Sharks belong to the class of cartilaginous fish. The word "sharks" began to be used in the 18th century in relation to all aquatic predators.

Shark: description and photo. What does a shark look like?

There are over 500 different species of sharks. The squad is characterized by a variety of sizes, shapes and other features. For example, the smallest deep-sea small shark is considered to be the smallest, 17 cm long. One of the largest is the whale (up to 20 m in length). The same goes for weight - from 200 grams to several tens of tons.

Unlike bone fish, in sharks the skeleton is formed of cartilage. However, he is endowed with a sufficient level of rigidity. The skeleton includes 4 departments:

• spinal column (axial skeleton);
• unpaired fins;
• paired limbs (ventral and pectoral fins);
• skull.

The maneuverability and speed of movement of the fish is provided by several factors. The fish performs wave-like movements with the help of the body, tail and fins. The tail fin, which includes two blades, serves as the main “engine” for the shark, and also helps to set the direction of movement. The fins located on the sides allow you to increase the speed of movement and perform maneuvers.

Each shark species is distinguished by certain anatomical features of the tail. For example, a white shark moves very quickly, so the tail fin lobes are almost the same. In other species, the upper lobe is larger than the lower.

Interesting fact: when the shark slows down, plunges down or rises, the paired fins along with the dorsal help to maintain its balance. In this case, the fish is not able to swim in the opposite direction.

The body of the sharks is covered with very strong placoid scales. Each flake is a diamond-shaped plate with a spike on the protruding end. Shark scales are called skin teeth, because it is similar to teeth in terms of strength and structure. Scales fit tightly together. Because of this, at first glance it seems that the skin is perfectly smooth and even. But if you hold it with your hand in the opposite direction, from tail to head, a gross effect immediately becomes noticeable - the skin feels like sandpaper to the touch.

Shark muscles are represented by several muscle groups:

• cardiac;
• somatic (red and white, responsible for body movement);
• visceral (muscles in the vessels and internal organs).

The body of sharks is simple enough, and the metabolism is slow. Because of this, they can not be subjected to prolonged physical exertion. As a result of intense activity, an excessive amount of lactic acid accumulates in the body, which can adversely affect internal processes.

Sharks breathe oxygen coming from the water through the gills. The role of the respiratory system in them is performed by gill slits. They are located in front of the pectoral fins. The number of slots depends on the type of shark - from 5 to 7 pairs.

Due to the work of the heart, blood from sharks is transported through the gill artery into the vessels that are in the gills. There, the blood is saturated with oxygen and sent to the organs. However, to supply the whole body with enough oxygen, blood pressure is not enough. Therefore, the shark is in constant motion - muscle contraction increases blood flow.

Bone fish have a swimming bubble filled with gas. It is absent in sharks, so buoyancy is ensured by a huge liver, as well as a skeleton and fins. And sand sharks imitate a swimming bladder, filling the stomach with air.

Most sharks are cold-blooded with the exception of about 8 species. In white, blue and other sharks, individual parts of the body have a higher temperature than the environment. This allows them to move faster in cold water. Active muscles work to increase the temperature.

The shark stomach is U-shaped and can be easily stretched. The liver occupies about 30% of the total body volume. In addition to participating in the buoyancy processes, it serves as a kind of storage, which contains useful substances and energy reserves.

A shark for a very long time and gradually consumes the accumulated resources after eating, so it is able to starve for a long time. For example, a shark weighing 150 kg per year requires about 80-90 kg of fish. Periodically, fish have to clear the stomach of food debris. To do this, they twist it through the mouth, causing absolutely no damage to the teeth.

For sharks, the main sensory system is a well-developed sense of smell. They perfectly distinguish odors by passing water through the nostrils to the receptors.

Interesting fact: some sharks have receptors so sensitive that they recognize the smell of blood in a ratio of 1 to 1 million. That is, they can feel it at a great distance, dissolved in a large mass of water.

Vision in some species of fish is characterized by increased severity. In addition, they are able to distinguish between small details and some colors. The perception frequency is 45 frames per second. In some species, the eyelid blinks, in others it does not. To protect the eyes from damage, sharks of the second type roll them during the attack.

