Slender Roboastra

Roboastra gracilis is a species of sea slug, a polycerid nudibranch, a marine gastropod mollusc in the family Polyceridae.

Description

Robastra gracilis is a relatively small nudibranch reaching only 20–25 mm (2-2.5 cm) in length. Characterised by the yellow longitudinal lines which are sometimes quite onscure. These lines consist of a series of glandular pits which secrete a bright yellow substance when disturbed.

Body is elongate and limaciform with a long and pointed posterior end of the foot. The ground colour of the body is blue-black with yellow-orange longitudinal lines, which can be continuous or discontinuous. The proportionally large rhinophores and gills are a very characteristic feature of this species. They can be deep blue, blue-grey or purple depending on the specimens.

Distribution

This sea slug is found in the tropical western Pacific Ocean.

Habitat

This species is a member of a genus which hunts down and eats other opisthobranchs. The large oral tentacles are found in all members of Roboastra and are probably important in tracking down their prey, perhaps by following its mucus trail.