Onchimira cavifera Martynov, Korshunova, N. Sanamyan et K. Sanamyan, 2009

Ekimova, Irina A., Grishina, Darya Yu. & Nikitenko, Ekaterina D., 2024, Nudibranch molluscs of Sakhalin Island, Northwestern Pacific: new records and descriptions of two new species, Ruthenica, Russian Malacological Journal 34 (2), pp. 69-91 : 80

Onchimira cavifera Martynov, Korshunova, N. Sanamyan et K. Sanamyan, 2009

( Fig. 7A)

Material studied: MIMB48048 , 1 specimen, dissected, the Sea of Okhotsk , Severny Bay, 54°31.5’N, 140°44.7’E, 80–82 m in depth, 31.07.2019, coll. A. Mayorova.

Diagnosis: Length 16 mm. Notum semitransparent white, rounded in front and posteriorly. Notum wrinkled, soft, with slight elevations and low tubercles. Eight rhinophoral lamellae, rhinophoral sheath lacking tubercles. 13 branchial leaves surrounded by low gill cavity. Radular formula: 24 x 6.1.6. Rachidian tooth subulate, smooth. Lateral teeth large beak-shaped, smooth. Marginal teeth elongated plates. Reproductive system was not study due to bad fixation.

Molecular data: A BLAST-n search of COI sequence resulted 97.12% identical to 2 sequences of Onchimira cavifera from GenBank (including the paratype ZMMU:Lc-37449, MN224073). On the phylogenetic tree ( Fig. 6) our specimen also forms a single clade with O. cavifera from GenBank (PP = 1; ML = 100).

Distribution: This species was described from the North-West Pacific, Starichkov Is., Kamchatka, 18–26 m in depth [ Martynov et al., 2009], and subsequently reported from the same locality [ Hallas et al., 2017]. Its discovery off Sakhalin Is. expands its known geographic and bathymetric range to the southwestern Sea of Okhotsk at 82 m in depth, suggesting this species could be found in other localities of this sea.

Remarks: Although the external and internal morphology of our specimen matches the original description of O. cavifera [ Martynov et al., 2009], genetic data show slight differences (p- distance = 2.7%) in the COI marker between specimens from the Sea of Okhotsk and Kamchatka, suggesting restricted geneflow between these localities. Further studies are needed to test species limits across the geographical range of O. cavifera .