The organ of hearing is the inner ear, located inside the cartilage capsule. Predatory fish are able to catch low-frequency sounds, infrasound. The ear also helps maintain balance.

Interesting fact: The best shark hearing among white sharks.

Sharks have a sensitive organ - a side line that runs inside the skin along the side of the body. It responds to water fluctuations and allows fish to navigate in space, hunt and perform other vital functions.

How many teeth does a shark have?

The shape, size and number of teeth depends on what lifestyle the shark leads, what it eats. Teeth are the main weapon of these predators and their growth continues throughout the life cycle of fish. This is nothing more than a modified plakoid scale covering the skin.

Most sharks grow teeth in several rows - from 3 to 20 on both jaws. Each row includes about 30 teeth. Thus, an adult can have 200-15000 teeth. At the same time, they have no roots, so the change of teeth occurs quite often and imperceptibly for the predator.

The diet primarily affects the size and shape of the teeth. Most predator sharks have sharp cone-shaped teeth (about 5 cm long). If fish eat food in a hard shell, they need flat grinding teeth. Sharks hunting large prey have wide and serrated teeth. Plankton-eating fish have small teeth — only 3-5 mm.

The number of teeth in different types of sharks:

• white and brindle - 5-6 rows, up to 300;
• moustached - 5-7 rows, up to 500;
• hammerhead shark - 15-17 rows, up to 700;
• sand tiger - 42-28 rows, up to 1300;
• giant - 6-10 rows, up to 2000;
• whale - 18-20 rows, up to 15000.

Fish or mammal?

The term "mammal" refers to the feeding of young calves with milk. Sharks do not do this, therefore they are clearly categorized as fish. In addition, they breathe through the gills.

Many sharks in size catch up with large marine mammals, for example, some species of whales. However, this does not give a reason to classify them in this category.

The appearance of some species of sharks may also be misleading. For example, a shark-like shark is similar to an eel, a carpeted shark lives at the bottom, and a hammerhead shark is easily recognizable by the characteristic shape of its head.

Interesting fact: an unusual representative of sharks, carpeted, has an extraordinary appearance, swims poorly and most of the time lies at the bottom in anticipation of a fish swimming by.

Behavior and lifestyle

It is believed that sharks prefer to lead a solitary lifestyle and not form flocks.However, periodically they can be seen in groups, and quite numerous. Most often these are places with plenty of food. Sharks also live in groups during breeding.

Certain species of sharks prefer not to change their habitat. Others migrate, covering distances of thousands of kilometers. The migration system in fish is much more complicated than in birds. There is also a hierarchical system among sharks, according to which some species obey others. For example, despite the same size, the silk shark obeys the long-winged one.

Sharks do not always attack immediately as soon as they see the enemy. They communicate using movements. If an undesirable object is approaching, the predator can give a threatening signal, starting to move its fins more intensively.

The average speed of sharks is about 8 km / h. If necessary, this figure can increase to 19 km / h. Some species (white shark, etc.) make high-speed jerks of about 50 km / h. This ability is inherent in them due to the previously mentioned temperature difference.

According to new studies, sharks are able to show playfulness, curiosity, quick wit and other signs of intelligence. Often they overcome difficulties in the composition of the group.

How do sharks sleep?

For a long time, it was believed that sharks could not sleep, because they needed to constantly move to get oxygen. However, experts argue that at least some species of sharks (bottom) can be at rest for some time.

Interesting fact: only some sharks can remain stationary for a long time (during sleep), for example, a whiskered nanny shark. At the same time, they pump water through the gills and receive oxygen.

During sleep at the bottom of the shark, they do not close their eyes or use their nostrils. However, they may use spatter. Some species can sleep in motion, since the spinal cord is responsible for their movement. Another theory is the ability to turn off the cerebral hemispheres in turn.

Sharks can also “rest” in underwater caves, where there is a fairly strong current. It is curious that scuba divers found Caribbean reef sharks in one of these caves. They looked asleep despite the fact that this species is among the active swimmers.

How and what do sharks drink?

