To endure the cold of deep waters, hammerhead sharks stop breathing

To endure the cold of deep waters, hammerhead sharks stop breathing

2023-05-28 06:15:06

Lidren learn it from an early age: you should not confuse a dolphin with a shark. One is rather nice and swimming alongside him is enchanting; the other is tougher and it is not recommended to spawn in its waters. One is a mammal, product of the evolution of a terrestrial creature returned to the sea, and breathes on the surface. The other is a fish, whose ancestors never left the liquid element, equipped with gills capable of filtering oxygen from the water. To fish, one dives while holding his breath. The other… Well the other too, at least some of them. In an article published on May 11 in the review Sciencea team from the University of Hawaii (United States) has just revealed that scalloped hammerhead sharks (Sphyrna lewini), one of the ten species of hammerhead sharks, simply stopped breathing during their stays in deep waters.

Read also: Article reserved for our subscribers Sharks fared better than other species in the face of the fifth great mass extinction

Every evening, these predators dive from 600 to 800 meters in order to catch their favorite prey: squid. At these depths, even in the tropics, the water temperature does not exceed 5°C. However, the shark is ectothermic. Unlike that of endothermic animals, commonly called “warm-blooded” – us humans, mammals, birds… – its temperature does not remain constant. Like reptiles in particular, it varies with the environment. “For an animal accustomed to tropical surface waters, such cold can be dangerousexplains Mark Royer, first signatory of the article. If the body cools too much, metabolism declines, including vision and nerve circuits, as well as muscles and the heart. »

To meet this challenge, certain so-called “high performance” fish, such as tunas, swordfish and white sharks, have biological particularities. Like a dynamo, part of their muscular energy is transformed into a source of heat. But nothing like this has been found in hammerhead sharks. How then does he manage not only to survive but to hunt in an ordinary way in such conditions? “We thought it could take advantage of thermal inertia, save heatcontinues the researcher. Upon discovering the data, we were stunned. »

The gills, “real natural radiators”

Mark Royer and his collaborators have equipped six fish with sensors capable of measuring both the depth and the temperature of the water, the internal temperature of the animal, its level of activity as well as the orientation of its body in the course of a dive. After a maximum of three weeks, the device detaches, rises to the surface and emits a VHF (“very high frequency”) signal. The researchers just have to fish it out and analyze the results. They then found that, during most of the maneuver, the animal maintains an almost constant temperature. It was only at the end of the exercise, more precisely towards the middle of the ascent phase, after about fifteen minutes in deep water, that the internal thermometer lost a few degrees… before quickly regaining them once at the surface.

You have 31.57% of this article left to read. The following is for subscribers only.

#endure #cold #deep #waters #hammerhead #sharks #stop #breathing


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Recent News

Editor's Pick