The shark belongs to the type of chordate animals, the class of cartilaginous fish, the superorder of sharks (lat. Selachii). The origin of the Russian word “shark” comes from the language of the ancient Vikings, who called any fish with the word “hakall”. In the 18th century, dangerous waterfowl predators began to be called this in Rus', and initially the word sounded like “sharks”. Most of Sharks live in salt water, but some species also live in fresh water.

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

Thanks to species diversity The length of sharks varies greatly: small bottom sharks barely reach 20 cm, and the whale shark grows up to 20 meters and weighs 34 tons (the weight of an average sperm whale). The skeleton of a shark has no bones and consists only of cartilage tissue. The streamlined body is covered with scales with pronounced relief protrusions, the strength of which is not inferior to teeth, and therefore shark scales are called “skin denticles”.

The shark's respiratory organ is the gill slits located in front of the pectoral fins.

Shark heart support is too weak blood pressure, therefore, to stimulate blood flow, the fish should be in motion as often as possible, helping the heart with continuous muscle contractions. Although some species of sharks feel great lying on the bottom and pumping water through their gills.

The shark lacks a swim bladder, which all bony fish have.

Therefore, the shark’s buoyancy is ensured by the giant liver, which makes up almost a third of the body weight of the predatory fish, low density of cartilage tissue and fins.

The shark's stomach is very elastic, thanks to which it can accommodate a large number of food.

To digest food, the concentration of hydrochloric acid in the gastric juice is not enough, and then the sharks turn the stomach inside out, freeing it from undigested excess, and what is interesting is that the stomach does not suffer at all from numerous sharp teeth.

Sharks have excellent vision, 10 times greater than human vision.

Hearing is represented by the inner ear and picks up low frequencies and infrasounds, and also provides the balance function of predatory fish.

Sharks have a rare sense of smell and can smell odors wafting through the air and water.

Predators detect the smell of blood in a ratio of 1 to a million, which is comparable to a teaspoon diluted in a swimming pool.

The speed of a shark, as a rule, does not exceed 5 - 8 km/h, although upon sensing prey, the predator can accelerate to almost 20 km/h. Warm-blooded species - White shark and mako sharks cut through the water at speeds of up to 50 km/h.

The average lifespan of a shark is no more than 30 years, but sand dogfish, whale sharks and polar sharks can live more than 100 years.

The structure of a predator's jaw depends on the lifestyle and food consumed. The shark's teeth are long, sharp, cone-shaped, with which it can easily rip the flesh of the victim.

Representatives of the gray shark family are endowed with flat and sharp teeth, which allows them to tear apart the meat of large prey.

Tiger shark teeth

The whale shark, whose main diet is plankton, has small teeth up to 5 mm long, although their number can reach several thousand.

Horned sharks, which feed mainly on bottom food, have sharp small teeth in front and a rear row of large crushing teeth. As a result of wear or loss, the teeth of predatory fish are replaced by new ones that grow with inside graze.

How many teeth does a shark have?

Comb-toothed sharks have 6 rows of teeth on the lower jaw and 4 rows on the upper jaw with a total of 180-220 teeth. In the mouths of white and tiger sharks there are 280-300 teeth, which are located in 5-6 rows on each jaw. The frilled shark has 20-28 dental rows on each jaw, with a total of 300-400 teeth. U whale shark there are 14 thousand teeth in the mouth.

The size of shark teeth also varies from species to species. For example, the size of the teeth of a white shark is 5 cm. The length of the teeth of sharks that feed on plankton is only 5 mm.

White shark teeth

Where do sharks live?

Sharks live in the waters of the entire world's oceans, that is, in all seas and oceans. The main distribution occurs in equatorial and near-equatorial sea waters, near coastal waters, especially in reef areas.

It is worth noting that some species of sharks, such as the common gray shark and the bullnose shark, are able to live in both saltwater and fresh water, swimming in rivers. The average habitat depth of sharks is 2000 meters, in in rare cases they descend to 3000 meters.

