Sleeping sharks

Do sharks even sleep?


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Do sharks even sleep?

Annika from Leverkusen wants to know whether sharks are sleeping. What do the sea predators do to rest?

Sharks are impressive animals. There are more than 500 kinds of them. These predators elegantly master their element, the water. They come in a wide variety of sizes, from the lantern sharks, which are only around 20 centimeters long, to the great white sharks that are several meters long.

They belong to the cartilaginous fish and thus to the vertebrates. As the name suggests, they don't have bones, they have cartilage. This is supportive tissue that does not contain nerves or blood vessels. In the cartilaginous fish, a special type of lime accumulates there and gives the tissue strength.

Most sharks cannot or only briefly lie down on the ground and rest because of their breathing. Because they have gills to breathe, they are forced to swim constantly so that enough water flows over the gills so that their oxygen needs are met.

Ocean sharks are constantly swimming and resting. If they stood still, they would immediately suffocate. As they swim, they open their mouths. As a result, the water with the dissolved oxygen passes through the pharynx and through the gills. The oxygen is withdrawn and passed into the blood.

In order to have a little rest, these sharks stop all activities and swim calmly and slowly through the water, just like most other fish.

But there are many other species of shark that rest on the ocean floor, on a reef or in caves. For example, nurse sharks who like to hide under a rock alone to "sleep". Or they come together in whole groups when they lie on the seabed without protection. Other shark species also seek protection, for example under a ledge on the sea floor.

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