Elysia
Elysia sea slugs eat algae. Some species such as E. viridis and E. chlorotica use the chloroplasts in the algae for themselves. The chloroplasts line the slug’s digestive tract. It lets the slugs live by photosynthesis for several months at a time. Exactly how the slugs use the chloroplasts is unclear. Many of the proteins used by chloroplasts are encoded in the genome of their cells. There are hunreds of these proteins. They are made in the cell’s nucleus. They are then moved into the chloroplast. This lets the slug.