Since the release of the film Jaws in 1975, great white sharks have become one of the most recognizable shark species in the world. But, despite the increased attention to the person of this predator, many questions remain unanswered.

There are many difficulties associated with the study of sharks, and especially with the study of such giants as the white or tiger shark. Most species of sharks are either very rare or quite dangerous to be in open water with. For example, this type of shark reaches sexual maturity at 15 years old and at this age they are especially dangerous and aggressive.

Depending on the type there is three types of appearance into the world of baby sharks:

Laying eggs. The shark lays from two to about a dozen eggs in hidden places between rocks and algae. Shark eggs are similar in structure to the eggs of birds and reptiles, but have a rather unusual appearance; they are not characterized by an oval or round shape and are often covered with various growths and antennae.
And, despite all these are ordinary eggs, from which small sharks will soon hatch. The incubation process in some species can even last more than a year, and newborn sharks are already completely ready for independent life.
The shell of a shark egg protects from possible damage and dehydration, and sometimes helps the egg cling to stones with the help of specific antennae and growths.
Sometimes, due to a storm, shark eggs can be washed ashore. In ancient times, people, because they did not know the nature of the origin of these strange finds, called them “mermaid wallets.”
Thus, about a third reproduces known species sharks, among which it is worth noting the polar shark (Somniosus), which lays about half a thousand eggs at a time.

Ovoviviparity. This method is intermediate between laying eggs and the birth of already formed offspring. As with egg laying, the shark embryo develops in the egg, but by the time it hatches, the egg is in the mother's body. With this type of reproduction, the mother’s body plays the role of a kind of incubator, since nutrients shark embryo extracted from egg yolk, and does not feed on resources from the mother’s body.
This type of birth is characteristic of most shark species, including the tiger shark (Galeocerdo cuvier) and the basking shark (Cetorhinus maximus). The whale shark (Rhincodon typus) has also been proven to reproduce in this manner. Although the reproduction of whale sharks has been studied very little, scientists have found that there can be about twenty egg capsules in the female’s body. Eggs are very large sizes and reach a length of more than half a meter and 40 cm in width. One egg contains several embryos and their total number in the mother’s body can be more than 300. These giants reach sexual maturity very late, at about the age of 30 to 50 years, but they are real long-livers and favorable conditions live up to a hundred years.
Characteristic of tiger sharks is intrauterine cannibalism, the babies that hatch first eat their unborn sisters and brothers.

The embryo of a sand tiger shark becomes a full-fledged predator already in the mother's stomach.

More e unborn baby tiger sand sharks confirmed Darwin's stern principle of "survival of the fittest."
Scientists made this conclusion based on a study: they observed 15 pregnant sharks, each of which had up to 9 “eggs.” The first cannibal baby that hatched ate the rest of its relatives.

The sand tiger shark, or gray nurse shark, is a medium-sized shark, reaching 4 meters in length. Distributed in warm waters the entire world ocean, with the exception of the eastern part Pacific Ocean. It is endangered.
The shark's body is thick and wide, with two large fins on its back. Towards the head, the body narrows sharply, forming a sharp muzzle, the eyes are set close to the nose. The gill slits are not large. The back is gray or brown. The flat stomach is pale, almost white.

The sandbar shark is a voracious predator that feeds on bony fish, other sharks, squid and bottom-dwelling mollusks. The sand shark is quite slow and clumsy, especially during the daytime. It usually lives in the intertidal zone near the bottom and is often found at shallow depths and in shallow waters.
The shark got its name from its love of sandbanks. She is often seen close to the shore, on the beaches. In the surf zone, the shark slowly stalks its prey, which consists of small fish, squid, lobsters and crabs. She hunts after sunset. During the day, the fish is not active, preferring to sit out among the stones. At night, the shark has a voracious appetite. Sometimes fish gather in small schools to hunt together. Cases of several sharks attacking nets full of fish have been recorded.

They do not have a swim bladder, and in order to stay afloat, they swallow large number air.The sand tiger is the only shark that swallows air and holds it in its stomach to maintain buoyancy..

It reproduces by ovoviviparity, with the female giving birth to only one or two pups.
The gray nurse shark has two queens. Each fertilized female produces several eggs.
An interesting feature of this species is the so-called intrauterine ovophagy - the embryos eat eggs directly in the mother’s “uterus”, i.e. cannibalism from an early age.
The number of eggs in the ovary (in sand sharks only the right ovary functions) reaches 24 thousand (their total mass reaches 2.5 kg) and in its posterior part (“uterus”) they are located in egg capsules, each of which contains about 20 eggs.

Young sharks hatch in their mother's womb, and in order to survive, the strongest young sharks need to devour their brothers in the stomach.
Intrauterine nutrition of embryos begins quite early - at a length of 4-5 cm. Embryos with a length of 17 cm do not differ from adult fish in body shape and development of the dental apparatus.The baby shark has the same strong and sharp teeth, as well as a similar digestive system.

Today, there are known cases where intrauterine sharks ate not only neighboring embryos, but even fully formed small sharks.A large amount of egg yolk was found in the stomachs of such embryos, and once an even smaller embryo (4 cm long) was found - younger brother or sister.


