Is it true that sharks are never sleeping?

It is widely believed that sharks are unfamiliar to sleep, because for the work of gills they need to constantly remain in motion. We decided to check what scientists know about the rest of these fish.

That sharks are never sleeping, write as ordinary InternetUsers, and large media. For example, RIA Novosti claims: “Sharks do not sleep at all. They are in motion from the first to the last second of life. ” “Teacher's newspaper” in the article “The whole thing is ..., or why the birds do not fall, and the fish do not drown-the top 10 children's“ why ”” tellsthat sharks "have to move without sleep and rest, so as not to get" water "in the mouth and not suffocate." And the magazine "Around the World" reportsthat "sharks generally need to be in motion all the time, since their relatively imperfect gills should constantly be washed with water." Questions “Why are sharks not sleeping” and “Why sharks never stop” Interested users different sites questions And answers.

Sharks, along with slopes, are a yield of cartilaginous fish. Scientists know more than 500 species of sharks - from the deep -sea small etmopterus perryi from the genus of black prickly sharks, size which only 16 cm, to a whale shark, achieving in length 19 m. sharks existed Another 400 million years ago. Most known species live in sea salty water, but there are those that are found in freshwater reservoirs. 

Like other fish, sharks breathe, extracting oxygen from the water that they pass through the gills. Outside in front of the chest fins located from five to seven gill slots, and inside, in the walls of the pharynx, are the ranks of gill petals that are on the gill arches. For a long time it was believed that due to the weak jaw muscles, sharks can only be used by passive or running, ventilation of gills-water enters the body when the animal moves. Accordingly, if the fish stopped on the spot, including in order to take a nap, it would have to suffocate. 

However, not everything is so tragic. At the coast of the Yukatan Peninsula there is a whole cave called a cave of sleeping sharks. This is a unique place discovered In 1969, local fisherman Carlos Garcia Castilla. He noticed that sharks swim in this cave and remain inside for a long time. He told Ramon Bravo, ecologist and diver about his observation. Subbed into the cave, they found a stupid shark, also known as a shark-bic, which lay motionless at the bottom and made the impression of sleeping. 

Bravo managed to photograph this unique phenomenon and provided pictures of scientists specializing in the study of sharks, - shelton Applegate and Eugene Clark, famous Under the nickname Lady Shark. The world scientific community became interested in an unusual location, and in 1970, Ramon Bravo became a guide for a cave for the famous French researcher Ocean Jacques-Iva Kousto.

Scientists They thinkthat due to the influx of fresh water from land in this place, the water is less salty, and underwater sources from the bottom of the cave saturate it with small oxygen bubbles, which can have a sleeping pills. Also system of underwater channels does water current is more active, and sharks can Relax in immobility. However, divers note that some fish look at people, so they cannot be considered sleeping. At least, a cave of sleeping sharks precisely demonstrated that sharks could remain in one place for a long time and not die from choke.

Shark scientific evidence of Shark was discovered only recently. A group of scientists from the University of Western Australia under the leadership of the ecophysiologist Michael Kelly studied different types of endemic sharks to the region, who were placed in special aquariums that imitate the environment familiar to them. In 2020, researchers Shared The first conclusions. In certain periods, the Australian bull and New Zealand cat -headed (aka checker) species were required to react to the stimulus than to others. Since one of the signs of sleep in animals is an increased threshold of excitation, this observation gave scientists the opportunity to declare that animals sleep in such periods. 

In 2022, the same team of scientists Shared Another important discovery - during the rest of the sharks, the level of metabolism decreases, which is also refers To the signs of sleep. At this time, sharks also consumed less oxygen - this is consistent with the fact that breathing in a dream slows down in all animals, including man. At the same time, the sharks closed their eyes during the rest of the rest - in bright light imitating daytime, almost all individuals preferred to sleep with their eyes closed, but “at night” 38% of the fish held their eyes open, although all other indicators testified that the animals were sleeping. “Closing the eyes is most likely associated with an external factor, such as the presence of light, and not with sleep,” - suggest scientists. Thus, the discoveries of Kelly and the teams completely refute the belief that no types of sharks can sleep.

Different species of these animals during evolution have developed their ways to adapt the body to rest and oxygen pumping. For example, in katrans, or thorny sharks, nerves that provide coordination of movements during swimming, are located Not in the brain, but in the spinal cord, which allows fish and swim (therefore, breathe) and sleep at the same time. There is also hypothesisthat some types of sharks can simultaneously swim and sleep, turning off only one hemisphere of the brain. In the same way, for example, Sleep Dolphins and sea seals when they are in the water. 

Thus, the belief that the sharks of nature are doomed to insomnia and the eternal movement are nothing more than a myth. Scientists observed both motionless sharks, which breathed due to the special flow of water, and sharks, which showed us the usual signs of sleep - an increased threshold of excitability, a more rare breathing and slow metabolism. Evolutionarily nature provided for various mechanisms to give this type of fish to relax.

Image on the cover: Image by Andrea Bohl from Pixabay

Not true

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