Gymnodoris amakusana (Baba, 1996)

Location: Wannai, Osezaki, Shizuoka, Japan
Date: 2017/02/06
Length: 10mm
Depth: 8.0m
Water temperature: 16.0℃

Description

Body length up to 35 mm. Ground colour translucent white. The dorsum is marked off from the sides by a ridge (notal ridge) that is absent in the genus Gymnodoris. The 10-11 gills are simply pinnate or bilamellate: the main rachis of each plume is bilaterally provided with 2-5 lamellate pinnae. The genital orifice lies on the right antero-lateral side of the body; the oral tentacles are lobiform. The notal ridge is completely bordered with a rich golden yellow line which turns behind the gills into a lateral golden yellow line extending as far as the head. A transverse bar of the same colour is always present just in front of the gills. Each gill is golden yellow terminally and translucent white basally. The rhinophores are white on the stalk and deep golden red on the club. The tail is golden yellow medially. The foot is white margined with golden yellow.

Distribution

Type locality: Notojima, Toyama Bay, Japan. Records also from Amakusa, Toyama Bay (Sarushima, Notojima) and the Inland Sea of Seto, as well as Hong Kong and Queensland, Australia.

Etymology

The specific name amakusana (original spelling amakusanum) is derived from Amakusa (Kumamoto Pref.), the locality where the species was first collected — not from the type locality of the holotype (Notojima, Toyama Bay).

Remarks

Originally described as Analogium amakusanum, the type species of the new genus Analogium. The Amakusa specimens had earlier been identified as Gymnodoris striata, but the redescription of the type material of Analogium striatum revealed stable colour-pattern differences (notably the double golden lines on the mantle margin and the golden transverse bar just in front of the gills), and this material was therefore separated as a new species. Analogium was subsequently sunk into Gymnodoris, giving the current combination.