What does a shark eat?

The food of sharks is quite varied and depends on the specific species and habitat. Most species prefer sea ​​fish. Deep sea sharks eat crabs and other crustaceans.

White shark hunting eared seals, elephant seals and cetacean mammals, the tiger shark swallows everything. And only 3 species - largemouth, whale and giant sharks eat plankton, cephalopods and small fish.

Types of sharks, names and photographs

Modern classification of these ancient fish, which existed hundreds of millions of years ago, distinguishes 8 main orders, forming about 450 species of sharks:

Carchariformes (gray, carcharid) sharks(lat. Carcharhiniformes)

This order unites 48 genera and 260 species. The following species are considered typical representatives of the order:

• Great hammerhead shark(lat. Sphyrna mokarran )

Lives in the waters of the Atlantic, Indian, Pacific, Caribbean and Mediterranean seas. The maximum recorded length of a hammerhead shark is 6.1 m. The leading edge of their hammerhead is almost straight, which distinguishes them from other hammerhead sharks. High dorsal has the shape of a sickle.

• Silk (Florida, widemouth) shark(lat. Carcharhinus falciformis)

Lives in the Mediterranean and Red Seas, found in the equatorial and adjacent latitudes of the world's oceans.

The widemouth shark is characterized by a rather dark color on the back of various shades of gray, blue, brownish-brown with a slight metallic sheen. Colors fade with age. The scales covering the skin of a shark are so small that they create the effect of their complete absence. It reaches 2.5-3.5 meters in length. The maximum recorded weight is 346 kilograms.

• Tiger (leopard) shark (lat. Galeocerdo cuvier)

Lives off the coast of Japan, New Zealand, USA, Africa, India, Australia. Tiger shark considered one of the most common shark species on Earth.

These large predators reach a length of 5.5 meters. The color of the leopard shark is gray, the belly is white or light yellow. Until the shark reaches two meters in length, transverse stripes similar to those of a tiger are noticeable on its sides. This is where its name came from. These stripes camouflage predatory fish from their larger relatives. With age, the stripes fade.

• Bull sharkor gray bull shark (lat. Carcharhinus leucas)

The most aggressive species of shark, common in tropical and subtropical oceans, you can often find this predatory fish in rivers and canals.

These huge fish have a spindle-shaped elongated body, characteristic of gray sharks, and a short, massive and blunt snout. Surface of the body blunt-nosed shark painted gray, belly white. The maximum recorded body length is 4 meters.

• Blue shark or blue shark (big shark or great blue shark)(lat.Prionace glauca )

It is one of the most common sharks on earth. The habitat of the blue shark is quite wide: it is found everywhere in the temperate and tropical waters of the World Ocean. reaches 3.8 meters in length and weighs 204 kilograms. This species has an elongated slender body with long pectoral fins. Body color is blue, belly is white.

Heterodonates (bull, horned)sharks(lat. Heterodontiformes )

The order includes one fossil and one modern gender, in which the following types can be distinguished:

• Zebra bull(Chinese bull, narrow-striped bull, narrow-striped horned) shark (lat. Heterodontus zebra)

Lives off the coast of China, Japan, Australia, Indonesia. The maximum recorded length is 122 cm. The body of the narrow-striped bull shark is light brown or white with wide brown stripes, in addition there are narrow stripes on the sides.

• Helmeted bull shark(lat. Heterodontus galeatus)

A rare species that lives off the coast of Australia. The skin of helmeted bull sharks is covered with large and rough dermal denticles. The color is light brown, with 5 dark saddle-shaped markings scattered across the main background. The maximum recorded length of the shark is 1.2 m.

• Mozambican bull(African horned) shark (lat. Heterodontus ramalheira)

The fish has a body length of just over 50 centimeters and lives off the coast of Mozambique, Yemen and Somalia. The base of the anal fin is located behind the base of the second dorsal fin. The main color of this species of shark is red-brown, with small white spots scattered throughout it. Maximum recorded length 64 cm.

