Elysia timida (Risso, 1818)

Description

A small sacoglossan, reaching about 10 mm in length, and the type species of the genus Elysia. The body is short and broad, with rather thick, upright parapodial flaps. Ground colour is a clear green, often with opaque white pigment on the head, the parapodial margins and a mid-dorsal ridge. Small red spots are scattered over the body, but characteristically absent from the inner surface of the parapodia. The rhinophores are white to pale white.

Distribution

Type locality: Nice, France (north-western Mediterranean). The species occurs throughout the Mediterranean and along the north-east Atlantic (Portugal, Canary Islands, Madeira, Azores). Reports from the Caribbean also exist, although the distributional limits are still debated. It inhabits the lower intertidal and shallow rocky habitats.

Etymology

The specific epithet timida is the feminine form of Latin timidus ("timid, cautious"). The original description gives no explicit reason, but the name has been interpreted as referring to the habit of quickly closing the parapodial flaps when disturbed.

Remarks

Elysia timida is the type species of Elysia Risso, 1818 and is widely used as a model species in research on sacoglossan kleptoplasty. It feeds on the green alga Acetabularia acetabulum, sequestering its chloroplasts in the digestive-gland branches and maintaining them functional for several months.

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References

• Elysia timida (Risso, 1818) — type species, Risso A. (1818). Mémoire sur quelques Gastéropodes nouveaux, Nudibranches et Tectibranches observés dans la mer de Nice. Journal de Physique, de Chimie, d'Histoire Naturelle et des Arts. 87: 368-377.