Specialists for a long time observed a pregnant female and eventually came to the conclusion that the intrauterine baby shark, which has reached a size of twenty centimeters, begins to move quite freely and actively in the amniotic fluidamong the egg capsules completely and partially eaten by him.
At the end of pregnancy in the female's belly sand shark There are about twenty to twenty-five small sharks. Among them there is always one"dominant", developing faster than others,the strongest and most aggressive, which eats weaker sharksbefore birth (uterine cannibalism).


Thus, by the end of the gestation period, the shark develops two babies - one in each uterus. To maintain their strength, the mother continues to produce eggs, which are used as food for the young cannibals.This process is called internal cannibalism and is widespread among all shark species. As a result, one, maximum two small sharks are born, reaching a length of about one meter at the time of birth.


There was also another interesting feature: in 60% of cases, both surviving cubs belonged to the same father. (The genetic diversity of each female's offspring suggested that the shark mated with multiple males.)


Scientists believe that embryonic cannibalism contributes to faster and active development eyes and teeth of the surviving cub. The results of the study were published in the journal Biology Letters.
Thus, the primitive principle of survival and superiority over others of their own kind continues to exist even in such a cruel and exaggerated form. And, apparently, not without reason we're talking about specifically about sharks.

This reproduction, known in biology as " intrauterine cannibalism“makes every baby shark born very valuable for the future generation. Scientists plan to carry out artificial insemination of sexually mature females in order to maintain the population size of these interesting sharks. It is also believed that surgical removal of the hatchling and its subsequent artificial gestation can increase the number of sand tiger sharks.

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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.

Rising from the water dorsal 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 detect electromagnetic fields created by potential victims of sharks.

Sharks - exclusively 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 filament-like outgrowths for attachment to algae.

In some species of viviparous sharks, the eggs are retained in the body of the female, where they are attached to the walls of the uterus with a kind of 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 sand shark embryos go even further - they eat their fellows 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 North 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 are whale and giant shark- not predators at all.

Smile 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 a 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 shark species 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. In addition to commercial fishing, 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.

Representatives of the superorder Aciliformes reproduce offspring in several ways, depending on their biological species. Characteristic feature Shark reproduction is through internal fertilization.

This is how they differ from most other fish. For this purpose, males have a special reproductive organ - a pterygopodium. Juveniles can be born from eggs or through ovoviviparity. Also, in some varieties, true viviparity occurs.

Shark reproduction and egg laying

About a third of all these sea ​​predators reproduces by eggs or capsules. They are covered on top with a dense horny shell, unlike bird shells, and may not have a round, but an intricate shape. They may have outgrowths or antennae, with the help of which they linger at the bottom among algae or stones.

Inside the capsules there is a large amount of nutrients, due to which the embryo grows and develops. Incubation period can be long lasting, sometimes it continues more than a year. After its completion, a fully formed fry is born, which is capable of obtaining food as an adult animal.

This is how most benthic species reproduce, laying no more than 15 eggs at a time. Of the free-swimming species, the polar variety is known, which lays up to 500 capsules.

Shark Reproduction: Ovoviviparity

This method differs from true viviparity in that the fertilized eggs remain to develop in the female's body. When the fry are already sufficiently formed and developed, the female gives birth to fully formed living fry. But the juveniles receive nutrients not from the mother’s body, but from the capsule in which they are located.

Ovoviviparity allows you to save offspring much more effectively than with oviparity. The deposited capsules can become easy prey for predators, but when they are in the female’s body, they are reliably protected during their development.

Cases of parthenogenesis, or asexual reproduction, have also been recorded in these animals. In the absence of a male, the female is sometimes able to reproduce without fertilization.

This amazing feature allows these inhabitants of the sea to give birth to offspring in any conditions, and protects these fish from extinction.

Many species reproduce by ovoviviparity, for example, tiger and katran, which produce up to 50 fry in a litter.

Common catshark embryos

True live birth

This method is similar to mammalian reproduction, when the embryo is located in a special organ - the uterus, and is connected to the mother’s body through the placenta. The placenta appears over time. Until this moment, the embryo develops due to its existing yolk sac.

Shark reproduction, in which live young are born, is considered the most progressive method. This method is found only in cartilaginous fish and is not typical for bony fish.

Australian bull shark with egg

Such reproduction of their own kind is observed not only among the most modern species, but is also found among the most ancient. About one tenth of all these ocean predators living today reproduces in this way.

Viviparity as a method of reproduction for sharks is a progressive step in the evolutionary path of these species. At the same time, fully formed cubs appear, the survival rate of which is much higher than that of the larvae emerging from the eggs.

Therefore, if egg-laying fish can lay several hundred eggs, of which only a few survive to adulthood, then viviparous fish only need to give birth to several young to ensure the survival of the species.

Newborn baby California bloat shark

We can talk about sharks, the oldest sea creatures, for a very long time. And we will continue this conversation on the pages of new articles:

One of the reproductive features of sharks 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% of known shark species reproduce by oviposition.



Ovoviviparity.

Reproduction of sharks by ovoviviparity is a unique method inherent only cartilaginous fish. Why did nature invent this? unusual way reproduction of offspring, 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 special department 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. Then yolk sac 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 in, for example, the oldest shark- frilled. 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, long time kept without males, 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.