Polybranchiformes (multibranched)sharks(lat. Hexanchiformes)

A primitive order representing only 6 species of sharks, with the most famous:

• frilled shark(cape bearer) (lat. Chlamydoselachus anguineus)

This shark has the ability to bend its body and attack its prey in a similar manner. The length of the frilled bat can reach 2 m, but is usually about 1.5 m in females and 1.3 m in males. The body is very elongated. The color of this type of shark is even dark brown or gray. They are distributed from the northern coast of Norway to Taiwan and California.

• Sevengill(ash sevengill shark, sevengill) (lat. Heptranchias perlo)

It is slightly more than 1 meter long and, despite aggressive behavior, is not dangerous to humans. It lives from coastal Cuban waters to the coasts of Australia and Chile.

The color of this species of shark ranges from brownish-gray to olive color, with a lighter belly. Some individuals of the ash sevengill shark have dark markings scattered across their backs, and may have light edging on their fins. Young sevengill sharks have dark spots on their sides, and the edges of the dorsal and upper lobes of the caudal fins are darker than the main color.

Lumniform sharks (lat. Lamniformes)

These are large fish, endowed with a body shaped like a torpedo. The order includes 7 genera:

• Gigantic (gigantic) sharks (lat. Cetorhinidae)

They have an average length of 15 m, but, despite their impressive dimensions, they do not pose a danger to people. The color is gray-brown with speckles. The caudal peduncle has pronounced lateral keels, and the tail of sharks is sickle-shaped. Giant sharks live mainly in Atlantic waters, Pacific Ocean, North and Mediterranean seas.

• Fox sharks (sea foxes) (lat. Alopias)

They are very long top part caudal fin equal to the length of the body. Sea foxes have a generally slender body with small dorsal and long pectoral fins. The color of sharks varies from brownish to bluish or lilac-gray, the belly is light. They grow up to 6 m in length, but are shy and try to avoid meeting people.

Distributed fox sharks in the waters North America and along the entire Pacific coast.

• Herrings(lamnovye) sharks (lat. Lamnidae)

These are the fastest sharks. A prominent representative of the family is the white shark, which has a body length of up to 6 meters. Thanks to their delicious meat, herring sharks are exterminated for commercial purposes and are also used as objects of sport hunting in the warm waters of the world's oceans.

• False sand sharks(lat. Pseudocarcharias)

Pseudocarcharias kamoharai – the only kind kind. These fish are distinguished by their peculiar body shape, reminiscent of a cigar. The average body length is 1 m; predators are not aggressive towards humans, but when caught, they begin to bite. These sharks live in the eastern Atlantic, Indian and Pacific oceans.

• Sand sharks(lat. Odontaspididae)

A family of large fish with an upturned nose and curved mouth. Slow and not aggressive, they are considered theoretically dangerous to humans, although recorded cases of cannibalism most likely relate to gray sharks, with which sand sharks are often confused.

Sand sharks are inhabitants of all tropical and many cool seas. Maximum length The body length of this type of shark is 3.7 m.

• Largemouth (pelagic)sharks(lat. Megachasma)

Family Megachasma represented by the only one and rare species Megachasmapelagios. Representatives of the species largemouth sharks They feed on plankton and are not dangerous to humans. The body length of this species is up to 6 m in length. These sharks swim off the coasts of Japan, Taiwan and the Philippine Islands.

• Scapanorhynchus sharks (goblin sharks)) (lat. Mitsukurinidae)

They represent 1 species, which received the popular nickname “goblin shark” for a long nose beak-shaped. Length adult is about 4 m and weighs just over 200 kg. A rare deep-sea shark species lives off the coast of Japan and Australia.

Wobbegong-like(lat. Orectolobiformes)

A squad consisting of 32 species of sharks, the brightest representative which is considered to be a whale shark (lat. Rhincodon typus), growing up to 20 meters in length. A good-natured animal that allows divers to pet it and even ride on its back.