Strictly speaking, sharks are not required to regularly drink water in the direct sense of the word. Being in salt water, they absorb it constantly, and through the walls of the stomach the fresh component is absorbed into the blood and spreads throughout the body.

At the same time, the liquid in the body of the shark contains less salts than water in the environment. There is a physical process called osmotic pressure - a liquid with a lower concentration of salts rushes towards the liquid with a higher concentration. They contact through the skin of the fish. Thus, the body of sharks gets rid of excess salt.

Interesting fact: sharks that can inhabit both salt and fresh water (or only fresh) have the unique ability to rebuild the body for life in a particular environment. For example, a blunt shark.

How many sharks live?

The average lifespan of most sharks is about 30 years. However, there are species-centenarians. These include whale, spotted spiky, Greenland polar sharks that can live up to 100 years. Just the Greenland polar shark is considered the champion in terms of longevity. For example, the age of one of them would be estimated by scientists at 392 years with an error of 100 years. On average, the species survives up to 272 years.

Interesting fact: in 2019, scientists discovered the oldest and at the same time the largest shark, a representative of the species of Greenland polar. Estimated age is about 500 years. The fact is that for a year sharks of this species grow 1 cm in length. And the length of this individual was 5.4 m.

Longevity is directly related to shark teeth, because if a predator loses its main weapon, it will not be able to feed.

Where do sharks live?

Sharks are common in the waters of the oceans. Thus, they live in all oceans, seas. Cartilaginous fish prefer coastal waters, reef zones, equatorial and near equatorial waters.

Some species of sharks feel equally comfortable in both salt and fresh water. Therefore, they can swim in rivers. Such species include the blunt, common gray shark and others. On average, predators prefer a depth of about 2000 m, and sometimes swim 3000 m deep.

Sharks of the Black Sea

Due to the high hydrogen sulfide content in the waters of the Black Sea, the variety of sharks that cannot tolerate it is small. There are 2 species - katran and cat shark. These are small individuals that do not pose a danger to humans. The only thing - the body of the katran is studded with thorns, contact with which is fraught with negative consequences.

Rare cases are also known when predatory shark species swam into the waters of the Black Sea. For example, a large white shark can temporarily swim to the southern part of the Crimean coast and the western territories of the Krasnodar Territory.

What does a shark eat?

The diet of sharks depends on the specific species, as well as the habitat. In general, it can be called diverse. Most representatives are carnivores. Some species are unpretentious, therefore they feed on everything that comes in their way (for example, a tiger shark). The main part of the diet is fish, plankton, small mammals, crustaceans.

So, sharks that live on the bottom feed on crabs, other crustaceans. To do this, they have teeth that can bite through shells. Blue shark, mako, llama prey on sea fish while in motion. White shark prefers large fish and mammals. Whale, giant sharks, despite their impressive size, feed on plankton.

Interesting fact: whale shark can open its mouth by 4.6 meters.

Natural enemies of sharks

It is noteworthy that sharks exhibit predatory qualities from birth. For them, natural selection begins from the moment of birth. Cubs born earlier than others get rid of their brothers and sisters. Larger species also prey on recently born sharks.

Natural enemies of sharks:

• marlin;
• tagged fish;
• dolphins, killer whales;
• combed crocodile (freshwater).

Representatives of the marlin family can attack sharks, wielding their long and powerful “spear”. The same applies to a swordfish, which, when attacked by a shark, pierces the long nose of its gills.

Dolphins and killer whales are the main rivals of sharks in terms of food production, as the former feed on fish, the latter on large mammals. And this is the basis of the diet for shark predators. In addition, sharks suffer from bacteria and various parasites.

Shark breeding

Sharks are characterized by internal fertilization. At the same time, depending on the type, they can be:

• viviparous;
• ovoviviparous;
• oviparous.

Sharks have a long puberty - an average of about 10 years. The whale shark is capable of procreation only for 30-40 years of life. The incubation period also varies significantly - from a couple of months to 2 years.

Fish that breed in an oviparous manner lay 2-12 eggs. In this case, the eggs are covered with several shells. Including external horn-like. She protects offspring from predators. Cubs become independent immediately after birth.

