Elysia expansa

O’Donoghue, 1924

Elysia expansa

Elysia is a member of the family Plakobranchidae along with Thuridilla and Plakobranchus. Plakobranchids feed primarily on green algae, but also diatoms. They have a pair of elongate parapodia and do not possess cerata.

The body is usually yellowish-green in colour, with a narrow, dark reddish or black margin down the parapodial. On the outside of the papapodia are small, conical papillae. They are associated with the green algae Caulerpa brownii and Caulerpa remotifolia.

I have encountered them at Bare Island at depths of 12-15m and around 50-80mm in size.