Most species feed in shallow water on mollusks and crayfish. These sharks are found in warm waters of the tropical and subtropical zones.

Sawtooth sharks(lat.Pristiophoriformes )

The squad includes single family Saw sharks or sawnose sharks (lat. Pristiophoridae), which are distinguished by a long, flat snout with saw-like teeth. The average length of an adult sawnose shark is 1.5 meters. These are common predatory fish in the warm waters of the Pacific and Indian Ocean, as well as off the coast South Africa, Australia, Japan and several Caribbean countries.

Katraniformes (spiny) sharks (lat. Squaliformes)

A numerous order, including 22 genera and 112 species. Unusual representatives of the order are the Southern dogfish, sea dog, or marigold (lat. Squalus acanthias), which can be found in all seas and oceans, including Arctic and subantarctic waters.

Flat-body sharks (sea angels, squats) (lat. Squatina)

They are distinguished by a wide, flat body, resembling in appearance. Representatives sea ​​angels have a length of slightly more than 2 meters, lead mainly night look life, and during the day they sleep, buried in the mud. They live in all warm waters of the world's oceans.

One of the features of shark reproduction that distinguishes them from bony fish, is internal fertilization. The male fertilizes the egg directly in the female's body, introducing the genital organs - pterygopodia - into her cloaca. Pterygopodia are modified rays of the ventral fins of a male shark. Females do not have such organs. The further process of the birth of offspring in sharks proceeds according to three different scenarios, a description of which is given below.

Oviposition.

Oviparous sharks lay eggs that are similar in structure to the eggs of birds or reptiles. They have only an external difference - shark eggs do not have the usual oval or round shape - they are covered with various outgrowths, antennae or growths and their shape is often intricate.
However, these are the most ordinary eggs, from which shark fry eventually hatch. Like other oviparous animals, shark eggs contain many nutrients that allow the embryo to develop successfully.
The process of incubating eggs is quite long, sometimes more than a year. A baby shark, hatched from an egg, is capable of independent life.

The shell on shark eggs is formed during passage through the female's oviduct through the albumen and shell glands. The horny coating of shark eggs protects them from mechanical damage, dehydration and, in some cases, allows the eggs to be suspended on algae using special antennae and outgrowths.
Sometimes the sea throws shark eggs ashore, and they lie on the sand like weird sea ​​creatures. In ancient times, people called such finds “mermaid purses,” without finding a correct explanation for the appearance of these strange objects.

Many species of bottom sharks reproduce by oviposition; among free-swimming ones, one can note the polar (Greenland, ice) shark, which lays up to 500 eggs, the shape and size of which resemble those of a goose. The usual clutch of most oviparous sharks does not exceed one and a half dozen eggs.
About 30% reproduce by oviposition known species sharks



Ovoviviparity.

Reproduction of sharks by ovoviviparity - unique way, characteristic only of cartilaginous fish. Why nature invented such an unusual method of reproduction, scientists still cannot explain. Perhaps this is a dead-end branch of one of many evolutionary experiments.

Ovoviviparity differs from oviparity only in that the fertilized and formed eggs do not leave the female’s body, but remain in a special section of the oviduct, called the uterus, until the fry hatch. The mother's body in this case is a kind of incubator in which the eggs can develop in relative warmth (if this term can be applied to fish) and safety.
This method of reproduction differs from true viviparity in that embryos do not receive nutrients directly from the mother through a special connecting “canal” - the placenta, but have a supply of nutrition in their egg capsule, which is enough for the entire period of intrauterine development.
Most modern shark species reproduce by ovoviviparity. Among them are such sharks as Katran, a giant shark that gives birth to 1-2 cubs every two years, and a tiger shark that gives birth to up to 50 babies in one litter. The cubs are born well developed and able to exist independently.
You can watch a short video about how an ovoviviparous shark gives birth on this page.

