Aplysiopsis nigra (Baba, 1949)

Location: Futou beach, Tago, Futou, Dougashima, Shizuoka, Japan
Date: 2017/12/21
Length: 30mm
Depth: 8.0m
Water temperature: 16.0℃

Description

An entirely black sacoglossan, body length 12-30 mm, with a body shape similar to that of the sympatric Aplysiopsis orientalis. The cerata are circular in cross-section, with few indistinct lamellate ridges on the inner face and a smooth outer face; arranged in about 25 oblique rows per side, each row of 3-4 cerata, with branching liver diverticula. The body is black overall, with a black-brown rhizome. A small white area surrounds each eye, from which a narrow same-colour zone extends upward to the rhinophore tip; the rhinophores, oral tentacles, and foot margins are also fringed white. The cerata are black with a white dorsal vein. Radular ascending row 5 teeth, descending row about 40 teeth, with the distal end of the descending row markedly coiled.

Distribution

Type locality is off Nishi-no-saki, Sagami Bay (500 m offshore, 10 m depth, April 1941, 3 specimens). The original description (Baba, 1949) records the species only from Sagami Bay.

Etymology

The specific epithet nigra is Latin for black. The original description does not give an explicit etymology paragraph; the descriptive sense reflects the uniformly black body colour.

Remarks

Originally described as Hermaeina (Hermaeina) nigra and later transferred to Aplysiopsis. The sister species Aplysiopsis orientalis (yellow-white ground with brown longitudinal stripes) is readily separable from the uniformly black ground with white facial markings of this species.