The structure of a shark. External and internal structure of a shark

It is possible that of all the predators that live on planet Earth, sharks cause the greatest fear in people. It is difficult to find such a perfect and at the same time ancient organism. These are the oldest and most advanced killers that appeared in the waters of the World Ocean 420-450 million years ago. Since then, their appearance has remained virtually unchanged. But they were formed in the Jurassic period - a time when dinosaurs lived on earth, and the first birds were just exploring the heavenly space. The most famous and interesting shark species will be described in this article.

general characteristics

Many people don’t even realize how many species of sharks live in the world’s oceans. Meanwhile, there are approximately 350 of them, and each of them is unique in its own way. In this article, we will take a closer look at some sharks and at the same time find out which of them is most dangerous to humans.

Sharks are animals belonging to the superclass of fish. All types of sharks are predators because they use living creatures for food - from small planktonic inhabitants of the deep sea to large representatives of aquatic fauna. These fish are extremely hardy and tenacious. They are less sensitive to pain than other vertebrates. The organisms of sharks are so successfully honed by evolution that they managed to survive the struggle for existence with various, sometimes very strong, predators. Moreover, over centuries of evolution, these carnivorous creatures have hardly changed in the structure of their bodies and organs.

Not all types of sharks attack humans. However, they are all potentially dangerous. If you disturb fish during a hunt or provoke them in any other way, then the most harmless of them may well become aggressive. Considering their impressive size and capabilities, one can imagine what dire consequences this could have for a person.

Blacktip reef shark

There are a wide variety of shark species in the marine fauna. Photos of these predators give an idea of ​​how dangerous a one-on-one encounter with them can be. The blacktip reef shark is one of the smallest representatives of the family, since its normal length does not exceed two meters and its weight is forty-five kilograms. It is found at a depth of approximately thirty meters. This fish prefers to hunt in comfortable conditions, in the warm waters of the Pacific and Indian Oceans, among coral reefs.

Due to their modest parameters, these sharks are not dangerous to people. However, there are cases when they showed aggression, attacking careless swimmers. In all cases, this was associated with the smell of blood oozing into the sea from fish harpooned by humans.

Interestingly, the blacktip reef shark is a big sissy. Once, during transportation, due to an error by the carriers, the water in the aquarium was a couple of degrees below the usual minimum, and the fish died from hypothermia. Another unprecedented incident occurred during a show in a Brighton nightclub. An English comedian named Guy Venables dove into a tank of blacktip reef sharks. The result was sad. An adult twelve-year-old fish died from fright.

Whiskered nurse shark

There are marine inhabitants with very interesting habits. Nurse shark is bottom fish, living at a depth of six meters. Usually it reaches 2.5-3.5 meters in length, but four-meter individuals are also found. These fish live in schools of up to forty individuals. They feed on octopuses, crustaceans, mollusks, sea urchins, etc. Unlike the rest of their fellow sharks, the nurse shark does not bite the caught prey, but rather “sucks” it into itself. At the same time, a peculiar sound is heard, reminiscent of a kiss. Apparently, this is why the bottom predator received such an “affectionate” name.

This shark is active at night and completely calm during the day. Under rocks, in grottoes and crevices, you can stumble upon a whole accumulation of fish, lazily lying on top of each other in massive stacks.

Sand tiger sharks

These representatives of the marine fauna have a rather terrifying appearance, but at the same time they are distinguished by their peaceful nature. They attack people solely in self-defense. It must be said that the tiger shark uses an original method to maintain its own buoyancy: it swallows air and retains it in its stomach. Sand sharks are found in warm waters, mainly off the Australian coasts. The largest population of these predators is observed off the coast of North Carolina, in the area of ​​sunken ships.

These days, the sand tiger shark is at risk of extinction. It is listed in the International Red Book.

Hammerhead shark

Frighteningly large and incredibly aggressive, hammerhead sharks are striking in the shape of their heads. It looks like a hammer with a pair of eyes on the edges. Scientists are still arguing about this fact. Some people think that the strange shape of the animal’s head is the result of centuries of evolution, others believe that this is a consequence of a sudden bizarre mutation.

Frightening photos of large hammerhead sharks can be found in any book about the predatory inhabitants of ocean waters. Their appearance is terrifying. It is reassuring that similar fish can be found in temperate and warm waters of the Atlantic, Indian and Pacific Oceans at a dizzying depth of 300-400 meters. Aggressive creatures feed on different types of fish, crustaceans, octopuses, squids and other inhabitants of the deep sea.

Hammerhead sharks reach 3.5-4.2 meters in length and weigh about 450 kg. Interestingly, these fish find their prey using special receptors that are sensitive to electromagnetic pulses. The predator feels electrical discharges the size of one millionth of a volt!

