At the moment, about 400 species of sharks are known: from the smallest (15 cm in length) to giants (18 m in length). They have their own characteristics, but there are also common features that are inherent in almost all species:
- Sharks are not stupid animals, the ratio of their brain to body weight reaches that of some mammals.
- Life expectancy is 30 years.
- Sharks have a highly developed sense of smell and hearing, and also have an unusual sense organ - Lorenzini's electroreceptors.
- They pick up electromagnetic waves.
- Shark cartilage skeleton.
However, there are a number of features that distinguish sharks from other animals and give great mystery: for example, how a shark sleeps, how it eats, moves and hunts.
The structure of the jaw
Huge teeth 5 cm long are terrifying. On average, a predator has 4-6 rows of teeth, but some individuals can have up to 20. When the front tooth falls out, a tooth from the back row moves to replace it. By the way, losing teeth for a shark is a common thing. For 10 years, an individual tiger shark is able to change up to 24 thousand teeth. The process of change occurs with such frequencydue to the structure of the jaw: the teeth are attached directly to the gum.
No swim bladder
Unlike other fish, sharks do not have a bladder. Therefore, the animal is constantly in motion. If you stop working with your tail, the shark will sink to the bottom. Despite the absence of a bladder in all individuals, there is a species of predator that can stay afloat without additional effort. We are talking about a sand shark: it is able to swallow air and keep it in itself for several hours.
How a shark sleeps
Answering the question of how a shark sleeps, you need to understand that it does not have sleep as such. Rather, the process can be called rest. Predators living near the shore or in shallower bodies of water equip a place to "sleep" in underwater caves. There, the shark seems to be sleeping - it lies at the bottom without moving.
How do sharks sleep in the oceans? Sharks that live in deep waters almost never sleep, because, having stopped working with their tail and fins, they will dive to a great depth not intended for them. It is easier for those individuals who live at a depth all the time - they can find time for "sleep". Speaking of whether sharks sleep, you can safely give a negative answer.
Prey hunting
Sharks are very bloodthirsty. Feeling the slightest smell of blood, they immediately go to search for the victim. In hunting, a developed sense of smell helps them. It only takes 1 gram of fish blood per 1 million grams of water to feel the prey. However, if you close the nostrils of a predator, then there will be no reaction to the victim, and the shark will swim past.
When a shark has already smelled its prey, it may start to have "hungry rabies". At this moment, the predator manifests a special rage, it crushes and swallows everything in its path. In the end, the stomach, which is able to expand several times, may contain many unusual things.
As for sharks that prefer plankton and small fish, these species pass more than one hundred liters of water through themselves to feast on their favorite food. They are not dangerous to humans and are peaceful.
Interesting facts about sharks
Sharks are rather unusual creatures that you can talk about endlessly. They exist for millions of years and at the same time perfectly adapt to any living conditions. Predators have outlived the dinosaurs and are clearly not going to die out. Here are some more interesting facts about sharks:
- Baby sharks are born with teeth.
- Sharks can see colors.
- The main food of polar sharks are polar bears and deer.
- Some species can jump up to 10m high.
- To saturate the body, an animal needs 3-14% of its own body weight per week.
- There are long-lived sharks that can live up to 100 years.
Learning how sharks sleep, how they eat and how they exist, you can understand that this is a unique species of fish with a long history.
