Blue shark in natural conditions

The role of the teeth is performed by the special scales of sharks, which grow both throughout the body and in the mouth. Sharks usually have 45 main teeth and several rows of spare ones. A shark can grow 6000 teeth in a year. Teeth-scales on the skin swirl the water so that it does not create friction with the body. Sharks do not have heavy bones, but have the same strong, but light cartilage, and therefore sharks do not need a swim bladder. And if other fish stay in the water like an airship, then sharks move in the water like planes in the air, using their fins as elevators, and the dorsal fin serves as a stabilizer.
To date, scientists know about the existence of 526 species of sharks, which have a length of 17 centimeters to 20 meters. The body temperature of 99% of shark species is always equal to the temperature of the water, therefore these fish are called cold-blooded. But there are 6 species of sharks that are partially warm-blooded. They are able to raise their body temperature due to the energetic work of muscle tissues, which heat the blood.
Etmopterus perryi is considered the smallest shark - it is a deep-sea katra-shaped shark of the Etmopterus family (Etmopterus), which is found in the Atlantic Ocean only off the coast of Venezuela and the Caribbean Sea off the coast of Colombia at depths of 300 to 500 meters. She never comes close to the coast. The maximum size of the male of such a shark is 21 centimeters, and the female is 17 centimeters.