Meet The Solar-Powered Sea Slug That's Half Animal, Half Plant

Meet The Solar-Powered Sea Slug That's Half Animal, Half Plant

When we think of animals and plants, we have a pretty good way of dividing them into two distinct groups: one converts sunlight into energy and the other has to eat food to make its energy. Well, those dividing lines come crashing down with the discovery of a sea slug that is truly half animal and half plant. It's official name is Elysia chlorotica and it's pretty incredible how it has managed to hijack the genes of the algae on which it feeds.

The slugs can manufacture chlorophyll, the green pigment in plants that captures energy from sunlight and hold these genes within its body. The term kleptoplasty (retention of “stolen plastids”) is used to describe the practice of using hijacked genes to create nutrients from sunlight. And so far, this green sea slug is the only known animal that can be truly considered solar-powered, although pea aphids and spotted salamanders exhibit some plant-like behaviors. Many scientists have studied the green sea slugs to confirm that they are actually able to create energy from sunlight.

According to NBC News,

"In fact, the slugs incorporate the genetic material so well, they pass it on to further generations of slugs. The babies of thieving slugs retain the ability to produce their own chlorophyll, though they can't carry out photosynthesis until they've eaten enough algae to steal the necessary chloroplasts, which they can't yet produce on their own." -NBC News

Karen Pelletreau's study shows close-up photos of the sea slug's skin. Figure A's explanation goes as follows:

"Fig.A: The digestive system consists of densely packed tubules that branch throughout the animal's body. Each tubule is made up of a layer of single cells containing animal organelles and numerous algal plastids." -Karen N. Pelletreau et al.

Anatomy of the sacoglossan mollusc Elysia chlorotica.(A) Sea slug consuming its obligate algal food Vaucheria litorea. Small, punctate green circles are the plastids located within the extensive digestive diverticula of the animal. (B) A defined tubule of the digestive diverticula extending into the parapodial region of the animal (arrow). The digestive system consists of densely packed tubules that branch throughout the animal's body. Each tubule is made up of a layer of single cells containing animal organelles and numerous algal plastids. This cell layer surrounds the lumen. (C) Magnified image of the epidermis of E. chlorotica showing densely packed plastids. The animals are light grey in color without their resident plastids, which contribute chlorophyll to render the sea slugs bright green.[Image Source: Wikimedia Karen N. Pelletreau et al.]

From the IFL Science website,

"There is no way on earth that genes from an alga should work inside an animal cell," says Sidney Pierce from the University of South Florida. "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." -IFL Science

The sea slugs are so good at photosynthesis that they can live up to 9 months without having to eat any food. They get all their nutritional needs met by the chloroplasts that they've hijacked from the algae.

Anatomy of the sacoglossan mollusc Elysia chlorotica.(A) Sea slug consuming its obligate algal food Vaucheria litorea. Small, punctate green circles are the plastids located within the extensive digestive diverticula of the animal. (B) A defined tubule of the digestive diverticula extending into the parapodial region of the animal (arrow). The digestive system consists of densely packed tubules that branch throughout the animal's body. Each tubule is made up of a layer of single cells containing animal organelles and numerous algal plastids. This cell layer surrounds the lumen. (C) Magnified image of the epidermis of E. chlorotica showing densely packed plastids. The animals are light grey in color without their resident plastids, which contribute chlorophyll to render the sea slugs bright green.[Image Source: Wikimedia Karen N. Pelletreau et al.]

Leah Stephens writes under the pseudonym, Stellabelle. She is an artist/researcher who writes books and you can connect with her here. 

SEE ALSO: Geothermal Power Plant Turns CO2 Emissions Into Solids

Written by Leah Stephens

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