Animals eat meat and plants to gain energy and nutrients, and plants use sunlight to gain energy through photosynthesis. Most people know that photosynthesis is strictly a plant characteristic, but what if there was an animal that could do photosynthesis to gain energy just like plants.
Prepare to be dazzled, because there is an animal that can do just that. A bright green sea slug, Elysia chlorotica, can live on sunlight just like a plant. This little sea slug is about an inch long, lives in salt marshes in the eastern United States, and feeds on algae. It has been called the photosynthesizing sea slug in the past because of its unique ability. So how is this animal able to gain nutrients through a process that seems to be exclusive to the plant kingdom? Studies have shown that this little sea slug is able to incorporate genes from the algae that it consumes.
Plant photosynthesis is accomplished in plant cells through chloroplasts. Chloroplasts contain chlorophyll, which is the green pigment seen in the plant cells, and is used to convert light energy into sugars.
When the sea slug eats the algae Vaucheria litorea it sucks out the chloroplasts from the cells. As the chloroplasts pass through the sea slug’s digestive system it embeds the chloroplasts into their own digestive cells where they continue to photosynthesize for as much as a year. Sidney Pierce from the University of South Florida has researched exactly how these sea slugs are able to accomplish this. Through his research, he has discovered that the sea slugs contain proteins in their cells which are able to maintain the chloroplasts and enable them to continue to photosynthesize. What this means is that these sea slugs can exist, including growth and reproduction, without eating for up to a year.
The genes which enable the sea slug to maintain the incorporated chloroplasts pass on to future generations, this means that all the baby sea slugs need to do is eat some algae to get some of their own chloroplasts and it will also be able photosynthesize like its parents. This is an amazing phenomenon, but this ability only allows the sea slug to survive and is used more as a reserve rather than a primary source of nutrition and the sea slug will eventually die if it cannot continue to feed on algae.