Dermatobranchus nigropunctatus Baba, 1949

ホソジマオトメウミウシ Dermatobranchus nigropunctatus

Location: Sentan, Osezaki, Shizuoka, Japan
Date: 2019/02/02
Length: 12mm
Depth: 7.0m
Water temperature: 16.0℃

Description

A relatively large Arminidae, body length 6-10 cm. The mantle is broad with wavy lateral margins. The dorsum bears 13-17 very fine longitudinal folds. Ground colour of the dorsum and body sides olive, with patches of dark shading. The head veil, mantle, and foot margins are all bordered by a fine vermilion line. Rhinophore lamellae brown to vermilion; the stalks white. The longitudinal folds on the dorsum form thin white lines, along which many fine black dots are arranged somewhat irregularly. The foot and foot margin also bear scattered small black spots. Gills pale yellow. Radula formula 30×40-42.1.40-42 to 35×50-55.1.50-55. The central tooth bears about 15 denticles on each side, the first lateral has 15-18 denticles, and the remaining laterals are smooth.

Distribution

Type locality combines three sites in Sagami Bay: Okinose (200 m depth, September 1936), off Hayaki at Sajima Island (16 m depth, July-August 1939 and August 1940), and Hayama-Najima (20 m depth, July 1931). The original description (Baba, 1949) records the species only from Sagami Bay.

Etymology

The specific epithet nigropunctatus is a Latin compound of niger (black) and punctatus (spotted), referring to the black fine dots arranged along the dorsal folds. The original description does not give an explicit etymology paragraph. The Japanese name "Hoso-jima-otome-umiushi" (fine-stripe maiden sea slug) reflects the fine longitudinal striping.

Remarks

Originally described as Dermatobranchus (Dermatobranchopsis) nigropunctatus in the subgenus Dermatobranchopsis (later treated by Baba himself as a junior synonym of Pleuroleura Bergh, 1874). Diagnosed by the combination of 13-17 fine longitudinal dorsal folds and the row of black fine dots along each fold.