has a delicate leaf-shaped body up to 5 cm in length which tapers posteriorly. This species is commonly vivid green, and occasionally bright red or brown. Tiny glistening red, blue or green spots are also present. Both body length and colour are determined by diet. White patches may be found on the edges of the projections of the foot (parapodium) and around the eyes, and black markings may sometimes be present on the head and body. The parapodium is broad, with lobed or frilled edges and extends almost the entire length of the body, containing visible green chloroplasts. Lateral parapodial "wings" may be outstretched or held over the body. The head bares conspicuous propodial tentacles and a pair of enrolled rhinophores that open ventrally and usually have white distal ends (anus present under right rhinophore). Digestive diverticula which contain ingested chloroplasts, ramify and can be visible through the surface of the body, parapodia and rhinophores.Elysia viridis
is very similar to the sea hare in its soft winged body and colouration, although Elysia
sp. is flatter with no oral tentacles. Elysia viridis
is known as a 'sap-sucking slug' and feeds only on a single or limited food source (stenophagous). It ingests the chloroplasts unharmed and uses them for photosynthesis which benefit the slugs food supply (a process known as klepoplasty). Chloroplasts account for the colouration of the animal.
This species has a 12-15 month life-span and is sexually mature when 1.2 cm in length. It produces benthic egg masses from April to October which hatch as planktonic veligers. This species may also tolerate low salinity levels.