Elysia chlorotica, common name the eastern emerald elysia, is a small-to-medium-sized species of green sea slug, a marine opisthobranch gastropod mollusc. Some members of this group use chloroplasts from the algae they eat; a phenomenon known as kleptoplasty. Elysia chlorotica is one of the "solar-powered sea slugs", utilizing solar energy via chloroplasts from its algal food. The incorporation of chloroplasts within the cells of Elysia chlorotica allow the slug to capture energy directly from light, as most plants do, through the process known as photosynthesis.
It’s easy being green for a sea slug that has stolen enough genes to become the first animal shown to make chlorophyll like a plant.
Shaped like a leaf itself, the slug Elysia chlorotica already has a reputation for kidnapping the photosynthesizing organelles and some genes from algae. Now it turns out that the slug has acquired enough stolen goods to make an entire plant chemical-making pathway work inside an animal body, says Sidney K. Pierce of the University of South Florida in Tampa.