It is almost always completely dark in the ocean depths. But sometimes something also lights up as the sunlight is no longer enough. Bioluminescence is the name of the phenomenon when living things emit visible light through chemical reactions. It is known, among other things, from various deep-sea fish, but also from jellyfish, shrimp, and squid. Researchers outside New Zealand have now discovered that three shark species have also mastered the illumination trick, which was previously unknown.
In the specialized journal “Frontiers in Marine Sciences” A group led by Jerome Malevitt of the Catholic University of Leuven, Belgium, reported observations of Chatham altitude off the east coast of New Zealand in January 2020. They observed that black-colored sharks and southern lantern sharks could emit light. It has a bluish shimmer and can be seen mainly in the stomach area of animals.
“It is becoming increasingly clear that the production of light in depths must play an important role in structuring the largest ecosystem on our planet,” the researchers write in their report. Especially interesting: the chocolate shark has a body length of 1.8 meters, and it is also the largest vertebrate that can shine so far. The five-and-a-half meters long and very rarely basking mouth shark would also likely use bioluminescence. Indeed The researchers assumeThe glow here is caused by the captured plankton and the shark is only reflecting light.
The three species of sharks we are talking about now live in the mysterious world of the so-called Mesopelagic region, at depths of 200 to 1000 meters. An interesting question is what really brings animals their ability to shine here. A light belly may help them not to be seen easily from below because the contrast between the backlight and the light water surface is no longer too great. Or maybe it has to do with being able to search the ocean floor better in search of food.