Ovoviviparity of sharks is characterized by such a phenomenon as intrauterine cannibalism, when sharks that managed to hatch earlier from their eggs eat their brothers and sisters, who were late in hatching, right in the womb.

Viviparity.

During a live birth, an embryo develops in the female’s body, receiving nutrients directly from the mother’s body, by analogy with mammals.
The connection between the embryo and the female’s body does not occur immediately - for some time (sometimes up to several months), the embryo feeds on the supply of substances that are present in the yolk sac of the fertilized egg. The yolk sac then transforms into the placenta, which serves to connect the embryo with the mother's body.
It cannot be said that the most modern species of sharks reproduce in this way, since viviparity is inherent, for example, in the oldest shark - the frilled shark. A tenth of known shark species reproduce by viviparity, including all species of gray sharks, some hammerheads.

Among interesting features shark reproduction should be noted such a phenomenon as asexual reproduction or parthenogenesis. In some aquariums, there have been cases of reproduction of offspring by female sharks that were kept without males for a long time, i.e. the fact of fertilization was excluded. According to scientists, this is a kind of protective function that protects the shark species from extinction.

Sharks are a large group of animals belonging to the class Cartilaginous fish. There are 350 species of sharks in the world.

Their appearance and lifestyle are so diverse that it is difficult to recognize sharks in some representatives.

The famous sawfish is none other than the Japanese sawfish shark (Pristiophorus japonicus).

It is mistakenly assumed that all sharks are large predators. In fact, their size varies from 15 cm to 15 m and relatively small sharks are more common. Most species have an elongated torpedo-shaped body.

White shark (Carcharodon carcharias).

The muscular body of sharks has no bones at all; they are replaced by cartilage. In terms of hydrodynamic properties, sharks are the most advanced of all fish.

The dorsal fin rising out of the water indicates the presence of a shark in dangerous waters.

However, some sharks can have very non-standard appearance. The head of sharks is most often elongated with a characteristic pointed snout. The hammerhead shark's head has a specific shape that actually resembles a hammer.

The hammerhead shark's eyes are located at the ends of its snout. This vulnerable position of the eyes does not prevent her from being a dangerous predator.

The mouth of all sharks is located on the underside of the head.

The holes just below the shark's nostrils are the ampullae of Lorenzini. These are special organs that capture electromagnetic fields created by potential shark victims.

Sharks are exceptionally toothy fish. There are several hundred teeth in the mouth, arranged in several rows. As the outer row of teeth wears out, the teeth in the inner rows come to replace them.

With one bite of its sharp teeth, a shark can tear off a piece of flesh equal to the size of its mouth.

Shark teeth are modified scales. But shark scales are similar to teeth: each scale bears one or more pointed teeth, their shape can be different. The presence of these teeth gives shark skin a pronounced roughness. The skin of some sharks is even used as an abrasive. This is truly a fish that you can’t pet!

Leopard sharks (Triakis henlei) from California have mottled skin.

Behind the head, sharks have 5-7 gill slits. Sharks cannot actively move water through them, so they need to constantly move to breathe. True, some species of sharks have found a way to get rid of this burdensome duty: sharks lie down to rest in places with an active flow of oxygen-rich water. So, being motionless, sharks maintain their breathing.

Sharks are the oldest animals and one of the most primitive fish. But even here they present a surprise. Sharks reproduce differently than most fish. Have you ever heard of shark caviar? No, because sharks do not have caviar in the sense that we are used to thinking. Instead of laying many eggs, as most fish do, sharks prefer to lay just a few. But what “eggs” these are! Very large and covered with a special shell made from the secretions of the female’s oviducts, shark eggs are packaged in special capsules.

Cat shark eggs.

In the embryonic capsule of the shark, a dense yolk and a developing embryo are clearly visible.

In addition, their shape can be very bizarre and is designed to camouflage eggs from predators and attach them to aquatic vegetation.

