Coryphella alexanderi sp. nov.

(Figs 2–4)

ZooBank registration: urn:lsid:zoobank. o rg: a c t: E 4 9 D 9 E 1 E ­ 7 8 F 7 ­ 4 4 E E ­ A B 8 9 ­ 11D75A1B955F

Type material. Holotype MIMB42468, partly dissected, radula and jaws mounted on SEM stub . Paratypes: MIMB42469, three specimens, two dissected, same locality and collector as holotype. ZMMU WS14380, one specimen, dissected, northern Kuril Is., coordinates not available, 10­20 m depth, 04.08.2016, coll. Alexander Semenov.

Type locality. Sea of Okhotsk, Urup Is., 46°17.0’N, 150°17.0’E, 148–198 m depth, 05.07.2019, coll. Anastassya Maiorova.

Description. External morphology (Fig. 2). Body length up to 22 mm. Body narrow, tapering to tail. Rhinophores about two times longer than oral tentacles. Rhinophores smooth with thin wrinkles. Anterior foot corners present. Notal edge reduced, discontinuous. Cerata in continuous rows, not united in separated groups. Anus pleuroproctic. Reproductive opening on right side under anterior ceratal rows.

Coloration (Fig. 2). Background color of body translucent milky­white. Dorsal side of oral tentacles with opaque white pigment dots. Opaque white line on back side of rhinophores, becoming pigment white band on rhinophoral tip. Tail with white line. Digestive gland diverticula inside cerata from orange to pale brown. Cnidosac area white, with thin, white pigmen band.

Табл. 1. Минимальные меЖвидовые нескорректированные p- дистанции по гену СОI меЖду Coryphella alexanderi sp. nov. и другими видами рода Coryphella .

Coryphella amabilis 12.61 Coryphella athadona 12.09 Coryphella borealis 7.94 Coryphella browni 7.77 Coryphella chriskaugei 9.15 Coryphella gracilis 12.44 Coryphella falklandica 16.75 Coryphella lineata 6.74 Coryphella monicae 10.71 Coryphella nobilis 10.36 Coryphella orjani 9.50 Coryphella sanamyanae n/a Coryphella trilineata 12.95 Coryphella trophina 9.33 Coryphella verrucosa 11.92

Internal morphology (Figs 3, 4). Jaw triangle plate with strong masticatory process (Fig. 3A). It bears at least 9 rows of small denticles (Fig. 3B). Outer denticles simply serrated, especially on masticatory edge (Fig. 3C). Radular formula: 15–17 x 1.1.1 (Fig. 3D, H). Rachidian tooth triangular, with long sharp cusp, and 5–9 large sharp denticles on each side. Cusp usually longer than denticles. Lateral teeth widened, triangular, with attenuated outer basal processes and up to 14 denticles on inner side. Reproductive system diaulic (Fig. 4). Ampulla large, folded. Vas deferens of moderate length, widened in proximal prostatic part. Distinct distal and proximal receptaculum seminis, both small muscular sacs. Penis broad, conical.

Distribution. This species is only known from the middle and northern Kuril Islands.

Ecology. This species has a wide bathymetric range, being found in both upper (10–20 m in depth) and deep (down to 200 m in depth) shallow waters, and it is very likely it inhabits intermediate depths as well. In upper shallow­water it was found on Rhizorhagium roseum M. Sars, 1874 and Eudendrium sp. (Fig. 2A).

Remarks. Both morphological and molecular analyses support the distinctiveness of Coryphella alexanderi sp. nov. from other species in the genus. The external morphological characters of this new species shows the most resemblance to the North­West Pacific species Coryphella sanamyanae, the amphiboreal species C. nobilis A. E. Verrill, 1880, and the North-East Atlantic species C. browni, as it possesses continuous rows of cerata, reddish color of the digestive gland diverticula, and white rhinophores. However, Coryphella alexanderi sp. nov. differs from all these species by internal anatomical features. First of all, it differs in radular characters, since in C. nobilis and C. sanamyanae the rachidian tooth possesses a very small central cusp that is usually compressed. Coryphella browni has narrower lateral teeth with small cusps and tiny denticles; this species also possesses a single row of denticles on the masticatory edge of the jaws, while in C. alexanderi sp. nov. there are at least 10 rows of serrated denticles. From other species of the genus Coryphella inhabiting the North­West Pacific, C. alexanderi sp. nov. differs by its external morphology. From C. verrucosa and C. amabilis it differs by having the cerata arranged in continuous rows (in groups in C. verrucosa and C. amabilis), from C. trophina by having almost smooth rhinophores (perfoliated in C. trophina); Coryphella athadona and C. abei possess a Y­marking on head, that is absent in C. alexanderi .

Etymology. This species is named after my beloved farther Alexander V. Ekimov, who passed away during the preparation of this manuscript.Alexander V. Ekimov was a researcher in the field of high energy physics, his passion for his work inspired me to become a scientist and his support always encouraged me to be fully dedicated to my research. He will be greatly missed.