Dirona pellucida Volodchenko, 1941

Description

The body is bright orange to reddish-orange, sprinkled with fine white granular spots over the dorsum and the foot.
Densely set spindle-shaped cerata cover the back; each ceras carries a white margin and tapers to a white tip. White granules are scattered along the cerata as well.
The rhinophores and oral tentacles share the orange ground color and are also dusted with white granules.
Large individuals reach 100–120 mm in length.

Distribution

Far-eastern coast of Russia (type locality), the Bering Sea, Alaska, Canada and the U.S. west coast (south to Coos Bay, Oregon), the Sea of Japan, South Korea, and northern Japan including Akkeshi Bay, Hokkaido. Widely distributed across the cold-water North Pacific.

Etymology

From the Latin pellucidus meaning "transparent" or "translucent", referring to the somewhat translucent appearance of the type material.

Remarks

A bryozoan-feeder, with Bugula pacifica reported as a principal prey item; feeding on hydroids has also been recorded.
The species has a tangled nomenclatural history rooted in the wide North Pacific range. Volodchenko 1941 described Dirona pellucida from the Russian Far East. Baba 1935 reported Akkeshi Bay specimens as the North American Dirona albolineata, but a 1957 study by Baba reassigned them to a replacement name, Dirona akkeshiensis Baba, 1957 (n. n.), on the grounds that the Akkeshi animals lack the white edging of D. albolineata and are uniformly pinkish-orange. Hurst 1966 then described Dirona aurantia from the Pacific North American coast. Re-examination of Volodchenko's material by Martynov 1997 showed that all three names refer to the same species, leaving Dirona pellucida as the senior valid name.

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References

• Dirona pellucida n. sp., Volodchenko N.P. (1941). New species of the nudibranchiate molluscs from the Far-Eastern seas of USSR. Issledovaniya Dalnevostochnykh Morei SSSR. 1: 53-68.
• Dirona akkeshiensis Baba, n. n. Akebono-umiushi (n. n.), Baba, K. 1957. A revised list of the species of Opisthobranchia from the northern part of Japan, with some additional descriptions. J. Fac. Sci., Hokkaido Univ.,ser. 6, Zool. 13(1-4):8-14.
• Dirona pellucida, Behrens D.W., Hermosillo A., Fletcher K. & Jensen G.C. (2022). Nudibranchs & Sea Slugs of the Eastern Pacific. Molamarine.