Since the size of the hammerhead shark is large, scientists classify it as particularly dangerous to humans. But these animals do not attack humans unless absolutely necessary. However, there is documentary evidence that voracious predators can be dangerous to people. In Long Island in 1805, three hammerhead sharks were caught simultaneously. The remains of a human torso were found in the stomach of one of them.

The giant hammerhead shark is listed as critically endangered in the International Red Book.

Whale shark

One of the largest living representatives of fish is the whale shark. The largest specimen ever measured measured 13.7 meters in length and weighed approximately 12 tons. Despite its enormous parameters, this ocean dweller consumes only plankton and other similar small organisms. The fish filters its prey by sucking in water through its huge mouth.

Tiger shark

These are real tigers of the sea - strong, fearless, elusive. They are on the list of the most aggressive representatives of marine fauna, attacking humans without hesitation. The tiger shark got its name because transverse stripes can be seen on its sides. They disappear when the animal reaches two meters in length. An adult specimen grows up to five meters; there are larger specimens. The weight of a sea tiger is from 570 to 750 kg. The lifespan of this predatory fish is 30-40 years.

The tiger shark fearlessly dives to depths of up to one kilometer. It lives in many seas and oceans, but prefers to stay near the coast in tropical and subtropical heat zones.

Bull shark

In all the seas of the planet there are species of sharks that are very dangerous to humans. Photos of some of them are presented in this article. The bull shark is a large fish (4 meters long) that lives approximately 27-28 years. It occupies an “honorable” third place on the list of man-eating sharks. This is a very aggressive animal, claiming to be an all-powerful predator, an ideal killer. It is almost impossible to escape from such a shark.

Bloodthirsty hunters attack in the early morning or at dusk, often in shallow water (only 0.5 m - 1 m). The behavior of bull sharks is impossible to predict. They are capable of swimming nearby quite calmly for a long time, and then suddenly attacking a swimmer. And this attack can have the most unpredictable consequences.

Great white shark

“White Death” is the name given to this large predator that lives in the surface waters of all the main oceans of the planet. Due to its serious size (length - 6 meters and weight - up to 3000 kg), this shark is recognized as the largest predatory fish of our time. These carnivorous creatures move as fast as a torpedo. They are capable of reaching speeds of up to 24 km/h.

In the wide mouth of the white shark there are 280-300 triangular teeth arranged in several rows. This powerful animal has spent millions of years honing its killing skills, and there is no escaping it. However, the population of the white predator is constantly declining. On earth it is represented by only 3,500 copies.

Sharks of the Mediterranean Sea

The Mediterranean basin has all the conditions for living predatory fish: warm water, plenty of varied food. There are approximately 40 species of sharks here, 15 of which pose a secret or obvious threat to humans. Thousands of tourists vacation on the shores of this warm sea every year, so encounters between people and powerful carnivorous fish are inevitable. In fairness, it is worth noting that this is the calmest shark-dangerous area on the planet. Over the last century, sharks Mediterranean Sea Only two dozen people were killed. This is an insignificant number, but behind each such case there is a huge tragedy. Almost all of the predators listed above in this article live in the Mediterranean basin. Here it is quite possible to meet a white or bull shark, tiger and sand predators come across. Even the incredible hammerhead fish occasionally visits the rich waters of the Mediterranean. Therefore, everyone should remember that vigilance at foreign resorts is necessary to preserve one’s own health, and perhaps even life.

Black Sea shark

Carnivorous fish are also found in the friendly Black Sea. The shortfin spiny shark (katran) is considered safe for humans. It has small parameters: it reaches two meters in length and weighs from 8 to 25 kilograms. The katran, a photograph of which is presented in this article, lives in the depths Black Sea waters, where he hunts horse mackerel and other small fish. Only in the off-season (autumn and spring) does this shark swim to the coast. The real threat is the spines of this sea creature. They protrude from the animal's dorsal fins and are covered in highly toxic mucus. A person burned by this poison will develop a painful swelling that will last for several days. Otherwise, the katran shark is a completely peaceful inhabitant of the Black Sea.

Sharks on Sakhalin

In September 2014, a great white shark was found entangled in a net. There is nothing surprising in this, only this happened on Sakhalin, where such fish had never been found. At various times, several cases of shark attacks on humans were recorded in Primorye and in the southern Kuril Islands. In 2004, a predator attacked a diver and seriously injured him, but the man managed to escape. Seven years later, in Primorye, a carnivorous fish encroached on the life of a 25-year-old resident of the city of Vladivostok. The man lost both arms, but remained alive. Sakhalin sharks are very rare, but a collision with them does not bode well for a defenseless person.

