Conservation news

Scientists discover three glow-in-the-dark sharks

Luminescent patterns of Dalatias licha. Photo by Jérôme Mallefet / UC Louvain.

  • Researchers have discovered that three deep-sea shark species — the kitefin shark (Dalatias licha), the blackbelly lanternshark (Etmopterus lucifer), and the southern lanternshark (Etmopterus granulosus) — all have bioluminescent properties.
  • The kitefin shark, which glows blue, is the largest known vertebrate to emit bioluminescence.
  • Further research is needed to fully understand how and why these sharks emit light.

The kitefin shark is a guitar-sized creature with brownish-black skin and large, gaping eyes. But there is more to this shark than initially meets the eye: in the dark, it will emit a blue glow.

On a 2020 voyage near Chatham Rise off the eastern coast of New Zealand, a team of international scientists discovered that the kitefin shark (Dalatias licha) and two other deep-sea shark species, the blackbelly lanternshark (Etmopterus lucifer) and the southern lanternshark (Etmopterus granulosus), all have bioluminescent properties.

“We have something like 540 shark species in the ocean [and] there are 57 of them able to produce light — so more than 10% of the sharks,” Jérôme Mallefet, a marine biologist at the Catholic University of Louvain in Belgium and lead author of a new study on the discovery, told Mongabay in an interview. “But do people know they are able to produce light? No, not much.”

Luminescent patterns of Dalatias licha. Photo by Jérôme Mallefet / UC Louvain.

There are countless other species that are bioluminescent — from jellyfish to squid to algae — but the kitefin shark is the largest known vertebrate to produce bioluminescence, according to the study.

The three shark species inhabit the mesopelagic zone of the ocean, also known as the twilight zone, which ranges from 200 to 1000 meters (660 to 3,300 feet) in depth. Only the tiniest amount of sunlight can reach this region, creating a dim, blue glow.

Most marine organisms that produce bioluminescence contain special chemicals, including a compound called luciferin that interacts with oxygen to produce light. But these three sharks do not appear to contain the same chemical properties, so their ability to emit light “remains enigmatic,” the researchers say.

“For the moment … our conclusion is that, maybe sharks have a new component that is unknown,” Mallefet said. “But we don’t know.”

While there is still a lot to be learned about these deep-sea sharks, the researchers suggest the ability to emit bioluminescence could be used to find food, attract mates, or camouflage themselves in the faint blue light of their environment.

Lateral luminescent pattern of Dalatias licha. Photo by Jérôme Mallefet / UC Louvain.

“I tend to say they are the MacGyver users of light, because they use bioluminescence in many different ways,” Mallefet said.

He said he hopes to continue his work on bioluminescent sharks, as well as other species, as soon as he is able to safely travel again.

“Many people say the deep sea is less known than the surface of the moon,” he said. “We hope by highlighting something new in the deep sea of New Zealand — glowing sharks — that maybe people will start thinking we should protect this environment before destroying it.

“I hope the new generation will carry that message,” he added. “And I’m more than happy to [add] my little piece of the jigsaw to a big program to protect the ocean.”

Citation:

Mallefet, J., Stevens, D. W., & Duchatelet, L. (2021). Bioluminescence of the largest luminous vertebrate, the kitefin shark, Dalatias licha: First insights and comparative aspects. Frontiers in Marine Science, 8. doi:10.3389/fmars.2021.633582

Elizabeth Claire Alberts is a staff writer for Mongabay. Follow her on Twitter @ECAlberts.

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