Japan forms a separate clade, which is distinct from all other species of the genus (Fig. 2 B). Minimal interspecific differences were identified between Z. japonica and the North- Pacific bathyal species Z. vrijenhoeki (Table 1). Both these species are very similar morphologically. It was suggested that they differ in coloration [Valdés et al., 2018]. Although Valdés et al. [2018] compared Z. vrijenhoeki with specimens from British Columbia, which possess cream to pinkish coloration with white or beige cerata [Behrens, Hermosillo, 2005; Calder et al., 2015], true Ziminella japonica from the Sea of Japan has orange to reddish dorsum and dark rhinophores and cerata (Fig. 3 F, G). This coloration is different from both Z. vrijenhoeki and specimens of “ Z. japonica ” from British Columbia [Calder et al., 2015; Valdés et al., 2018]. There were also reports on different penial morphology of these species, as Z. vrijenhoeki has a folded penis, while it is conical in Z. japonica [Valdés et al., 2018]. Our results do not confirm this, since specimens from British Columbia have a folded penis (Fig. 3 H), and in the North-West Pacific Z. japonica the penis may have a different shape, and we suggest this is likely a result of tissue contraction during fixation. Although slight differences may be identified between radulae of these species, Z. japonica shows considerable variation in radular characters across the putative geographic range (Fig. 9). For instance, we have found a specimen (ZIN 63759, the Sea of Japan) in which denticles on the rachidian teeth were highly branched, making the denticles to be brush-like (Figs 9 E – H). We have also studied several specimens from the Sea of Okhotsk and the Kuril Islands (ZIN 63757, ZIN 63763, ZIN 63764, MIMB 15111, see Table S 1), which we initially identified as Z. japonica. Although most of them fit the diagnostic features of Z. japonica, a slight variation may be observed in external morphology (body length and shape, the extension of the notal edge). Also, some of these specimens show differences in radular morphology from true Z. japonica. For example, in specimen ZIN 63764 the rachidian teeth closely resembles those of Z. abyssa (more than 15 denticles and short cusp), but the lateral teeth were similar to those of Z. salmonacea (Fig. 9 J). Externally, the specimen ZIN 63764 has short extensions of notal edge, typical of Z. japonica. To sum up, although minor differences were found between Z. japonica and Z. vrijenhoeki based on the material from the type locality, the species status of Z. vrijenhoeki needs additional verification. We also cannot precisely identify several specimens collected outside the type localities, i. e. specimens from the Sea of Okhotsk, the Kuril Islands, and British Columbia, because no molecular data are available and the morphology and coloration of the living animals is unknown in most cases. Considering the slight variation of radular characters and coloration (e. g., creamy white specimens from British Columbia), we suggest Z. japonica could be either a species complex, or there is a single species with considerable intraspecific morphological and genetic variability as a result of wide geographical and bathymetrical distribution.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF88075BFC808E3AFD8A249E.taxon	description	(Figs 3 I, 6)	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF88075BFC808E3AFD8A249E.taxon	materials_examined	Type material. Holotype SIO-BIC M 12137, California, Monterey Bay, 36 ° 46 ’ 19.2 ” N 122 ° 04 ’ 58.8 ” W, 1018 m depth, 13.01.2007. Paratype SIO-BIC M 12135, California, Monterey Bay, 36 ° 46 ’ 19.6 ” N 122 ° 04 ’ 59.2 ” W, 595 m depth, 16.11.2009. Type locality. California, Monterey Bay, 36 ° 46 ’ 19.2 ” N 122 ° 04 ’ 58.8 ” W, 1018 m depth Detailed descriptions are provided by Valdés et al. [2018] and Ekimova et al. [2021 a]. No additional material was available for study.	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF88075BFC808E3AFD8A249E.taxon	distribution	Distribution. This species is known from the type locality [Valdés et al., 2018] and was further reported from the Bering Sea, at a depth of 660 m [Ekimova et al., 2021 a].	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
24370F05FF88075BFC808E3AFD8A249E.taxon	discussion	Remarks. Ekimova et al. [2021 a] have mistakenly reported on the presence of seminal receptacle, which is absent in all Ziminella. For now, the range limits of this species cannot be precisely determined as it shares several morphological similarities with Z. japonica and no additional material was available for morphological and molecular analysis. Further studies are needed to confirm the species validity of Z. vrijenhoeki and verify its geographical and bathymetric distribution (see Discussion).	en	Ekimova, Irina A., Stanovova, Maria V., Mikhlina, Anna L., Chichvarkhina, Olga V., Schepetov Corresponding, Dimitry M. (2025): A combination of historical collections and newly obtained molecular data contributes to the revision of the genus Ziminella (Nudibranchia: Cladobranchia). Ruthenica, Russian Malacological Journal 35 (2): 99-118, DOI: 10.35885/ruthenica.2025.35(2).5, URL: https://doi.org/10.35885/ruthenica.2025.35(2).5