Sharks - scary predators which are gradually disappearing from the face of the earth. Man is primarily to blame for this. Possessing knowledge inaccessible to other inhabitants of the planet, he poisons the water and soil, making them uninhabitable. No wonder ecologists say that the most dangerous creatures on globe- these are people. Let's remember this when blaming sharks for senseless bloodthirstiness and robbery.

Evolution has worked hard on these creatures, providing them with adaptation mechanisms that allowed them to bypass other ancient species at historical turns. Sharks appeared 450 million years ago and are rightfully considered the most advanced aquatic animals.

Description of sharks

Selachii (sharks) belong to the superorder of cartilaginous fishes (subclass elasmobranchs) with a characteristic appearance - a torpedo-shaped body with an asymmetrical caudal fin and a head whose jaws are studded with several rows of sharp teeth. The Russian transcription of the term goes back to the Old Icelandic “hákall”: this is how the Vikings once called all kinds of fish. In Rus', the word “akul” (m.r.) began to be used in relation to any aquatic predators around the 18th century.

Appearance

Not all, but many sharks have a torpedo body and an oval-conical head, which helps them easily overcome the hydrodynamic resistance of the water column, gaining decent speed. The fish swims by making wave-like movements with its body/tail and using all its fins. The tail, which serves as a rudder and engine, consists of 2 blades, the upper one of which includes the spinal column.

Side fins add speed and maneuverability, and also “steer” during turns, climbs and dives. In addition, the paired fins, together with the dorsal one, are responsible for balance during sudden stops and somersaults. Paradoxically, the shark, which has a complex arsenal of fins, never learned to “back up,” but it did learn some funny tricks.

This is interesting! Epaulette sharks walk along the bottom on pectoral and ventral fins, like legs. Small glowing sharks (no more than half a meter in height) “flutter” in the water like hummingbirds, quickly bringing their pectoral fins together and spreading them apart.

The cartilaginous skeleton is additionally strengthened with calcium in areas with greater load (jaws and spine). By the way, the lightness of the skeleton is another reason for shark mobility and resourcefulness. The predator’s thick skin, composed of placoid scales resembling teeth (in strength and structure), also helps the predator cope with the resistance of the environment. It appears smooth if you move your hand from head to tail, and rough as sandpaper if you move your hand from tail to head.

Mucus from glands in the skin reduces friction and promotes high speed. In addition, shark skin contains a lot of pigment, which is responsible for the specific coloring of each species. Fish, as a rule, mimic the terrain, and are often decorated with stripes/spots to match the general background of the bottom or thickets. Most sharks have darker tops than their bellies, which helps them camouflage when viewed from above. And the light shade of the belly, on the contrary, makes the predator less noticeable to those who look for prey from the depths.

Fish or mammal

Sharks are aquatic animals from the class of cartilaginous fish, which includes close relatives of these predators, stingrays. Aquatic mammals (whales, seals, dolphins and others) living next to sharks and even somewhat resembling the latter do not belong to their family clan. Even sharks endowed with an extraordinary appearance still remain fish, such as, for example, the frilled shark, whose body contours are similar to a sea snake or an eel.

Carpet and squat sharks, which live on the bottom, are distinguished by a flat body with an inconspicuous sandy color, hiding them among bottom plants. Some wobbegong sharks have acquired leathery growths on their snouts (“wobbegong” is translated from the Aboriginal language of Australia as “shaggy beard”). The hammerhead shark, whose name is influenced by the unusual T-shape of its head, also stands out from the crowd.

Character and lifestyle

It is commonly believed that a shark plows the ocean in splendid isolation, without creating numerous schools. In reality, predators are no strangers social behavior: They gather in huge groups during breeding seasons or in places with an abundance of food.

Many species tend to be sedentary and sedentary, but some sharks migrate quite far, covering thousands of miles annually. Ichthyologists suggest that the migration pattern of these predatory fish is more complex than that of birds. Sharks have an interspecific social hierarchy, especially in terms of “distribution” of food rations: for example, the silky shark is certainly subordinate to the long-winged shark.

This is interesting! The predator has a couple of ways to take a nap: do it while moving (after all, it is controlled not so much by the brain as by the spinal cord) or turn off each hemisphere alternately, like dolphins.

The shark is constantly hungry and extremely voracious, which is why it spends days and nights chasing suitable prey with virtually no rest. Ichthyologists recorded the sounds made by sharks as they cut through the water column and the crunching of their jaws, but came to the conclusion that these fish do not exchange sounds, but communicate through body language (including the position of the body and the rotation of the fins).

