Buried in sand all day with two folded flaps of solar panel on its back.
A sacoglossan to about 6 cm, olive to brown with a dense scatter of pale blue and black ocelli over the head and the two large parapodial flaps that fold over the back. Those flaps are opened and closed like a book, and the animal is often found half buried with only the folded flaps and the head showing above the sediment.
It is the most extreme of the solar-powered sea slugs. It pierces the cells of several species of green algae, retains the chloroplasts in its digestive tissue, and keeps them photosynthesising for weeks — which is why the flaps are opened flat in the light and why the animal can survive long periods with no food. The genes for maintaining a chloroplast are the alga’s, not the slug’s, and how the plastids last as long as they do is still argued over. Common on shallow sand and seagrass in some years and absent in others. Recorded from about 1 to 20 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
