Orange-Edged Sapsucking Slug

Thuridilla lineolata is a species of sea slug, a sacoglossan, a marine gastropod mollusk in the family Plakobranchidae. It is an Indo-Pacific species that lives in or near coral reefs and eats algae.

Description

This species can be up to 3 cm in size. The body is partially covered by the fold of the lateral parapodia. The mantle is bright blue, and the edges of the parapodia are framed by two lines: a fine black one and an orange one on the external side.

The smooth rhinophores and the oral cavity are also marked with a black line and with an orange band.

It is very similar in colour to Thuridilla undula the main difference being that the parapodial margin is very undulating, the inner border between the orange and black margin and the inner blue region forming a sinuous line.

Distribution and habitat

This species occurs in the tropical West-Pacific, mainly in Indonesia and the Philippines. It lives on the external slope of coral reefs, on top of the reef, and in the lagoon.

Biology

This species is benthic and diurnal. Because of its aposematic coloration, it crawls around to feed in the daylight. Its diet is based on algae.