Movement and breathing

Sharks are doomed to constant movement - they need oxygen, but they (like most cartilaginous fish) do not have gill covers that push water through the gills. This is why the predator swims with its mouth slightly open: this way it captures water (to get oxygen) and removes it through the gill slits. Some sharks still manage to slow down, organizing a short rest for themselves in areas with strong underwater currents or pumping water through their gills (for which they inflate their cheeks and use squirters). It also turned out that certain species of sharks, mostly bottom-dwelling ones, can breathe through their skin.

In addition, an increased concentration of myoglobin (respiratory protein) was found in the muscle tissue of sharks, due to which they, unlike bony fish, are able to withstand the load caused by constant movement. The cerebellum and forebrain, which are classified as the most developed parts of the brain, are responsible for complex movements and coordination in space.

The role of the heart and liver

The temperature of a shark's body is usually equal to the temperature of its native water element, which is why these fish are called cold-blooded. True, some pelagic sharks are partly warm-blooded, since they are able to increase their own temperature due to the intense work of the muscles that heat the blood. The heart, located in the thoracic region (near the head) consists of 2 chambers, the atrium and the ventricle. The purpose of the heart is to pump blood through the gill artery into the vessels located in the gills. Here the blood is oxygenated and supplied to other important organs.

Important! The heart does not have enough power to maintain the blood pressure needed to distribute oxygen throughout the huge body. The shark's regular muscle contractions help stimulate blood flow.

The shark has a multifunctional and quite impressive (up to 20% of the total weight) liver, which is assigned several tasks:

• cleansing the body of toxins;
• storage of nutrients;
• replacement of a missing swim bladder.

Thanks to the liver, sharks stay afloat and almost do not feel pressure drops during sharp ascents and descents.

Sense organs

Sharks have terrible vision - they distinguish contours, but are not able to enjoy the color diversity of the world. Moreover, sharks may not notice a stationary object, but will perk up when it moves. Because predators attack with their heads, nature has equipped their eyes with protective devices such as skin folds or nictitating membranes. The inner and middle ears are designed to perceive even low-frequency vibrations (inaccessible to human hearing), for example, the movement of water layers.

Ampullae of Lorenzini also help in finding prey, as they detect minor electrical impulses given by the prey. These receptors are found on the front of the head (there are especially many of them in the hammerhead shark) and on the body.

This is interesting! Sharks have an amazingly acute sense of smell, 10 thousand times more receptive than a human, which is explained by the developed anterior lobes of the brain, which are responsible for the sense of smell, as well as the presence of nostril pits/grooves on the snout.

Thanks to the latter, the flow of water to the nostrils increases, the receptors are washed and read information about odors. It’s not for nothing that a swimming shark constantly twists its nose and turns its head: this is how it tries to figure out where the alluring aroma is coming from.

It is not surprising that even a blinded predator can easily find fishing spots. But the shark goes into the greatest frenzy when it smells blood - a few drops dissolved in a standard pool are enough for this. It has been noticed that certain species of sharks have a so-called “aerial” sense of smell: they catch odors distributed not only in water, but also through the air.

How long do sharks live?

Almost all representatives of the superorder do not live very long - approximately 20–30 years. But among sharks there are also long-livers, crossing the 100-year mark. These include types such as:

• spotted spiny;
• Greenland polar.

The third, by the way, has become an absolute record holder not only among its relatives, but among all vertebrates. Paleogeneticists estimated the age of the 5-meter-long specimen to be 392 years (±120 years), which led to the conclusion that the average lifespan of the species was 272 years.

This is interesting! A shark’s life is controlled by its teeth, or rather, by their tireless “rotation”: from birth to death, the predator changes up to 50 thousand teeth. If this did not happen, the mouth would lose its main weapon, and the fish would simply die of hunger.

The teeth are renewed as they fall out, moving out (as in a conveyor belt) from the inside of the mouth. The structure of the teeth/jaws is determined by the type of diet and lifestyle: most sharks have teeth set on cartilage and resemble sharp cones. The smallest teeth are in species that eat plankton: no more than 3–5 mm in the whale shark. Carnivorous species (for example, sand sharks) use long, sharp teeth that easily penetrate the flesh of the prey.

Nature has equipped bottom-dwelling sharks, such as heterotoothed sharks, with crushing (flat and ribbed) teeth capable of splitting shells. The tiger shark has wide and serrated teeth: they are needed to cut and tear the meat of large animals.

Types of sharks

Their number is still a question: some ichthyologists put the figure at 450, while others are confident that the species diversity of sharks is much more representative (about 530 species). The only thing the opponents agree on is the number of squads that unite all the sharks on the planet.

