Onchidoris muricata (O. F. Müller, 1776)

Description

A small dorid reaching about 14 mm in body length. Ground colour is white to pale yellowish-white. The dorsum is densely covered with wart-like tubercles, each in turn coated with minute caryophyllidia (small velvety papillae), giving the body a rough texture overall.

The rhinophores are short, lamellate and the ground colour. The gill consists of 8-12 simply pinnate, translucent plumes arranged in a circle on the posterior dorsum. The species is typically found pressed against rocky reef walls.

Distribution

A boreal-Arctic species widely distributed across the North Atlantic, Arctic Ocean and North Pacific. Recorded from Iceland, Greenland, Norway, the North Sea, the British Isles, France, Russia, the United States (Alaska, Maine), Canada and Japan (Hokkaidō to the Pacific coast of northern Honshū).

Etymology

The specific epithet muricata is the feminine of Latin muricatus ("pointed, prickly"), in reference to the dense, pointed dorsal tubercles.

Remarks

The genus Onchidoris Blainville, 1816 comprises bryozoan-feeding dorids. Onchidoris muricata is most commonly found on encrusting bryozoans such as Membranipora membranacea. Egg masses are yellow to orange ribbons coiled in a spiral.

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References

• Onchidoris muricata, Blainville H.M.D. de (1816). Quatrième mémoire sur les mollusques, de l'ordre des Cyclobranches. Bulletin des Sciences, par la Société Philomathique de Paris. 1816: 93-97.
• シロトゲウミウシ（新称）, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Onchidoris muricata, Behrens D.W., Hermosillo A., Fletcher K. & Jensen G.C. (2022). Nudibranchs & Sea Slugs of the Eastern Pacific. Molamarine.