Meet the Solar-Powered Sea Slug that Performs “Animal Photosynthesis”

Photosynthesis is the process by which plants produce their own energy from sunlight, water, and carbon dioxide. This essential process occurs in a specialized compartment of plant cells called the chloroplast, where a green pigment called chlorophyll is used to absorb sunlight. Some animals have figured out how to hijack this system by eating plants and using their chloroplasts to make energy, including some sea slugs. These fascinating solar-powered animals were recently the focus of a study by a group at Harvard University. 

The authors wanted to know how these slugs maintain functioning chloroplasts without the rest of the plant cells around to support them. They found that the slugs regulate specialized compartments to maintain the proper conditions for chloroplast survival and function, adjusting factors like salt concentration. Since the slugs take organelles from plants, the authors cleverly coined this compartment the “kleptosome” after the Greek root meaning “to steal”. Another finding from this study relates to the fate of the kleptosome once sunlight is not available. When the chloroplasts can no longer produce energy, the slugs digest them to use for extra energy, enabling months of survival without sunlight or other food sources. The slugs then appear with a yellow color, a phenomenon akin to the leaves changing color in the autumn due to loss of chlorophyll. 

This research is remarkable for both its findings and its methods, since studying biological processes in an organism as small as a sea slug presents many challenges that the authors overcame. Importantly, this type of research, which studies the clever ways in which organisms have adapted to produce energy, lead to a deeper understanding of evolutionary biology. 

This study was led by Corey Allard with corresponding authors Amy Lee and Nicholas Bellono at Harvard University/Harvard Medical School/Dana Farber Cancer Institute.

Managing Correspondent: Olivia Lavidor

Press Article: ‘Wildest thing’: solar-powered slug steals chloroplasts and stores them for emergencies (Nature Briefing) 

Original Journal Articles: A host organelle integrates stolen chloroplasts for animal photosynthesis (Cell)

Image Credit: Vierschilling/pixabay