The sea floor is one of the most remarkable and least studied ecosystems on the planet. At the top, at a depth of between 200 and 1000 meters, there is a region of medium seas or twilights, where only a small amount of sunlight arrives. This is the home where the three species of sharks that are able to emit light in the dark have been discovered. A team of scientists from the Catholic University of Leuven (Belgium) traveled to New Zealand in January 2020 and spent a month on the high seas studying sharks at Chatham Rays, on the country’s east coast. Jerome Malefitt, Expedition Leader, has devoted his entire life to studying these fish and is convinced that 11% of known shark species are bioluminescent. His trip to New Zealand allowed him to prove this to the scientific community with three of these species, in a study published in the journal. Frontiers in Marine Sciences.
Mallefet has managed to capture samples from three different families: the Ventral Black Lantern Shark (Etmobarus of LuciferSouthern Lantern Shark (Etmopterus granular(The kite shark or karuchu shark)Dalatias though). He transported them to a water tank in a darkened room on the ship, where his team was able to photograph the animals that emit a stunning blue-green light. “It was my dream to see Dalatias though It shines because no one in the world has seen it before, and I am convinced that it is the largest bioluminescent shark known to date, ”explains Mallefet, referring to the carocho shark, which can reach a length of 180 cm and became thanks to this discovery, in the largest luminous vertebrate in the world.
Bioluminescent animals have organs, photoreceptors, and they are the ones that produce light. In most of them this process is controlled by the nervous system. But when the Belgian team of scientists studied flogging Sharks Captured, where the photosynthetic images were found, he was surprised to discover that they are the only animals whose production of light is controlled by hormones. “It took us an entire year to figure out how the light organ was stimulated by the failure of all the neurotransmitters,” says Malift. Until they realized that melatonin, the same hormone that stimulates sleep in humans, is the photostimulant in sharks: “Melatonin stimulates light production and alpha-MSH stops it. It’s a very slow process.”
The light these sharks give off helps mask their shadow and not alert other predators to their presence.
The researchers’ next step was to find out why the sharks emit light. Mallefet believes the most plausible hypothesis is that it is a camouflage technique to survive in an area Ocean As there are not many places to hide: “A small shark like this can be eaten by any large fish or other shark. If it is swimming and there is a blue light above it, then when a predator passes underneath it, the shadow of its prey can easily be seen contrasting with The light. But if the shark silhouette also produces blue light, the two light will mix. It is called the counter shadow hypothesis, which is to shine so that it disappears and avoid being eaten by predators.
An expedition of the Belgian team has been conducted in New Zealand waters thanks to NIWA, the country’s National Institute of Marine and Atmospheric Research. Darren Stevens He is an expert fishing scientist who was in charge of the ship. In his career, he caught many unusual fish (including two giant squid) but he never expected that the sharks he saw constantly could glow in the dark. “We have seen bacteria and algae that emit light, as well as squid that releases bio-ink, and we have caught many small fish that live in the twilight region that have the same quality, such as the lantern fish that also have photosynthesis, and of course a fish. It has an antenna that protrudes from it. Its head can be lit to attract prey into its mouths … Yes, I have seen many fish glow, but I never imagined that some great shark could do the same if you think of the stone shark, which is 1.8 meters long and weighs up to 30 kilograms They are large and impressive animals, and to discover that they can communicate via bioluminescence is unbelievable. “
Stevens agrees with Belgian researcher Jerome Mallefet to discover these Sharks It can help understand the role of bioluminescence on the sea floor. In the animal kingdom, 80% of bioluminescence is found in the oceans and the only vertebrates that can produce light are those that live in salt water. “5% of the oceans are the sea surface and the remaining 95% make up the sea floor, and it is the largest habitat in the world and we know almost nothing about it,” Malefit says with a broad smile, hoping he can participate. On another cruise once the pandemic is under control. His dream is to continue investigating the dark areas of the ocean and see if bioluminescence, he believes, is a form of communication for inhabitants of the depths.