Cadlina umiushi Korshunova, Picton, Sanamyan & Martynov, 2015

Description

A small Cadlinidae, holotype body length 10 mm live. Notum broad, rounded in front and posteriorly. Rhinophores long and retracted into raised soft sheaths bearing small tubercles, 11-18 rhinophoral lamellae. Notum covered with distinct, small, rounded tubercles, with spicules forming a sparse network. Six to eight multipinnate gills united by a common membrane into a circle around the anus and retractable into a common gill cavity, the cavity border moderately raised with a tuberculated edge. Oral veil small, trapezoid, with oblique notched lateral sides. Foot broad, anteriorly rounded and slightly thickened to form a double edge. A yellow line bordering the notum is always well defined, distinguishing the species externally from the usually-white Cadlina laevis.

Distribution

Holotype ZMMU Op-445 (10 mm live), NW Pacific, Russia, Sea of Japan, Peter the Great Bay, Bolshoi Pelis Island, on stones, 5-7 m depth, 7 September 2014 (collectors T. A. Korshunova, A. V. Martynov). Paratypes from Spokoinaya Bay (20 m, stony/rocky substrate) and Vostok Bay (5-7 m, stones with algae). Subsequent integrated molecular and morphological analysis established Cadlina olgae as a junior synonym; the distribution likely extends across the Sea of Japan.

Etymology

The specific epithet umiushi is derived from the Japanese vernacular word "umiushi" (海牛, sea slug); the use of a Japanese vernacular as a Latinised specific name is unusual. The Japanese name "Koburi-cadlina-umiushi" (small Cadlina sea slug) reflects the species' small size within the genus.

Remarks

A later Cadlinidae monograph established Cadlina olgae as a junior synonym. The lowest COI interspecific distance is 3.9% to the North Atlantic C. laevis, and 4.7% to the sympatric Pacific C. kamchatica. C. umiushi is externally similar to a rare yellow-bordered colour form of C. laevis, but the yellow notum border is always clearer and more pronounced in C. umiushi.

---

References

• カドリナ・ルテオマルギナータ, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
• カドリナ・ルテオマルギナータ, 小野篤司 & 加藤昌一. (2009). ウミウシ. 誠文堂新光社.
• Martynov A.V., Sanamyan N.P. & Korshunova T.A. (2015). Review of the opisthobranch mollusc fauna of Russian Far Eastern seas: Pleurobranchomorpha, Doridida and Nudibranchia. Bulletin of Kamchatka State Technical University, 34, 62-87. https://doi.org/10.17217/2079-0333-2015-34-62-87
• コブリカドリナウミウシ（新称）, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Korshunova T., Fletcher K., Picton B., Lundin K., Kashio S., Sanamyan N., Sanamyan K., Padula V., Schrödl M. & Martynov A. (2020). The Emperor’s Cadlina, hidden diversity and gill cavity evolution: new insights for the taxonomy and phylogeny of dorid nudibranchs (Mollusca: Gastropoda). Zoological Journal of the Linnean Society. DOI: 10.1093/zoolinnean/zlz126/5741605.