Scientists say they have discovered that three species of deepwater shark glow in the dark, including the largest known luminous vertebrae.
The researchers studied sharks from waters off the coast of New Zealand in the first experimental study of its kind.
The kitefin shark, blackbelly lanternshark and southern lanternshark were already known to marine biologists, but have now been found to be bioluminescent, or able to emit light.
The kitefin, which the researcher refers to as a “giant luminous shark”, is the largest-known glow-in-the-dark shark.
Other sea life, including jellyfish and squid, are known to emit light.
The scientists, from Université Catholique de Louvain in Belgium and New Zealand's National Institute of Water and Atmospheric Research, said that the shark species might emit light in an attempt to hide from predators.The sharks live in the "mesopelagic zone", which ranges from 200 to 1000 metres deep. As sunlight cannot reach this area, sea life appears backlit to predators positioned below.
The kitefin has few or no predators - the scientists believe emitting light may help it to see food or disguise itself when approaching prey.
In the Frontiers in Marine Science journal, the researchers said further study is needed to confirm these theories.