Plant wannabes: Reef-building corals have algal symbionts that help them gain enough energy to build reefs. Certain sea slugs do it too - algal cells or chloroplasts are kept in the digestive glands of the sea slugs, which feed off carbohydrates or lipids produced by photosynthesis. In the latest issue of Science, Elizabeth Pennisi reports on recent recent studies have used molecular techniques to investigate this symbiosis.
Apparently algal cells or chloroplasts can for months in the sea slugs, and one species has acquired algal genes. According to Ingo Burghardt of Ruhr University in Bochum, Germany, the sea slug Phyllodesmium keeps zooxanthellae alive that it gets from the soft corals it eats A slug with algal symbionts can survive 260 days without food. The article also reports on the even more interesting case of Elysia chlorotica which acquires chloroplasts from the alga it feed on as a juvenile. Juveniles which don't acquire chloroplasts don't survive. (see article)