The slug Elysia chlorotica has the appearance of a leaf. Because it can photosynthesize like a plant, it can survive for weeks or even months without feeding. The chloroplasts come from the algae that the slugs consume.
The slugs Elysia chlorotica, which exist off the coast of the United States, not only eat algae; they also take up the chloroplasts from algae, which color their skin an emerald green. Algal genes have been integrated and are present in the DNA of these slugs, having been transferred from the nucleus of an algal cell to the nucleus of an animal cell.
Experiments have revealed that this sea slug, which resembles a little leaf about an inch or two in length, can live for nine months or more without feeding. They can survive by photosynthesizing the stolen algae parts under the sunlight.