In ovoviviparous fish, the calves are in the oviduct for some time. It is at this stage that natural selection acts and from the entire offspring there remains a maximum of 2 most powerful individuals. The size of the cubs varies depending on the species. The offspring of the tiger shark is about 50-76 cm long, and the white one and a half meters.

Population and species status

According to recent data, about 25% of all species of sharks are on the verge of extinction. The total number of fish is declining at a fairly high pace. There are several reasons for this:

1. Low reproductive ability - sharks are guided by the quality of the offspring produced, not the quantity. That is why, of all the cubs, only a few of the strongest remain.
2. Shark fishing, in particular illegal.
3. Reducing the amount of food that predators eat. Including a decrease in the number of mammals.
4. Wastewater pollution of the oceans. This is especially true for plastic.

It is worth noting that sharks, especially hungry, are prone to absorb everything in their path. Therefore, they are attracted to large piles of garbage floating in the ocean - they create fluctuations. Also, sharks are quite curious.

Shark fishing

More than 100 species of sharks are subject to fishing, as are many other fish. The fishing industry is interested in shark meat, fins, cartilage, liver and skin. The fishery is most actively carried out in the Atlantic Ocean, followed by the Indian and Pacific.

Up to 100 million individuals are caught each year. Prohibitions and restrictions on catch are gradually introduced, but its intensity is only increasing. Sharks are caught not only as a target fishing, but also by chance - during the catch of other fish.

There is a separate type of fishing - shark fin fishing. In some countries it is prohibited. Among other causes of shark fishing are increased danger on the beaches, the threat of a decrease in the population of other fish species.

Sharks attack humans

According to international statistics, the largest number of shark attacks on people recorded in countries such as the United States, Brazil, Australia, New Zealand and South Africa.

However, there are also unofficial data for which the ranking of the most dangerous countries is led by African countries. Near Ghana, Tanzania, Mozambique, populations of dangerous and fairly large sharks live. Most attacks occur in ocean waters, not in the seas.

Around the sharks are many myths. They are considered the most dangerous predators whose main goal is to attack people. This is only partially true. Sharks really are real predators and you need to follow all kinds of safety tips.

However, most sharks attack humans by mistake, confusing them with their true prey. Only a few species, such as white, tiger and other sharks, can attack without any reason. In general, concerns about these fish are greatly exaggerated.

Interesting fact: in the list of threats that await a person in the water, the shark takes the last place.

The maintenance of sharks in captivity

Only a few species of sharks can be found in captivity. Of greatest interest are known or, conversely, rare species. As a rule, they differ in large sizes, aggressive behavior. Catching such sharks, as well as transporting it is quite difficult. It is important not to damage them.

Also, experts will find it difficult to relocate an individual to an artificial reservoir. It should be spacious enough and durable, contain all the necessary equipment to make the shark feel safe. Support for normal functioning is required.

Sharks in culture

Sharks, as unique and interesting creatures, could not help becoming a part of culture for many peoples of the world. At a minimum, everyone must have seen Western films in which sharks act as real monsters.

But this is far from the whole role of fish in cultural heritage. They are mentioned in Greek mythology, Japanese, Polynesian culture. In particular, for the inhabitants of the Hawaiian Islands, sharks are not dangerous predators, but sea watchmen who guard the local people.

Australian aborigines regard them as gifts of nature intended for man.The Chinese consider sharks as an industry, namely, they consider them valuable in the field of food industry and traditional medicine.

In popular culture, a shark is an indispensable element of a horror movie or thriller about sea monsters. Examples of films with the participation of predator sharks:

• Jaws (1975);
• The Abyss (1977);
• The Deep Blue Sea (1999);
• "Sandbank" (2016) and others.

Shark species, names and photos

In total, there are about 500 species of sharks. They differ in a rather complicated classification, however, experts distinguish 8 main units (in parentheses are typical representatives of the unit):

• Karhariformes (giant hammerhead shark, silk, tiger, bull shark, blue);
• Lamiform (giant, white, fox, herring, pseudo-sandy, sandy, large-banded);
• Hazelike (zebra-like bovine, helmet-like, African horned);
• Multi-gill-like (lacrimal, seven-gill);
• Pyliform (pyloniferous);
• Wobbegong-like (whale);
• Katraobraznye (southern katran);
• Flat-bodied (Californian squat).

