It’s the largest bioluminescent creature ever found
Researchers working off the east coast of New Zealand have discovered three species of deep-sea sharks that glow in the dark. The kitefin shark, the blackbelly lantern shark, and the southern lantern shark had not previously been known for bioluminescence. All have specialized cells that produce a blue-green light as they prowl the deep sea.
The kitefin shark grows up to 180cm, which makes it the largest-known luminous vertebrate in the world. “I nearly cried when I saw it, it was so exciting,” said Jérôme Mallefet of the Catholic University of Louvain, in Belgium, who has spent his career studying marine bioluminescence. Previously, only a dozen shark species were known to glow like this.
These new finds show how common bioluminescence is in marine wildlife. The trait has evolved independently dozens of times and occurs in everything from fireflies to those single-celled organisms on the surface of the ocean that glow when disturbed.
During the project, researchers plucked the sharks from the ocean’s twilight zone at a depth of approximately 800m. They then transferred the animals to tanks in dark rooms so that their luminosity could be observed and photographed.
Later, researchers autopsied the sharks to study their glow-in-the-dark organs. It should be noted that none of the species are classed as vulnerable.
Less is known about the deep sea than any other environment on earth, but it is thought that three-quarters of creatures found there could be bioluminescent. , being able to create light for hunting or mating would be a huge asset.
“It is…obvious that producing light at depth must play an important role in structuring the biggest ecosystem on our planet,” the researchers wrote in their study.
Mallefet describes lantern sharks as MacGyvers of light because they use their light in so many ways. According to one theory, the blue-green luminous organs on their undersides help them blend in with the pale light above, camouflaging them from predators below. Lighting the seafloor may also help them find food and attract a mate.
The kitefin shark’s glowstick qualities are much more puzzling. It has no known predators, so nothing to deter. And its dorsal fin specifically glows. “Why? For which purpose?” wonders Jérôme Mallefet.
Mallefet’s earlier research has shown that unlike other bioluminescent creatures, the hormone melatonin regulates the light produced in sharks. “It makes us fall asleep, but it’s lighting up the shark,” he says. He and his fellow researchers are trying to find the on-off switch that controls these hormones.
“A lot of people know that sharks can bite, thanks to Jaws,” Mallefet told National Geographic. “but few people know that they can glow in the dark.”