Coryphella athadona (Bergh, 1875)

Location: Beach, Oyashirazu, Niigata, Japan
Date: 2020/03/10
Length: 6mm
Depth: 5.0m
Water temperature: 10.0℃

Description

A small flabellinid reaching 16 mm in length. The body is translucent white, with a single white line running along the dorsal midline from back to tail and sparse white specks across the body surface. The cerata show the orange-red digestive gland through the translucent wall and end in white tips. The rhinophores are smooth and long, coloured like the body, with fine white specks on the distal half. The oral tentacles are also smooth, with fine white specks arranged in a line.
Externally distinguished from the sympatric Coryphella amabilis by the presence of a white longitudinal line on the dorsum (C. amabilis lacks this line).

Distribution

The type locality is the Sea of Japan (around 39°40′-40°N, 133°30′-134°E), based on the original description by Bergh (1875). Baba (1935, 1957) subsequently reported the species from Mutsu Bay, Akkeshi Bay (Akkeshi and Daikoku-shima), Asamushi, Shirikishinai, and Osyoro. The species is regarded as a cold-water endemic associated with the Oyashio Current region of northern Japan.