The emerald green, leaf-shaped sea slug known as Elysia chlorotica can live for months at a time by
photosynthesizing its own food, like a plant does, but until recently scientists did not understand how the slug acquired and maintained this rare ability. A recent report in the journal The Biological Bulletin shows that the slug steals genes and chloroplasts — the cellular machinery that converts sunlight into food — from algae that the slug eats. Genes lifted from the algae can maintain cholorplasts in the slug for up to nine months, the researchers say — much longer than the chloroplasts would last in the algae themselves. Moreover, the slug can pass on those stolen genes to its offspring. The process is a mechanism of rapid evolution, says one of the study’s authors.