Sap-Sucking Slug

Adult length of E. viridis ranges between 15 and 20 mm, with a healthy adult weight of 15–20 mg. The surface of the slug is covered in tiny spots of red, yellow, blue or green that are reported to have a glistening appearance. Parapodia extend from the sides of the slug, and are the main location of captured chloroplasts. Rhinophores extend upward from its head. Elysia viridis feed using radular teeth, which in this species, E. gordanae, can vary in design based upon the diet of the individual.

Elysia viridis is located in the Northeastern Atlantic, primarily around the British Islands, but has been found further north in Sweden and Norway, as well as in the Mediterranean Sea. A report of E. viridis being found in south Africa was published in 1987, but the identification that specimen was later changed to Elysia sp. by the same author. Elysia viridis occurs in the intertidal zone typically submerged on its algal prey between 1 and 5 meters below the surface.

Elysia viridis feed on algae, primarily of the genus Codium, with a noted favorability towards C. fragile, C. sericea, and C. rupestris. E. viridis has been found to be less selective of algal hosts than other members of Elysia. E. viridis deposit coiled egg masses onto the thallus of its prey, or on nearby underwater surfaces, that hatch into a larval stage called a veliger. Veliger are planktotrophic and consume free floating unicellular algae. Once the propodeum develops on the larvae they search for a macroalgal host, contact with which appears to trigger a metamorphosis into the adult form, but the trigger for this metamorphosis is unconfirmed.