A certain sea slug, known as Elysia chlorotica, can actually photosynthesize just like plants. Scientists discovered the slug off the east coast of North America from Nova Scotia to Florida and describe it as looking like a leaf itself. With the ability to photosynthesize, this slug can use energy from light to convert carbon dioxide into sugars. During this process, they also create oxygen. Again, this is just like plants. The slug is green in coloring and about 3 centimeters long.
The slugs gain the ability to photosynthesize by eating algae and incorporating the plant’s chloroplast, which contain chlorophyll, into their own cells. Cells in the slugs’ digestive tubules take the chloroplasts from the algae and keep them there for long periods of time. The slug never has to eat again.
It can complete its entire life cycle (about nine or ten months) by creating energy through photosynthesis. This includes reproducing. The slugs simply use the chloroplasts to keep creating chlorophyll and thus continue photosynthesizing.