By modern classification There are only eight such groups:

• carchariformes– an order with the maximum (among sharks) diversity of species, some of which are prone to oophagy;
• heterodentate– a detachment of bottom-dwelling sharks with nocturnal activity, having a dense body, 2 dorsal spines and one anal fin;
• polybranchiformes– includes 2 families, distinguished by the shape of the body: torpedo-shaped in polygill sharks and eel-shaped in frilled sharks;
• laminated– the group is dominated by huge pelagic sharks with a torpedo-shaped body;
• wobbegong-shaped- inhabit warm and tropical seas. All except the whale shark live on the bottom;
• sawtoothed– they are easily recognized by their long, saw-like snout with many teeth;
• katran-shaped– found at great depths throughout the world, including latitudes near the poles;
• squatinous- with a short muzzle and flattened body they resemble stingrays, however, shark gills open not from the bottom, but from the sides.

This is interesting! The most inconspicuous among the sharks is the small dogfish (17–21 cm long), and the most impressive is the whale shark, growing up to 15–20 m.

Range, habitats

Sharks have adapted to life throughout the oceans, and some species (including the common gray shark) periodically enter estuaries fresh rivers. Sharks prefer equatorial/near-equatorial waters, as well as coastal waters with a rich food supply. Typically, predators stay at a depth of 2 km, occasionally descending to 3 km or even lower.

Shark diet

Sharks have wide gastronomic preferences, which is explained by the structure of the stomach: it is incredibly stretchable and is capable of not only digesting prey, but also storing it in reserve. The main component of gastric juice is hydrochloric acid, easily dissolving metal, varnish and other materials. It is not surprising that some sharks (for example,) do not limit themselves at all in food, swallowing all objects they encounter.

This is interesting! The tiger shark has a little trick that saves you from the consequences of uncontrollable gluttony. The predator knows how to turn its stomach inside out through its mouth (without damaging the walls with sharp teeth!), spewing out indigestible food and then rinsing it.

In general, the diet of sharks looks something like this:

• mammals;
• fish;
• crustaceans;
• plankton.

Reproduction and offspring

Sharks, like all cartilaginous fish, reproduce by internal fertilization, when the male introduces sexual products into the female's body. Coitus is more like rape, since the partner bites and firmly holds the partner, who is subsequently forced to heal love wounds.

Modern sharks are divided into 3 categories (according to the method of birth of offspring):

• oviparous;
• ovoviviparous;
• viviparous.

All methods of reproduction are aimed at preserving species, as they reduce embryonic/postembryonic mortality. Oviparous sharks (over 30% known species) lay from 1 to 12 large eggs, hanging them on algae. The thick shell protects the fruit from dehydration, damage and predators. The largest clutches are observed in polar sharks, laying up to 500 (goose-like) eggs.

In ovoviviparous sharks (more than 50% of species), the egg develops in the mother’s body: the offspring hatch there. Pregnancy lasts from several months to 2 years (katrans), which is considered a record among all vertebrates. Just over 10% of current sharks give birth to “ready” babies (from 3 to 30). By the way, newborns often die in the teeth of their own mother if they do not have time to swim to a safe distance.

This is interesting! In females in captivity, cases of parthenogenesis were observed, when offspring appeared without the participation of males. Ichthyologists believe this defense mechanism, designed to preserve the population of the species.

The topic of our article is sharks, the internal structure of which we will consider in the following order:

• Skeleton and muscles;
• Nervous system: brain and sense organs;
• Circulatory system;
• Breath;
• Digestion;
• Genitourinary system.

Skeleton and muscles of a shark

Let's start studying the internal structure of sharks with the musculoskeletal system, which includes the skeleton and muscles. The skeleton of predatory fish consists of a skull, an axial skeleton, a skeleton of paired fins and their belts, and a skeleton of unpaired fins.

The skull is represented by the braincase and the visceral region, including the jaws and gills.

The braincase consists of cartilage tissue that protects the brain on all sides. Only in the upper part there remains a hole (fontanel), which is not overgrown with cartilage during the formation of the skull, but remains covered with a connective tissue film.

Behind the jaws there are paired cartilaginous arches of the gills, connected by unpaired cartilages - copulas.

The skeleton of the shoulder girdle is represented by a semi-ring-shaped cartilage, on the sides of which there are processes for connection with the three basal cartilages of the pectoral fins. From the basal cartilages there are three rows of thinner radial cartilages and from the latter there are thin filaments of elastin.

The pelvic girdle is simpler in structure and has a cartilaginous plate lying in front of the cloaca slit, to which one row of radial fin cartilages is attached. Elastin threads also extend from the radial cartilages.

