It's the ultimate form of solar power:

eat a plant, become photosynthetic. Now researchers have found how one animal does just that.

Elysia chlorotica is a lurid green sea slug, with a gelatinous leaf-shaped body, that lives along the Atlantic seaboard of the US.

What sets it apart from most other sea slugs is its ability to run on solar power.

Mary Rumpho of the University of Maine, is an expert on E. chlorotica and has now discovered how the sea slug gets this ability: it photosynthesises with genes "stolen" from the algae it eats.

Young E. chlorotica fed with algae for two weeks, could survive for the rest of their year-long lives without eating

They confirmed that if the sea slug used the algal chloroplasts alone, it would not have all the genes needed to photosynthesise.

attention to the sea slug's own DNA and found one of the vital algal genes was present.

Its sequence was identical to the algal version, indicating that the slug had probably stolen the gene from its food.