There are about 550 species of shark in the oceans. Around twelve percent of them glow.

These luminous fish belong to two groups: the kitefin sharks and the lanternsharks. They are little creatures, no bigger than 50 centimeters long, and they feed on small fish, squid, and crustaceans. They also live in the deep ocean, which means that we know very little about how they live. But whatever they’re doing, they’re clearly doing it well. “They’re some of the most successful groups of sharks,” says Julien Claes from the Catholic University of Louvain. One genus alone—the Etmopterus lanternsharks—includes 38 distinct species. “And we discover new ones every couple of years.”

Claes has been studying these elusive fish for a decade, and has been