Watch the video: Anatomy of a shark - dissection and study of the internal structure

Unpaired fins (caudal, anal and dorsal) have a skeleton consisting only of radial cartilage and elastin filaments. The spine extends into the dorsal fin and into its upper section.

U spiny sharks there is no anal fin, but there is a dorsal fin, which gave the name to the family.

The muscular system of the shark’s internal structure is very developed and consists of myomeres (muscle segments) surrounded by a connective tissue membrane.

The muscular system is abundantly supplied with blood, since movement is life for a shark. After all, in order for the blood to return back to the heart, only the pressure created by the heart is not enough. And muscle contractions come to the rescue.

Watch video - Building muscular system white shark:

Shark nervous system and sensory organs

The nervous system is represented by the brain and spinal cord, from which nerves extend to organs and tissues.

It is still believed that vision in elasmobranchs is poorly developed, but is compensated by smell and sensitivity to electrical impulses.

At the bottom of the oral cavity there is a small fold of mucous membrane - the tongue, which does not have muscles. Then the food enters the pharynx.

To prevent food from falling out of the gills, sharks have cartilaginous outgrowths on their gill arches - gill rakers.

The pharynx passes into the esophagus, through which food enters. The stomach of some sharks has the ability to “turn inside out,” freeing itself from undigested and inedible food debris.

The stomach is joined by the small intestine, which passes into the large intestine and then into the rectum. The large intestine has a spiral valve, which is an outgrowth of the mucosa that increases the absorption surface.

Read more in the article

A protrusion extends from the large intestine - the rectal gland, which secretes an odorous secretion to attract individuals of the opposite sex.

Sharks also have very large sizes(which partially performs the function), gallbladder and pancreas.

Remains of food enter the cloaca, where the ducts of the genitourinary system open.

Genitourinary system of sharks

Among the organs of the urinary system, sharks have kidneys, which in males act as an appendage to the testis, and ureters.

The reproductive system of sharks is represented, as we have already mentioned, by testes in males, from which seminiferous tubules with an extension at the end extend into the cloaca, and by ovaries in females.

Watch the video: Shark genitourinary system - structure and operation

It is worth noting unique feature internal structure - absence of kidneys and urinary tract. Urine and the ammonia contained in it are washed out by the blood and excreted directly through the skin of the predator.

All types of sharks have a similar mechanism for thoroughly processing urine, but polar sharks treat their urine most carefully.

The fact is that, for example, the urine of land mammals contains many valuable trace elements and fresh water, which they wastefully remove through the urinary tract.

Sharks in this regard are very economical. Every drop of fresh water, as well as a share of valuable microelements, is extracted from urea before everything unnecessary is released through the pores in the skin.

This careful attitude of the predator to its urea has led to the extreme saturation of polar shark meat with ammonia, giving it an unpleasant odor.

Sharks are characterized by internal fertilization. A mature egg falls into the abdominal cavity and rolls into the funnel of the oviduct, where fertilization occurs. The oviduct contains shell glands that form the shell of the egg.

At the end of the oviduct there is an extension - a kind of “uterus” in which the eggs ripen.

During ovoviviparity, sharks hatch from the eggs in these “wombs,” which may even be immature eggs.

If the shark is not viviparous, but oviparous, then the maturation of the embryo and its hatching from the egg will occur in the external environment.

Scientific discovery of 2016

Sharks are well-known predators of marine waters. Species diversity ancient fish represented unusually widely: small representatives reach 20 cm, and large ones – 20 m in length.

Common Shark Species

Only shark names will take up more than one page. The classification identifies 8 orders of fish, including approximately 450 species, only three of which feed on plankton, the rest are predators. Some families are adapted to live in fresh waters.

How many types of sharks actually exists in nature, one can only guess, because sometimes individuals are found that were considered hopelessly lost to history.

Shark genera and species are united into orders:

• carchariformes (carcharidae);
• heterogeneous (bovine, horned);
• polybranchiformes (polybranchials);
• lamniform;
• wobbegong-shaped;
• sawnose;
• katran-shaped (spiny);
• flat-bodied representatives.

Despite the diversity of predators, sharks are united by structural features:

• the basis of the fish skeleton is cartilage tissue;
• all species breathe oxygen through gill slits;
• absence of a swim bladder;
• acute sense of smell - blood can be sensed several kilometers away.

Carcharine sharks

Found in the waters of the Atlantic, Pacific, Indian Oceans, in the Mediterranean, Caribbean, Red Seas. Dangerous species sharks. Typical representatives:

Tiger (leopard) shark

Known for its prevalence in coastal areas, India, Japan, and Australia. The name reflects the color of the predators, similar to the tiger pattern. The transverse stripes on a gray background persist until the shark grows over 2 meters long, then they turn pale.

