Bioluminescence refers to the production of visible light by living organisms through a biochemical reaction. It is suspected that about 57 of the 540 known shark species may produce light, co-author Jérôme Mallefet, head of the laboratory for marine biology at UCLouvain, told CNN on Wednesday.
While samples have previously shown that the kitefin shark would be able to produce light, it is ‘very difficult to observe’ as they are between 200 and 900 meters (656-2,953 feet) below the surface of the ocean. live, Mallefet said.
Bioluminescence has also been documented in two other species of deep-water shark, Etmopterus lucifer (the black-bellied lantern shark) and Etmopterus granulosus (southern lantern shark), as part of the research.
Mallefet noted that the sharks were caught by accident during NIWA’s trawling surveys, which are used to measure fish stocks, the organization contacted.
He was invited to take part in a survey voyage in January 2020 and spent 30 days on board the boat and caught several sharks.
“I was just like a child at the bottom of a Christmas tree,” Mallefet said, describing how he managed to catch a kite fin shark in a bucket in a dark room on the ship.
The deep sea below 200 meters (656 feet) is described as the twilight zone. Many people mistakenly believe that no light is visible, but there is light that the sharks find useful, Mallefet said.
“They use light to disappear,” he said, explaining how bioluminescence can make sharks invisible against the light glow of the ocean’s surface.
It protects the sharks from predators swimming beneath them, and also makes it easier for them to hunt prey, Mallefet said.
“We know this is the case with Dalatias licha,” he said, while the remains of smaller sharks were found inside the belly of some monsters, despite the fact that the species is the slowest swimming shark in the world.
However, the glowing sharks did not give up all their secrets, nor why their dorsal fin glows.
Further research is needed to find out if it can be used for signaling, Mallefet said, adding: “There are still question marks.”
Mallefet told CNN he wants to study the dorsal fin in more detail about future trips to the area, as well as to see what the sharks eat and whether they are eaten.
The goal is to learn more about the deep sea, which remains mysterious, despite being the most common environment on earth, to make people think more about its conservation, he said.
“I’m afraid we made a lot of mistakes in throwing things into the sea,” Mallefet said. “I fear what will happen to future generations.”