Thuridilla gracilis

Thuridilla gracilis is a species of sea slug, a sacoglossan, a marine gastropod mollusk in the family Plakobranchidae.

Distribution

Tropical Indo/West-Pacific.

This sea slug lives on external slope of coral reef, on top of the reef and in the lagoon, usualy meet in shallow water.

This species can be up to 25 mm in size.

The body is stretched and partially covered by the fold of the lateral parapodia.

The mantle is black and crossed by multiple fine white longitudinal lines (eight to ten) punctuated sometimes with blue spots.

The border of the lapel of the parapodia and rhinophores is often orange.

The smooth Rhinophore can be whitish without any lines.

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

Thuridilla gracilis has a diet based on algaes.

P.L. Beesley, G.J.B. Ross & A. Wells,"Mollusca-The southern synthesis", vol.5,CSIRO,1998,ISBN 0-643-05756-0
David Behrens, "Nudibranch behaviour", Newworld Publication INC., 2005, ISBN 978-1878348418
Gary Cobb & Richard Willan, "Undersea jewels- a colour guide to nudibranchs", Australian Biological Resources Study, 2006, ISBN 0642568472