Maximum size up to 5.5 meters. Greedy predators swallow even inedible objects. They themselves are a commercial object - the liver, skin, and fins of fish are valued. Sharks are very prolific: up to 80 live-born pups appear in one litter.

Hammerhead shark

Lives in the warm waters of the oceans. The record length of the giant specimen was recorded at 6.1 m. The weight of large representatives is up to 500 kg. Shark appearance unusual, massive. The dorsal fin is sickle-shaped. Ahead of the “hammer” is almost straight. Favorite prey: poisonous stingrays and seahorses. They bear offspring once every two years, 50-55 newborns. Dangerous for humans.

Hammerhead shark

Silky (Florida) shark

Body length is 2.5-3.5 m. Weight is about 350 kg. The color includes different shades of grayish-blue with a metallic sheen. The scales are very small. Since ancient times, the streamlined body of a fish has terrified sea ​​depths.

The image of a cruel hunter is associated with stories of attacks on divers. They live everywhere in waters with water heated to 23°C.

Silky shark

Snout shark

Variety gray sharks, known for the greatest aggressiveness. Maximum length is 4 m. Other names: bull shark, tub head. More than half of all human victims are attributed to this predator. Lives in coastal areas of Africa and India.

The peculiarity of the bovine species is in the osmoregulation of the body, i.e. adaptation to fresh water. The appearance of a blunt-nosed shark at the mouths of rivers flowing into the seas is common.

Blunt shark and its sharp teeth

Blue shark

The most common variety. Average length up to 3.8 m, weight more than 200 kg. It got its name from the color of its slender body. The shark is dangerous to humans. It can approach the shores and go to great depths. Migrates across the Atlantic.

Blue shark foraging for food

Hedgetooth sharks

Typical bottom inhabitants are of medium size. Many species are called bulls, which creates confusion with dangerous gray individuals called bulls. The squad has rare species sharks, not dangerous to humans.

Zebra shark

Lives in shallow waters off the coast of Japan, China,. Narrow stripes Brown on a light background they resemble a zebra pattern. Dull short snout. It poses no danger to humans.

Zebra shark

Helmet shark

A rare species found off the Australian coast. The skin is covered with rough teeth. Unusual color of dark spots on a light brownish background. The average length of individuals is 1 m. They feed on sea urchins and small organisms. It has no commercial value.

Mozambican shark

The length of the fish is only 50-60 cm. The red-brown body is strewn with white spots. A little-studied species. Feeds on crustaceans. It lives on the coasts of Mozambique, Somalia, and Yemen.

Polygill sharks

The order has existed for hundreds of millions of years. An unusual number of gill slits and a special shape of teeth distinguish the patriarchs of the shark tribe. They live in deep water.

Sevengill (straightnose) shark

Slender body of ash color with a narrow head. The fish is small in size, up to 100-120 cm in length. It exhibits an aggressive character. After catching it, it tries to bite the offender.

Frilled shark

The length of the flexible elongated body is approximately 1.5-2 m. The ability to bend resembles a snake. Color grey-brown. The membranes of the gills form leather bags similar to a cloak. Dangerous predator roots from the Cretaceous period. The shark is called a living fossil for its lack of signs of evolution. The second name was received for the numerous folds on the skin.

Lumniform sharks

The torpedo shape and powerful tail allow it to swim quickly. Large specimens are of commercial importance. Sharks are dangerous to humans.

Fox sharks

A distinctive feature of the species is the elongated upper lobe of the caudal fin. Used as a whip to stun prey. A cylindrical body, 3-4 m long, is adapted for high-speed movement.

Some types sea ​​foxes They filter plankton and are not predators. Thanks to taste qualities meat have commercial value.

Giant sharks

Giants, more than 15 m long, are second in size after whale sharks. The color is gray-brown with speckles. Lives in all temperate waters of the oceans. They do not pose a danger to people. Feeds on plankton.

The peculiarity of the behavior is that the shark constantly keeps its mouth open, filtering 2000 tons of water per hour while moving.

Sand sharks

Inhabitants of the deep and explorers of coastal zones at the same time. You can recognize the variety by its upturned nose and the frightening appearance of its massive body. Found in many tropical and cool seas.

The average length of the fish is 3.7 m. In general, sand sharks, which are harmless to humans, are confused with gray predators, known for aggression.

Mako shark (black tip)

There are short-finned varieties and long-finned relatives. In addition to the Arctic Ocean, the predator lives in all other oceans. It does not go deeper than 150 m. The average size reaches 4 m in length and weighs 450 kg.

