Costasiella vegae M. Ichikawa, 1993

Location: Kaminato, Hachijo Island, Tokyo, Japan
Date: 2019/06/15
Length: 6mm
Depth: 5.8m
Water temperature: 24.4℃

Description

Holotype 5 mm, paratypes 5-10 mm. Brown contiguous eyes sit between the bases of the rhinophores. The anterior corners of the foot are not extended. Rhinophores white with black tips. The white head bears a conspicuous red mark behind the eyes, shaped like a posteriorly pointing arrowhead. Cerata in 8 rows, all the same colour: green spotted with white dots; the distal portion of each ceras has many small red spots, increasing in density distally and eventually forming a red line, with white pointed tips. On the dorso-distal part of each ceras is an eye-like pattern — a white spot encircled by a dark green ring. In one paratype only a red line is present on the head.

Distribution

Type locality: between Uganzaki and Yarabuzaki on Ishigaki Island, 0.5-1 m deep on Avrainvillea erecta. Known from the Ryukyu Islands.

Etymology

The specific epithet is based on the name of Vega, the brilliant first-magnitude star in the constellation Lyra.

Remarks

Resembles Costasiella oculifera in colour but is separated by the eye-like pattern on the cerata, which is lacking in that species. Both share a conspicuous mark behind the eyes, but the shape and colour differ. Unlike its close congeners, the anterior corners of the foot do not protrude.