Solar-powered sea-slugs live like plants,...( COLLEGE STATION Nov. 25 2008 The lo...)

COLLEGE STATION, Nov. 25, 2008 The lowly sea slug, "Elysia chlorotica," may not seem like the most exciting of creatures, but don't be fooled: it behaves like a plant and is solar-powered, says a Texas A&M University biologist who has been studying these tiny creatures for the past decade and, along with collaborators from several universities, has identified a possible cause of their ability to behave like plants.

Biology professor James Manhart is a member of a research group that believes they have identified some of the secrets of the sea slug and its curious plant-like behavior. These research findings have been published in the current issue of "Proceedings of National Academy of Sciences" with an image of a green slug gracing the cover.

Manhart says plants can be compared to solar-powered machinestheir cells contain tiny organelles called plastids that trap sunlight and convert it into energy by a process known as photosynthesis. Animals, on the other hand, depend on plants or other animals for their energy needs.

The sea slug, however, works a little differently. Its main food source is a specific type of alga. "It makes a cut in the alga, sucks out the cytoplasm [the material inside the alga] and digests most of it," explains Manhart.

But there's a twistit retains the plastids that trap the solar energy.

These plastids remain in the slug, continue to photosynthesize and provide food for the slug. In effect, the creature becomes a solar-powered slug and is able to make its own food like plants do.

"Photosynthesis needs around 2,000 to 3,000 genes, and animals do not have many of the critical genes," says Manhart. So Manhart and his co-workers looked into how the plastids consumed by the slug can continue photosynthesizing.

"We found that the slug has at least one gene required for photosynthesis in its nuclear genome, which has never been found in any animal," says Manhart. "The critical thing is the plastids come f
'/>"/>