According to biologists who have been studying the Elysia Chlorotica for more than two decades, the bright green ocean dweller is both an animal and a plant. It appears as if this slug has consumed so much algae overtime that it has evolved the ability to convert sunlight into energy, like plants do by photosynthesis.
Sidney Pierce, a biologist from University of South Florida explained that these sea slugs, which can be found in salt marshes of New England and Canada, carry out photosynthesis by using chlorophyll-producing genes and cell parts called chloroplasts from the algae they consume. This genetic material has been passed down to the next generation in line, to the point that the sea slugs no longer need to consume algae for energy.
Pierce's research team collected the species and kept them in aquariums for months. As long as they were exposed to sun for 12 hours per day, the sea slugs could survive without food. However, the baby slugs could not carry out photosynthesis until they stole their own stash of chloroplasts from their first and only meal of algae.