Study of the lenses of the eyes of the Greenland shark ( Somniosus microcephalus) showed that the age of its large individuals is about 400 years. Moreover, such a life expectancy is the rule for this species, not the exception. Apparently, the Greenland shark is the longest-lived living vertebrate.
Death, oddly enough, is a relatively new invention of evolution. The first inhabitants of planet Earth, bacteria and archaea, were potentially immortal. Single-celled creatures They can, of course, die from a variety of external causes, but they do not have a programmed death, which necessarily completes each life cycle and leads to the formation of a corpse. It appears along with multicellularity associated with sexual reproduction. Back in 1914, a fairly famous zoologist, Professor Evgeniy Aleksandrovich Shultz, wrote about this:
« Nature had every means to make the individual immortal, but she chose death for him. Instead of constantly rejuvenating individual organs - through the rejuvenation of their cells - she chose to rejuvenate the entire organism with the help of a single cell. She took away our immortality and gave us love in return.».
It looks like Schultz was right. It does not follow from any known laws of nature that any multicellular organism must necessarily grow old and die. Now, for example, we know that individual coral polyps can live for more than four thousand years, and there is no reason to believe that this age is the limit (E. B. Roark et al., 2009. Extreme longevity in proteinaceous deep-sea corals). True, this has been established for polyps in which the individual is part of the colony. Independent organisms, and especially those with complex nervous systems, as a rule, have a limited lifespan - different for each species.
For example, it has been shown that in mammals the life expectancy is within inverse relationship on metabolic rate and in direct dependence on the relative size of the brain (M. A. Hofman, 1983. Energy metabolism, brain size and longevity in mammals). In other animals such dependencies are probably more heterogeneous and complex. However, among mammals there are special cases. The most famous of them is the naked mole rat ( Heterocephalus glaber), an African rodent that is eusocial, like social insects. A colony of mole rats in many ways resembles a termite mound - it consists of a “queen” (reproducing female), her two or three “husbands” and several dozen “workers” of both sexes who do not reproduce. At the same time, naked mole rats practically do not age and can live more than 30 years; for mammals of this size, this is a unique case (see Genome of the naked mole rat - the key to the secret of longevity? "Elements", 11/11/2011). The absence of aging, leading to a huge increase in life expectancy - ten times compared to mice and rats - allows working individuals, who do not spend resources on their own reproduction, to take care of many generations of newborn descendants of the queen in a row. But the most interesting thing in this story is the ability to “turn off” aging if there is an evolutionary “request” for this. Naked mole rats show us that this possibility exists. And here a huge field for research opens up.
To what values can the individual lifespan of a complex multicellular animal - for example, a vertebrate - reach in principle, and is there any natural limit here at all? To find out, you must first understand how long vertebrates actually live in nature. And this is not always easy. But little by little the facts accumulate. A new interesting piece of information on this topic was recently presented to scientists by a Greenland polar shark (Fig. 1).
Meanwhile, Greenland sharks can also be six meters long (judging by reference books, their maximum recorded length is 640 cm). What’s even more interesting is that it has long been known that female Greenland sharks reach sexual maturity at a length of about four meters. And now, based on the collected data, it can be argued that they reach this length at the age of approximately 150 years. Only then does the Greenland shark become an adult.
So, it turns out that the Greenland shark is the longest-living vertebrate in the world. Previously, this was considered the bowhead whale, which can live to at least 211 years (see A new database on the life expectancy of vertebrates AnAge has appeared on the Internet - the most complete and accurate, “Elements”, 06/15/2009). Interestingly, this estimate was also obtained by analyzing the chemical composition of the eye lens (J. C. George et al., 1999. Age and growth estimates of bowhead whales ( Balaena mysticetus) via aspartic acid racemization). But the Greenland shark, so to speak, lives even slower. In general, there is nothing surprising here; the new data fits well with well-known trends: with a large size and a obviously low metabolic rate (in an icy ocean, a cold-blooded animal cannot have another), slow development is quite natural. But the specific age figures obtained are, of course, impressive. I wonder if some vertebrates might have even more of them?
The Greenland shark is recognized as the longest living vertebrate. The age of the sea predator can reach almost 500 years.
Scientists have concluded that the longest-living vertebrate known on the planet today is the Greenland Arctic shark (Somniosus microcephalus).
The BBC reports this.
The researchers came to these conclusions after studying 28 individuals of the Greenland shark.
To determine the age of the sharks, scientists used radiocarbon dating. They conducted radiocarbon dating of the nucleus of the lens of shark eyes and found that average duration their lifespan is approximately 272 years.
Wherein Scientists estimated the age of the oldest individual at 392 years.
Experts also found that Greenland sharks grow extremely slowly - only one centimeter per year, and Greenland sharks reach sexual maturity at 150 years of age.
The full results of the study are contained in an article published in the journal Science.
Lead author of the study, marine biologist Julius Nielsen from the University of Copenhagen, said: “We assumed that we were dealing with an unusual animal, but the fact that the sharks turned out to be so old was a surprise to us.”
The scientists' findings refuted scientific ideas about the longest-living vertebrate. Previously it was believed that such a record holder is the bowhead whale, whose age is estimated at 211 years.
The Greenland polar shark, or the small-headed polar shark, or the Atlantic polar shark (lat. Somniosus microcephalus) is a species of the genus of polar sharks of the family Somniosa sharks of the order Katraniformes.
Lives in the waters of the North Atlantic. The range extends further north than that of other sharks.
Reproduces by ovoviviparity. These slow-moving sharks feed on fish and carrion. They are objects of fishing.
Maximum recorded length 6.4 m.
