The biofluorescent shark Scyliorhinus retifer. (Credit: David Gruber)

(Inside Science) — When we look at the seafloor, we might not see the bottom-dwelling sharks that blend in with the rocks and the sand. But to other sharks of the same species, they stand out like green glow sticks. Now scientists know how.

In 2014, marine biologist David Gruber, from the City University of New York, and his team discovered that two species of bottom-dwelling sharks are biofluorescent. The swell shark