Diaulula odonoghuei (Steinberg, 1963)

Location: Shakotan, Hokkaido, Japan
Date: 2025/04/13
Length: 50mm
Depth: 10.0m
Water temperature: 7.0℃

Description

Ground colour grey-white to pale yellowish-brown, the dorsum scattered with chocolate-brown spots that may be ring-shaped or solid and vary considerably in size. A diagnostic feature is that these spots extend onto the mantle margin. The dorsum is finely villous, giving a velvety texture. Rhinophores and gills are pale yellow to off-white; the branchial plume comprises around six tri- to quadripinnate leaves. This is one of the larger species of Diaulula, reaching about 100 mm in length.

Distribution

North Pacific. The neotype was collected at Gig Harbor, Washington, USA. The species has an amphi-Pacific range extending from Korea and northern Japan (south to Onagawa) through Hokkaido, the Aleutian Islands and the Pacific coast of North America southwards to Bodega Bay in northern California, predominantly in cold-water regions.

Etymology

The specific epithet odonoghuei honours Charles Henry O'Donoghue, the British-born Canadian zoologist who studied the nudibranch fauna of the Vancouver Island region in the 1920s. O'Donoghue had originally described populations belonging to this species as Doris echinata O'Donoghue, 1922, but that name was a junior homonym and unavailable; Steinberg 1963 later proposed Doris odonoghuei as a replacement name dedicated to him.

Remarks

This species was long confused with the broadly North-Pacific Diaulula sandiegensis (J. G. Cooper, 1863), and Japanese animals were treated under the latter name. Hallas, Simison & Gosliner 2017, combining molecular phylogenetics with morphology, recognised two species: a "spotted" form with spots reaching the mantle margin (D. odonoghuei) and a "ringed" form lacking marginal spots (D. sandiegensis). Northwest-Pacific populations previously called the ezo leopard dorid are referable to D. odonoghuei. The species feeds on sponges. the 1957 study recorded it as D. sandiegensis from northern Japan (Akkeshi, Muroran, Shirikishinai, Asamushi and Onagawa), proposing the Japanese name "Ezo-kasuriumiushi".