Emerald Green Sea Slug Steals Genes from Algae to Photosynthesize Like a Plant

A brilliant-green sea slug can manage to live for months at a time without swallowing a morsel. Instead, it lives off of sunlight, like a plant. Now, scientists have figured out exactly how this sea slug managed the extraordinary feat; it turns out that it steals genes from algae.

The sea slug actually eats algae, and scientists suspected that the slug managed to develop its bright green color by snagging a few of the algae's genes. That's why the researchers used an advanced imaging technique to confirm that a gene from the alga V. litorea was present in the slug's chromosome. This gene actually creates an enzyme that is critical to the function of photosynthetic "machines," which are called chloroplasts.

The sea slug "steals" chloroplasts from the alga and then embeds them into its own digestive cells. Once inside the slug cells, the chloroplasts continue to photosynthesize for up to nine months, which is much longer than they would perform in the algae. This process creates carbohydrates and lipids, which nourish the slug.

Yet how exactly can the slug keep the chloroplasts working for so long? The researchers found that slug takes the gene responsible for repairing damage to chloroplasts and even transmits it to the next generation of slugs.

"There is no way on earth that genes from an alga should work inside an animal cell," said Sidney Pierce, one of the researchers, in a news release. "And yet here, they do. They allow the animal to rely on sunshine for its nutrition. So if something happens to their food source, they have a way of not starving to death until they find more algae to eat."

The findings reveal a bit more about this extraordinary adaptation that this sea slug employs. It allows it to survive for months without actually eating, relying on sunlight just like a plant.

The findings are published in the journal The Biological Bulletin.

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