Despite the fact that many existing shark species dangerous, the gray-blue predator is an unsurpassed deadly weapon. Develops colossal speed in pursuit of schools of mackerel, schools, and sometimes jumps above the water.

Goblin shark (brownie, rhinoceros)

Random loot unknown fish at the end of the 19th century, approximately 1 m long, led scientists to the discovery: extinct shark species Scapanorhynchus, thought to have existed 100 million years ago, is alive! The unusual snout above the head makes it look like a shark. An alien from the past was found again several times after almost 100 years. Very rare inhabitants.

Wobbegong sharks

The peculiarity of the order is the unusually smooth and rounded shapes of predators among their relatives. Different types of sharks The variegated coloring and bizarre growths on the body bring them together. Many representatives lead a bottom-dwelling lifestyle.

Whale shark

An amazing giant up to 20 meters long. Found in reservoirs of tropical zones and subtropics. They do not tolerate cold water well. A beautiful, harmless predator whose food consists of mollusks and crayfish. Divers can pat him on the back.

It amazes with its grace and unique appearance. Small eyes on a flattened head hide in a fold of skin in case of danger. Small teeth are arranged in 300 rows, their total number is approximately 15,000 pieces. They lead a solitary life and rarely form small groups.

Carpal wobbegong

IN strange creature it is difficult to recognize a relative of the ocean predators that terrify all aquatic inhabitants. The aerobatics of camouflage consists of a flat body covered with some kind of rags.

It is very difficult to recognize fins and eyes. Sharks are often called mustachioed and bearded due to the fringe along the contour of their heads. Thanks to unusual appearance bottom sharks often become pets in public aquariums.

Zebra shark (leopard)

The spotted color is very reminiscent of a leopard, but no one will change the ingrained name. The leopard shark is often found in warm sea ​​waters, at a depth of up to 60 meters along coastlines. The beauty is often captured by underwater photographers.

Zebra shark on photo reflects an atypical representative of his tribe. The smoothed lines of the fins and body, rounded head, leathery protrusions along the body, and yellow-brown color create a spectacular appearance. Does not show aggression towards humans.

Sawtooth sharks

A distinctive feature of the representatives of the order is a jagged outgrowth on the snout, similar to a saw, and a pair of long antennae. The main function of the organ is to search for food. They literally plow up the bottom soil if they sense prey.

In case of danger, they swing a saw, inflicting wounds on the enemy with sharp teeth. The average length of an individual is 1.5 m. Sharks live in warm ocean waters, off the coasts South Africa, Japan, Australia.

Short-nosed sawnose

The length of the sawtooth outgrowth is approximately 23-24% of the length of the fish. The usual “saw” of its relatives reaches a third of the total body length. The color is gray-blue, the belly is light. With side blows of the saw, sharks injure their victims in order to then eat them. Leads a solitary lifestyle.

Dwarf saw-nos (African saw-nos)

There is information about catching dwarf (body length less than 60 cm) sawbills, but there is no scientific description. Types of sharks very small sizes are rare. Like their relatives, they lead a bottom life on silt-sandy soil.

Golden sharks

Representatives of the order live almost everywhere in all sea and ocean waters. Since ancient times, spines have been hidden in the fins of katran-shaped fish. There are thorns on the back and skin, which can easily cause injury.

None of them are dangerous to humans. The peculiarity of fish is that they are saturated with mercury, so eating spiny sharks is not recommended.

Types of sharks of the Black Sea include katran representatives, the indigenous inhabitants of this reservoir.

Southern siltworm

It lives at a depth of up to 400 m. The body is dense, spindle-shaped. The head is pointed. The color is light brown. Shy fish are harmless to humans. You can only get hurt on thorns and hard skin.

Heavy Sludge

Massive body of a fish with characteristic shape silt swallowers. Lives at great depths. Little studied. Rare specimens of the shortthorn shark were caught in deep-sea catches.

granular shark

A common type of fish at a depth of 200-600 m. The name appeared due to its original shape, similar to sandpaper. Sharks are not aggressive. Maximum dimensions reach 26-27 cm. Color black-brown. There is no commercial value due to the difficult production and small size of the fish.

Flat-bodied sharks (squat sharks, angel sharks)

The shape of the predator resembles a stingray. The length of typical representatives of the order is approximately 2 m. They are active at night; during the day they bury themselves in the mud and sleep. They feed on bottom organisms. Squat sharks are not aggressive, but react to provoking actions of swimmers and divers.

Squatins are called sand devils for their method of hunting from ambush with a sudden rush. The prey is sucked into the toothy mouth.

The most ancient creatures of nature, living in the ocean for 400 million years, are many-sided and diverse. A person studies the world of sharks like a fascinating book with historical characters.