A beached egg of an Australian bull shark (Heterodontus portusjacksoni) has a helical shape and thread-like projections for attachment to algae.

In some species viviparous sharks the eggs are retained in the female's body, where they are attached to the walls of the uterus with some semblance of a placenta and the embryos are fed through circulatory system mother. These sharks give birth to fully developed baby sharks, which from the first second begin an independent life. Who would have thought that “primitive” sharks could bear offspring almost like mammals. But the embryos sand shark went even further - they eat their brothers while still in the mother’s body!

Sharks are found in almost all seas and oceans tropical zone, but there are also cold-resistant species. Thus, the common katran inhabits the Black Sea, and the polar shark is found in the Arctic Ocean. The lifestyle of sharks is different: some species roam the open waters of the oceans in search of prey...

The shark found a school of fish in open ocean and quickly attacked him.

others prefer to look for it off the coast and in shallow reefs, while others lie at the bottom; There are also deep sea sharks.

A blacktip reef shark patrols shallow waters in search of prey.

The vast majority of species feed on medium-sized fish and categorically avoid attacking any large prey; some sharks feed on small bottom animals, but the largest of all fish - whale and basking sharks - are not predators at all.

The smile of the whale shark (Rhincodon typus) can rightfully be called welcoming, because it feeds only on small crustaceans.

These sharks are peaceful giants, filtering the water in search of plankton.

The basking shark (Cetorhinus maximus) obtains food in the same way.

Only some species of sharks hunt large prey - big fish, seabirds and mammals. But it is these species that have received the greatest fame.

White shark (Carcharodon carcharias) chasing a fur seal.

Sharks have a powerful arsenal of prey detection tools. They are sensitive to the slightest fluctuations in water and are able to smell the splash of wounded fish at a great distance. Sharks have an exceptional sense of smell and can taste blood diluted a million times in water! This scent unmistakably leads them to the trail of wounded animals.

The shark is baited with large fish.

Finally, sharks have a unique sense that distances and currents are powerless to overcome. They can detect electromagnetic fields created by living objects. To feel the movements of a dolphin or the beat of a heart fur seal the shark doesn’t even need smell, the animal will be detected in any case, and everything else is a matter of speed. Sharks are voracious and will stop at nothing in search of food - they can easily tear apart their comrade if she was injured, and inedible objects have also been found in their stomachs. But this is not the limit. There are known cases when sharks that were caught and gutted were caught a few minutes later... with their own guts! This, by the way, indicates the exceptional vitality of sharks: they are not sensitive to pain, they easily heal wounds (if they do not get caught in the teeth of their fellow creatures). Of course, all these cases are amazing, but they do not occur as often as they write about. In the vast majority of cases, shark aggressiveness is exaggerated. Only a few species are dangerous to humans, of which the great white shark is the best known.

The gray shark is one of the species dangerous to humans.

Shark attacks on humans are provoked in one way or another by people themselves. Tourists often feed small sharks themselves in the hope of capturing a rare shot of the predator. Following these fish, other sharks swim in for easy prey; their instincts are reinforced by the noisy splashing of swimmers, as well as the smell of food waste, which is always present to one degree or another near the beaches.

Divers pose with sharks in the background.

But people also hunt sharks. Some species of sharks are valuable commercial fish. They are mined for their meat, primarily for their delicious fins, which are used to make shark soup. Healing fat is extracted from the liver of sharks.

This 12-meter shark was caught in the net by accident. Besides commercial production Sport fishing for sharks is also practiced.

Meat from other parts of the carcass is used as canned food for pets. Durable shark skin is also used for industrial purposes. Sharks are also caught and kept in numerous aquariums as popular exhibits.

How is a shark born?

Aren't all animals born alive? There can be no doubt about this obvious fact, but birth cannot always be called a live birth. In animals there are 3 types individual development organism, or ontogenesis - larval, oviparous and intrauterine.

