Nella soboli (Martynov, 1992)

Description

A small cold-water aeolid with a translucent yellowish-white body and elongate, thick dorsal cerata. The body is moderately wide with a broad foot and tail; the oral tentacles and rhinophores are similar in length, smooth to slightly wrinkled. The cerata are arranged in up to six pre-anal rows, with the anal opening positioned lateral to the cerata. Inside the cerata the digestive gland varies from light brownish or sandy to dark brown, and the basal portion is usually darker. White spots or streaks are scattered along the outer ceratal surface, and the tips of the cerata are colourless or dusted with white pigment. The rhinophores are semi-transparent to light yellowish or orange-ochre, with dispersed white pigment near the tip. The holotype reached about 30 mm in live length.

Distribution

Originally known from Sobol Bay on the Russian coast of the Sea of Japan. Subsequent records extend to Spokoinaya Bay (Sea of Japan, Russia) and the central to southern Kuril Islands, including Natalya Bay on the Okhotsk side of Urup Island; the species is also expected to occur along the coast of Hokkaido. It inhabits the intertidal to about 10 m depth on stones, rocks and rubble bottoms.

Etymology

The specific epithet soboli refers to the type locality, Sobol Bay in the Sea of Japan.

Remarks

A cold-water specialist whose reproduction takes place in winter. Development is direct or via a strongly abbreviated planktonic stage, both interpreted as adaptations to a boreal habitat. The diet is not fully resolved, but the species is thought to feed on hydroids.

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References

• Cuthonella soboli sp. n., Martynov A.V. (1992). A new species of nudibranch molluscs of the Sea of Japan with notes on the genus Cuthonella (Gastropoda, Opisthobranchia) [in Russian]. Zoologicheskii Zhurnal. 71(12): 18-24.
• Cuthona sp. 19, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
• ソボルイミノウミウシ, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Cuthonella soboli, Korshunova T.A., Sanamyan N.P., Sanamyan K.E., Bakken T., Lundin K., Fletcher K. & Martynov A.V. (2020). Biodiversity hotspot in cold waters: a review of the genus Cuthonella with descriptions of seven new species (Mollusca, Nudibranchia). Contributions to Zoology. 90(2): 216-283. https://doi.org/10.1163/18759866-bja10017
• Nella soboli (Martynov, 1992) comb. nov., Martynov, A. & Korshunova, T. (2025). Hidden diversity of the North Pacific prompts reorganization of the taxonomic system. Moscow: Neptune. ISBN 978-5-9905149-3-5. 48 pp.