The green sapsucking slug is variable in color, from green to red, depending on the algae it is feeding on. It is covered in bright bluegreen speckling and the rhinophores tend to be dark brown to black. The parapodial margins can have white edges and the digestive gland can be visible through the body wall.
Unassessed by the IUCN Red list, but commonly seen in the NorthEast Atlantic.
They can be found from the Eastern Atlantic, Northern Europe and parts of the Western Indian Ocean, the Mediterranean. The prefer to be in shallow, temperate or subtropical water where light still penetrates the water column and algae and weeds grow, in a depth range of 0-30 meters
They reproduce by laying eggs in a loose, white ribbon of mucus, packed with many small eggs, which is then placed among weeds and algae.
Up to 4,5cm.
They feed on several species of siphonaceous green algae, especially Codium fragile and Codium stephensiae, but also feed on Ulva. They derive their body color from the actual algae they have been feeding on.
Elysia viridis is a remarkable species of slug since it can transfer chloroplasts (cells plants use for photosynthesis and thus energy) from the algae it eats into its own body and actively harness its energy, taken the best of both worlds, plant and animal.