Sea slug sustains self with photosynthesis

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This article was published 26/01/2010 (6062 days ago), so information in it may no longer be current.

A green sea slug that inhabits the saltwater marshes of Eastern Canada is being hailed as the first animal to feed itself using photosynthesis, the sunlight-derived energy source that sustains plants.

Research led by University of Florida biologist Sidney Pierce shows the emerald marine creature Elysia chlorotica — which shares North Atlantic coastal habitats with a species of algae called Vaucheria litorea — has evolved, over countless millennia, to absorb some of the plant’s photosynthesis-enabling genes into its own DNA.

The solar-powered mollusk, about three centimetres long, even looks like a small leaf. Early in life, each slug ingests key chlorophyll-producing cells from the algae in its environment. But the slug’s own built-in photosynthesis functions kick in after that, sustaining it for the rest of its life cycle of about one year.

"Those genes are already there, in the slug, and transferred from generation to generation," Pierce told Canwest News Service on Monday. While survival by photosynthesis is a defining trait in the plant kingdom, "that’s exactly what this slug does."

Noting that gene transfer between microscopic, unicellular organisms is known to occur, Pierce points out that "the most significant part of this is that genes have been transferred between two multicellular species. This is the first discovery of that happening."

Pierce outlined his research at a scientific conference earlier this month, and the detailed findings are to be published in an upcoming issue of the biology journal Symbiosis.

In 2007, the journal published a Pierce-led study that first indicated the possibility these sea slugs were surviving by photosynthesis. A study by another group of U.S. researchers, published in 2008 in the Proceedings of the National Academy of Sciences, bolstered the theory.

Now, said Pierce, his findings indicate the slug acquired "many, many" algae genes, so that the plant’s photosynthesizing structures have essentially been replicated within the animal’s own genetic code.

 

— Canwest News Service