The sea slug, which looks rather like an oak leaf, is a very unique animal; one of a kind in fact, as Texas A&M biologists have discovered. These slugs actually behave like plants, using photosynthesis to capture solar energy and convert it into food.
How do they do this? Sea slugs feed on a specific type of algae which, as a plant, works like a solar powered machine. The alga contain organelles, called plastids, that trap sunlight and convert it to energy. The sea slug then feeds on the alga by cutting it and sucking out the cytoplasm, digesting most of it. In an interesting twist, however, the slug retains some of those plastids which continue to trap sunlight inside the slug and create food.
Such a trait has never been found in animals, which normally rely solely on plants and other animals for nourishment. Researchers note that the sea slug, with a full belly, can use these plastids for food to survive at least nine months without consuming anything else.
The slug is dependent on the alga to live out its life. How it does this is still somewhat a mystery to scientists but there is no longer any doubt that stealing the alga’s plastids is exactly what it does. The researchers know that the slug contains at least one gene necessary to survive using photosynthesis, and probably more. New slugs are not born with the ability, however, and need to collect their own algae to grow themselves. But the slug could evolve to into a truly photosynthetic animal (i.e., born with plastids) somewhere down the evolutionary line, providing both the slug and alga survive changing climatic conditions.
Scientists will now work to map the sea slug’s genome in an effort to explore deeper this unique creature’s very unique abilities. Learning how an animal, even a slug, can live like a plant has some amazing implications for solar energy research in general.