The most famous species

White shark characterized by aggressive behavior. The average age is about 70 years. Reaches 6 m in length or more, and such individuals weigh up to 2 tons. It features a good disguise in the form of skin in the upper part of the body in gray, brown, green shades. The lower body is much lighter. Has a highly sensitive sense of smell. Distributed in all ocean waters.

Whale shark reaches an average of 6-8 m in length. But this species is characterized by external diversity, therefore both small individuals and giants up to 20 m long are found. It is considered the largest shark. Despite the possible dimensions, it is harmless to people. The structure of the jaws and teeth is designed to capture small sea food along with water. The characteristic color is dark skin with large white spots on the back and sides.

Height giant shark - up to 15 m, weight - up to 4 tons. It ranks second in size. It also feeds on plankton. Can lead a solitary lifestyle or join in flocks. It features an unremarkable brown-gray color.

Great Shark grows to 5 m in length. It has a dark brown color in the upper part and light in the lower part. A characteristic feature is a large mouth, up to 1.5 m long, with small teeth. It feeds on small marine life, attracting them with luminous phosphorites.

Tiger shark - 4-meter individual with bright striped colors. But this color is peculiar only to young fish, while mature skin becomes gray. It is dangerous for people, because it moves quickly, has sharp teeth.

Bull shark distributed in all waters, including can swim in fresh water. It is also a danger to people. The average length is 3 m. It is distinguished by a muzzle of a special form, which attacks enemies. Therefore, it has a second name - dumb.

Black-headed shark looks more like a snake and is considered one of the ancient representatives, who retained its original appearance. In length reaches a maximum of 2 m. Due to the structure of the jaw, a sufficiently large fish is swallowed whole.

Mako Shark grows up to 3 meters, weighs about 100 kg. It is distinguished by aggressiveness, developed sense of smell, high speed. Danger to people. It has a gray-blue color with fair skin in the abdominal region.

Interesting fact: During the hunt, the Mako shark can jump 6 meters from the water.

Hammerhead shark has a characteristic feature - a flattened hammer-like head. It is dangerous for people. Some individuals reach 8 m in length.

Interesting fact: The location of the eyes of the hammerhead shark allows her to have a 360 ° view.

Fox shark reaches 5 m. It has a unique tail with a long upper lobe and a short lower. With the help of a tail, it stuns the fish and thus eats.

Mustached shark, also called canine because of its specific appearance - mustache and folds in the corners of the mouth. Length - up to a meter, with the tail occupying most of it. Swims quickly and successfully hunts small fish.

Reef - a shark with a thin body, a wide head. It grows to 1.5 m, and weighs only 20 kg. Usually has a dark gray color with rare spots. Distributed among coral reefs, lagoons, sandy shallow water.

Lemon shark differs in a yellow shade of skin with an admixture of pink and gray. It grows to 3 m in length. Often forms groups, especially young individuals. Demonstrates aggressiveness towards people.

Freshwater shark - A rare representative of fish that lives in fresh water all his life. Length - up to 3 m. It is dangerous both for people and for other animals approaching water. It has a gray-blue color with a light belly.

Dwarf shark - the smallest representative with a length of about 17 cm. It is considered poorly understood, as it belongs to deep-sea fish. Able to radiate green light through the eyes.

Cat shark - a small individual up to 1 m long with bright colors in the form of a dark shade with numerous spots. It features a flexible body and elegance. It is not dangerous for people.

The biggest sharks in the world

Species of sharks, characterized by particularly large sizes:

1. Megalodon is a long-extinct species, but according to the teeth found, the length was about 15 m, weight up to 40,000 kg.
2. Great whale shark - length 12 m and more, weight 21000 kg.
3. Giant shark - length 9-10 m, weight 4000 kg.
4. Tiger shark - length 7.5 m, weight 939 kg.
5. Great White Shark - length 6 m, weight 1500 kg.
6. Greenland shark - length 4-6, weight 1020 kg.
7. Hammerhead shark - length 5-6 meters, weight 844 kg.

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