This slug chops off its own head, and more curiosities

Sea slugs are regenerating new bodies, sharks are glowing in the dark, and seedlings are in short supply.

Scientists in Japan have discovered that two species of sea slugs can rip off their heads and regenerate new bodies, organs and all, in less than a month. Scientists theorize that the slugs, Elysia marginata and Elysia atroviridis, do this to rid themselves of internal parasites.  —Annie Roth

Scientists studying deep-sea life off the New Zealand coast identified three species of sharks that are bioluminescent—that is, they glow in the dark. These species—the blackbelly lanternshark, southern lanternshark, and kitefin shark (below)—produce a soft blue-green light using specialized cells in their skin. The kitefin shark, at nearly six feet long, is one of Earth’s largest animals capable of emitting light. 

The find is a reminder of “how much we still have to discover and understand about the deep ocean and its inhabitants,” says biologist Diva Amon, a National Geographic emerging explorer. More research is needed on how common bioluminescence is among deep-sea sharks, and how they employ it. Scientists suspect that the sharks, by making their bellies glow, can hide their silhouette from predators lurking in deeper, darker waters—a trick known as counterillumination.  —AR

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