Most bony fish have a larval type, but sharks are characterized by oviparity and intrauterine birth, that is, viviparity. In many species, development is something between oviparous and intrauterine development - ovoviviparity.

What is the difference between viviparity and ovoviviparity?

In placental viviparity, the fetus receives oxygen and nutrients from the mother's blood with the help of special organs - the placenta and umbilical cord. This is typical for all mammals except oviparous mammals - the platypus and echidna.

Viviparity in sharks is the only example of placental viviparity in cold-blooded vertebrates.

In ovoviviparity, eggs develop in the female's genital tract, but there is no direct contact and exchange of substances between the organisms of the mother and fetus. The cubs hatch from the egg shell in the posterior part of the mother's oviduct, and only after this they are born.

During their development, they feed mainly on the nutrients of the yolk sac. In sharks, feeding such embryos is possible in several other very specific ways (oophagy and formation).

In addition to sharks, ovoviviparity is typical for species of lizards and snakes living in colder climates, some bony fish (swordtails, guppies, molynesias, gambusias), individual species toads Reptiles do not have any additional devices for feeding; their embryos, during ovoviviparity, receive only water from the female genital tract.

Watch video - Embryonic oophagy in sharks:

Who discovered viviparity in sharks?

Viviparity in sharks was first identified by the ancient Greek scientist and philosopher Aristotle. He could distinguish the egg capsules of viviparous and oviparous sharks by their appearance. Viviparous sharks produce eggs with translucent shells.

The 16th century French physician and zoologist Rondelet, in his book on ocean fish, included a drawing of a female shark connected by an umbilical cord to her baby. But the whole process was studied in most detail by the German zoologist Muller.

What are the features of viviparity in sharks?

At the beginning of development, embryos use the yolk, rich in high-calorie lecithin. Then part of the thin capsule of the egg and the wall of the already empty yolk sac form folds that tightly fit into the depressions in the wall of the uterus. Due to the formed folds, the surface area of ​​contact between the organisms of the mother and the calf increases. This complex complex is called.

Through the placenta, all the substances necessary for growth and development enter the blood of the fetus: amino acids for the synthesis of proteins, sugars and fats as sources of energy and construction material for cells.

In the opposite direction, females pass into the blood poisonous products exchange: ammonia, urea, carbon dioxide. A fairly long umbilical cord stretches from the placenta to the embryo, blood vessels which blood moves in both directions.

What types of sharks are viviparous?

Placental viviparity in 9% of: some hammerheads, some mustelids, and most carcharines (grays).

The American mustel shark gives birth to 10 to 20 young. The Cuban mustel shark, 30-40 cm long, usually develops 2 embryos in the uterus.

From the family of gray sharks, it brings from 5 to 7 sharks about 40 cm long.

Among placental viviparity only in some species. Viviparous have 6 to 9 young, and ovoviviparous have 30-40, but all of them are born with the same proportions as adults and up to 50 cm in size.

Watch video - Embryo of a viviparous shark:

Which sharks are ovoviviparous?

This is the most “popular” method of reproduction among sharks, because this is how 48% reproduce. cartilaginous fish. Of these, 27% feed only from the yolk sac, 2% from embryophagy and oophagy (), and 19% from royal milk (the so-called royal viviparity).

Watch video - Embryo of an ovoviviparous shark:

It turns out that many sharks bear young in the same way as mammals and humans. This means that in their biology they are not so far from us.

Is this why people of a certain character are called “sharks”?

The sexual life of sharks has been studied rather poorly - after all, observing them is dangerous to health, and technically difficult.

Pioneers of sex

It was previously believed that sharks were the ones who invented sexual intercourse: researchers assumed that they were the first animals to join, ahem, genitals to exchange genetic material. All other animals, and especially plants, reproduced either with the help of external fertilization, or without it at all - by division.

However, a couple of years ago it was proven that armored fish, who appeared before the sharks, also had sex, so the palm went to them.

