Elysia timida

Elysia timida is a species of mollusc belonging to the class Gasteropoda, family Plakobranchidae, which together with 101 other species make up the genus Elysia. Long considered a species endemic to the Mediterranean Sea, sightings of Elysia timida have recently been reported from Cuba, the coast of Florida and Cape Verde, where it is believed to have been accidentally introduced. It generally inhabits shallow waters with large amounts of algae, especially Acetabularia acetabulum and Padina pavonica.

The body of Elysia timida can reach up to 2 cm in length. It is whitish in color, with the dorsal part of the body green and small red dots distributed throughout its body. The head, which is elongated, has two long oral tentacles, behind which are the rhinophores, which in this species are coiled and relatively thin. At the base of the rhinophores we can observe the black eyes. From the sides of the body arise the parapodia, which run from the end of the head area to the tail, adopting a triangular shape.

The diet of Elysia timida consists of algae, and during the summer months its diet consists almost exclusively of specimens of the unicellular alga Acetabularia acetabulum, while in early autumn they feed predominantly on the alga Padina pavonica. A curiosity in the feeding of these nudibranchs is that they are able to isolate the chloroplasts of the algae on which they feed, and keep them in a functional form in their own tissues. This fact is responsible for the green coloration of the back of the specimens, since it is there where the chloroplasts of the algae on which they feed accumulate. Not only this, but the accumulation of functional chloroplasts in their tissues allows them to obtain energy from the photosynthesis carried out by these organelles.

As for the reproduction of Elysia timida, the specimens are hermaphrodites and have a reciprocal mating by which both individuals exchange sperm to fertilize their eggs. This reproduction process follows a ritual dance by which the individuals initially position themselves face to face, and then slide down each other's right flanks to exchange sperm. Reproduction usually takes place during the spring months, at which time they will lay their eggs forming white spirals of approximately 1 cm in diameter.