What sharks have spiracles

Do sharks never sleep?

Spiny dogfish


Florida Museum of Natural History:

It was once believed that all sharks had to swim constantly to breathe and couldn't sleep for more than a few minutes at a time. During movement, oxygen-rich water flows through the gills so that the shark can breathe.

While some species of shark have to swim constantly, not all sharks do .

Some sharks like the nurse shark have spiracles that push water over their gills and thus enable stationary rest .

Sharks don't sleep like humans but have active and restful times .



ReefQuest Center for Shark Research :

... when it comes to whether or not sharks sleep, we just don't know .

There have been reports from all over the world including Mexico, Japan, and Australia of sharks resting motionless in caves. These have been called "sleeping sharks," but I can confirm that the eyes of these dormant sharks follow divers who move around the caves with them, so they definitely don't sleep.

From experiments with a small shark named Spiny Dogfish ( Squalus acanthias ) we know that the "Central Pattern Generator", which coordinates the swimming movements of sharks, is not located in the brain, but in the spinal cord.This is how an unconscious shark can swim.

There's even a chance the sharks' forebrain, mid-, and hindbrain will shut down one at a time, resulting in a shark equivalent of sleepwalking .



NEWTON - Ask a scientist :

... we don't know whether sharks sleep or not .

Many species of shark need to swim constantly to breathe (or breathe), but that doesn't necessarily mean they aren't "sleeping".

Many animals can turn off part of their brain for a short period of time while other parts remain "awake" or vigilant looking for predators.

Other animals slow their brain function only for a certain amount of time each day;

Sharks can do these things too although they continue to swim. It is also possible that they will not sleep at all.

The only way for us to find out for sure is to catch them and constantly measure their brain activity.



Indianapolis Zoo :

It is unclear how sharks sleep.

Some sharks may lie on the bottom while actively pumping water down their gills, but their eyes remain open and actively follow divers .

When a shark rests, they don't use their nostrils, they use their spiracles. If a shark tried to use its nostrils while resting on the ocean floor, they would suck up sand rather than water. Many scientists believe that this is one of the reasons why sharks have spiracles.

The spinal cord of the dogfish, instead of its brain, coordinates swimming so that a dogfish can continue swimming while it sleeps .

It is also possible that, in a similar way to dolphins, a shark can only sleep with parts of its brain.



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