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Scientists studying sharks off New Zealand’s coast have discovered that three species of the high seas glow in the dark – one of which is now the largest luminous vertebrate known.
Bioluminescence – the production of visible light by chemical reaction by living organisms – is a widespread phenomenon in marine life, but this is the first time it has been documented and analyzed in the kite shark, the lantern shark black bellied and southern lantern shark.
The sharks were caught during a fish survey from Chatham Rise off the east coast of New Zealand in January 2020.
The kitefin, which can grow up to 180cm, is now the largest known luminous vertebrate: what researchers have called a “giant luminous shark”.
The researchers, from the Catholic University of Louvain in Belgium and the National Institute for Water and Atmosphere Research in New Zealand, said the findings had implications for our understanding of life on the high seas. ; one of the least studied ecosystems on the planet.
Sharks all live in what is known as the mesopelagic or “twilight” zone of the ocean, between 200 and 1000 meters deep, beyond which sunlight does not penetrate. Seen from below, sharks appear backlit against the shiny surface of the water, leaving them exposed to potential predators with no place to hide.
Researchers suggest that the glowing bellies of these three species can help them camouflage themselves from any threats that might strike from below.
In the case of the kite shark, which has few or no predators, it is possible that the slowly evolving species uses its natural glow to illuminate the ocean floor as it searches for food, or to disguise themselves by approaching their prey.
Further study would be needed to confirm either hypothesis, the researchers wrote in an article published in the journal Frontiers in Marine Science, as well as to understand how the species’ bioluminescence works – and the implications. possible for prey-predation relationships.
“Given the immensity of the deep sea and the presence of luminous organisms in this area, it is increasingly evident that the production of light at depth must play an important role in the structuring of the larger ecosystem of our planet, ”the researchers write.
Jérôme Mallefet, principal researcher at the marine biology laboratory of the Catholic University of Louvain in Belgium, said: “The light pattern of the kitefin shark was unknown and we are still very surprised by the glow on the dorsal fin. Why? What purpose? “
The size of the territories inhabited by sharks makes this type of study very difficult, he said. “The other two Etmopterus sharks have not been documented either, so this is the first time.”
Mallefet hopes to be back at sea soon to continue the work, and look for brighter species.
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