Solar Powered Sea Slugs Shed Light on Search For Perpetual Green Energy

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A mollusk, sea slug (Elysia chlorotica) which can grow to more than 2 inches long, is generally found in the intertidal zone between Nova Scotia, Canada, and Martha’s Vineyard, Massachusetts.

According to the study published in the journal Molecular Biology and Evolution, the juvenile sea slugs eat the brown alga (Vaucheria litorea) that is non-toxic and become photosynthetic or solar-powered. These slugs become self-solar powered due to the algal plastids which act like tiny solar panels and store them in their gut lining.

Photosynthesis is the process in plants and algae where sunlight is used to create chemical energy (sugars) from carbon dioxide and water. The plastids are the organelles in the brown algae which are filled with a green pigment called chlorophyll that converts light energy into chemical energy. This specific alga is an ideal food source as it does not have walls between adjoining cells in its body and is happened to be a long tube loaded with nuclei and plastids.

The sea slug makes a hole in the outer cell wall which helps to suck out the cell contents and gather all of the algal plastids at once. Some scientists have argued that other sea slugs steal and store plastids as food to be digested during hard times, like camels that store fat in their humps but this study has shown that it is not the case for solar-powered Elysia chlorotica.

The research team used RNA sequencing to check or test their solar energy supply hypothesis. The results show that sea slug responds in an active manner to the plastids by protecting them from digestion and turns on the animal genes to make use of the algal photosynthetic products. The scientists still do not know the actual function how sea slug maintains the plastids and photosynthesis for months without the nuclei. Further research is needed.

Senior author, Debashish Bhattacharya said, “It’s a remarkable feat because it’s highly unusual for an animal to behave like a plant and survive solely on photosynthesis” and further added “The broader implication is in the field of artificial photosynthesis. That is, if we can figure out how the slug maintains stolen, isolated plastids to fix carbon without the plant nucleus, then maybe we can also harness isolated plastids for eternity as green machines to create bioproducts or energy.”