Between 200 and a thousand meters deep, in the waters off the east coast of New Zealand, there are three species of sharks that shine with their own light. This was discovered by researchers from the Université Catholique de Louvain in Belgium and the National Institute of Water and Atmospheric Research in New Zealand, who thus become the first to document the phenomenon of bioluminescence in such large vertebrates, up to 180 cm.
How sharks communicate: they light up in the depths
Bioluminescence. The sea depths aren’t as dark as you might think. We have known this for some time: just as on land there are organisms capable of emitting light (fireflies, for example), even in deep waters there are animals (squid, molluscs, and even a dozen species of sharks) with the same capacity. . The phenomenon is known as bioluminescence, and scientists think it has several purposes, such as attracting prey or, conversely, escaping predators.
The largest bioluminescent vertebrate. The study conducted by Jérôme Mallefet and his colleagues, however, for the first time documents the phenomenon of bioluminescence in medium-large vertebrates: Dalatias licha, Etmopterus lucifer, and Etmopterus granulosus. D.licha (or shagreen shark), in particular, with its 180 cm in length, thus becomes the largest bioluminescent vertebrate discovered so far.
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by SANDRO IANNACCONE
The team of scientists spent a month at sea recovering some shark specimens in deep water to observe them, alive, in a tank of seawater in dark conditions. The researchers’ eyes lit up as the animals began to radiate blue-green light.
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Light in the depths. To shine, marine biologists describe in the article published in Frontiers in Marine Science, is above all the abdomen, where specialized cells (photocites) responsible for bioluminescence have been found. The mechanism, however, is not yet clear: it is only known that these sharks activate photocites through melatonin, a hormone involved in the regulation of circadian rhythms also in humans.
For experts, the discovery, while not so unexpected, is exciting: it not only reinforces the idea that light is an advantage even in the darkest places, but at the same time it reflects how little we still know about the largest ecosystem on the planet.
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