On the other hand, those fish became extinct long ago, but sharks still exist, so we can say that of all the organisms living on earth, they have the greatest sexual experience. During research work in Western Australia several years ago, they even found the fossilized remains of giant prehistoric fish from a genus of extinct sharks of the Cretaceous period, captured in a very ambiguous pose.

The ancestors of modern predators were pressed tightly against each other with their bellies and clearly did not expect that sudden death would overtake them at the most inopportune moment. By the way, some species of these fish can be called not pioneers, but retirees of sex - female Greenland polar sharks, living in the waters of the North Atlantic, reach sexual maturity at the age of approximately 150 years! However, to be fair, it is worth noting that they live two or even three times longer.

Victims of violence

Can you tell on the subway in the morning which of those around you had sex last night? And those who last time Did you do this a month or two ago? How about six months? If you are not a psychic - which does not exist - then the result is predictable.

But if we're talking about about sharks, then the traces of a stormy night are immediately visible, and this is not at all a satisfied smile from the full toothed mouth - biologists can count the number of sexual intercourses a shark has by the scars on its body. The fact is that in most species of sharks there is an equal sign between sex and violence: the male literally brutally rapes the female, pouncing on her and holding her fins with his teeth. The female tries to fight back, so the gentleman also gets the worst of it.

Violence often occurs in groups: during the breeding season, males gather in schools and hunt females, who try to hide from them in shallow water. However, the male shark does not impregnate everyone; he can choose “the one” for quite a long time in order to pursue her for a long time and persistently.

It’s not just carnivorous species that behave this way: for example, giant sharks, which feed on plankton and won’t hurt flies, behave just as barbarically: scientists even believe that the huge teeth, which are not used for hunting or digestion, were left specifically for sexual needs.

Missionary position

Despite the fact that sharks are pioneers of sex, nature has never come up with anything better than the missionary position for them: the female and the male mate in the most classic position. Moreover, this is a prerequisite for sex, otherwise nothing will work out. When a male attacks a female, his task is to turn the lady onto her back at all costs, who fights back with all her might, using sharp teeth.

If the attempt to place the female on her shoulder blades is crowned with success, the job is done - she will fall into a state of tonic immobility, something between a trance and a coma. True, a shark needs to move in order to breathe, and in a coma it cannot do this, so more than 15 minutes of trance are fraught with death.

By the way, there are known cases when killer whales put sharks into a state of tonic immobility - not for sex, but just to have lunch.

No man? And it is not necessary

When sex turns from pleasure into torture, and you have to reproduce somehow, willy-nilly you have to look for other ways. And nature has found them for sharks: there are known cases where fertilization occurred in females without the participation of a male. True, in fact, the reason is not fear of violence, but long-term abstinence - parthenogenesis usually occurred in captivity, in aquariums, where females were kept alone for a long time.

It is believed that this defense mechanism, which protects sharks from extinction. These ancient predators also have another useful trick: they know how to store their partner’s sperm for several years and use it only at a favorable moment for themselves. Moreover, even if a shark is impregnated by several males, it will give birth to offspring from “that one” (although scientists just a few years ago put forward the theory that under such conditions, if several sharks are born, they may be from different fathers). The only thing that still remains a mystery is the mechanism for selecting the genetic material of a particular lover.

Eat your brother

Harsh fish have stern morals: many aquatic predators They eat both their own offspring and smaller relatives that accidentally turn up along the way. But sharks have gone the furthest: they are the only ones who practice fetal cannibalism. It is characteristic of ovoviviparous species that do not lay eggs in the sand, but carry them in utero.

At a certain stage, the embryo leaves the egg, and failed brothers and sisters who have not yet hatched become food for it. Is it any wonder that a shark is born a full-fledged predator, ready to tear and throw - unless he devours his own mother, of course.

To be fair, this rarely happens: nature turns on a protective mechanism, thanks to which the female after childbirth completely loses her appetite.