The species was first scientifically described in 1801 as Squalus microcephalus. The specific name comes from the Greek words κεφαλή - “head” and μικρός - “small”. In 2004, it was determined that previously thought to be Greenland sharks living in the South Atlantic and Southern Ocean, they are a separate species, Somniosus antarcticus.
These are the northernmost and most cold-loving of all sharks. They are widespread in the north Atlantic Ocean- off the coast of Greenland, Iceland, Canada (Labrador, New Brunswick, Nunavut, Prince Edward Island), Denmark, Germany, Norway, Russia and the USA (Maine, Massachusetts, North Carolina).
They are found on the continental and island shelves and in the upper part of the continental slope from the surface of the water to a depth of 2200 m. In winter in the Arctic and North Atlantic, Greenland sharks are found in the surf zone, in small bays and river mouths near the surface of the water. In summer they stay at a depth of 180 to 550 m.
In lower latitudes (Gulf of Maine and North Sea), these sharks are found on the continental shelf, migrating to shallow waters in spring and fall. The temperature in their habitat is 0.6–12 °C. Sharks tagged under the ice off Baffin Island at the end of spring preferred to stay in the depths in the morning, and by noon they rose to shallow water and spent the night there.
Greenland sharks are apex predators. Their diet mainly consists of fish such as small sharks, rays, eels, herring, capelin, char, cod, sockeye salmon, catfish, lumpfish and flounder. However, sometimes they also hunt seals. Teeth marks on the bodies of dead seals off the coast of Sable Island and Nova Scotia suggest that Arctic Greenland sharks are their main predators in winter.
On occasion, they also eat carrion: cases are described when the remains of polar bears and reindeer were found in the stomachs of polar sharks. They are known to be attracted to water by the smell of rotting meat. They often gather in large numbers around fishing boats.
Greenland sharks are one of the slowest sharks. Their average speed is 1.6 km/h, and their maximum speed is 2.7 km/h, which is half as much maximum speed seals. Therefore scientists for a long time They were amazed at how these clumsy fish were able to hunt such fast prey. There is evidence that Arctic Greenland sharks lie in wait for sleeping seals.
The Greenland shark is recognized by scientists as the longest-living vertebrate species. Biologists believe that the animal can live about 500 years.
In 2010-2013, scientists measured the body length and radiocarbon dating of the eye lens of 28 Greenland sharks. As a result, it turned out that the longest of them (more than five meters) was born 272-512 years ago (the Greenland shark, according to scientists, grows on average by one centimeter every year). Such a high life expectancy of sharks is explained by low metabolism, for example, females reach sexual maturity at 150 years.
TMAO, found in the tissues of Greenland sharks, helps stabilize enzymes and structural proteins that would otherwise not function properly due to cold temperatures and high pressure. Although in summer the temperature of Arctic waters can reach 10 and even 12 °C, in the middle of winter it can drop to −2 °C. Under such conditions, even the most stable proteins cease to function normally without chemical protection.
The body of polar fish produces glycoproteins as antifreeze. Arctic sharks accumulate urea and TMAO to prevent the formation of ice crystals and stabilize proteins. At a depth of 2200 meters the pressure environment is about 220 atmospheres or 220 kilograms per square centimeter. It is not surprising that the concentration in the tissues of Greenland sharks protective substance TMAO is very high.
Attacks on humans attributed to Greenland sharks are extremely rare. They live in cold waters where it is almost impossible to meet a person. However, there was a recorded case in which a Greenland shark followed a ship in the Gulf of St. Lawrence. Another shark chased a group of divers and forced them to the surface of the water. Some fishermen believe that Greenland sharks damage gear and destroy fish, and regard them as pests. Therefore, when caught, they cut off the tail fin of the sharks and throw them overboard. Once caught, Greenland sharks offer virtually no resistance.
From the mid-19th century until the 60s of the 20th century, fishermen in Greenland and Iceland caught up to 50,000 Greenland sharks per year. In some countries, fishing continues to this day. Sharks are hunted for their liver oil. Raw meat is poisonous due to its high urea and TMAO content, causing poisoning not only in humans, but also in dogs. This poisoning is accompanied by convulsions and can be fatal.
A traditional Icelandic dish is prepared from polar shark meat through long-term processing. hakarl. Sometimes these sharks are caught as bycatch when fishing for halibut and shrimp. The International Union for Conservation of Nature has assigned the species a conservation status of Near Threatened.
The shark belongs to the type of chordates, the class of cartilaginous fish, the superorder of sharks ( 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 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 shark's skeleton 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.
The shark's heart maintains too little blood pressure, so to stimulate blood flow, the fish must move 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.
For food digestion concentration of hydrochloric acid there is not enough gastric juice, 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.
Rumor presented inner ear and picks up low frequencies and infrasounds, and in addition provides a balance function for 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 total number 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. The whale shark has 14 thousand teeth in its 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 common shark, are able to live in both salt and fresh water, swimming into rivers. The depth of habitat of sharks is on average 2000 meters, 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 They eat crabs and other crustaceans.
The white shark preys on eared seals, elephant seals and cetacean mammals, while 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
The modern classification of these ancient fish, which existed hundreds of millions of years ago, identifies 8 main orders, forming about 450 species of sharks:
Carchariformes (gray, carcharidae) sharks(Carcharhiniformes)
This order unites 48 genera and 260 species. The following species are considered typical representatives of the order:
- Great hammerhead shark(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. The high dorsal fin is shaped like a sickle.
- Silk (Florida, widemouth) shark(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 that cover a shark's skin are so small that they create the effect of complete absence. The silky (Florida) shark reaches 2.5-3.5 meters in length. The maximum recorded weight is 346 kilograms.
- Tiger (leopard) shark ( Galeocerdo cuvier)
Lives off the coast of Japan, New Zealand, USA, Africa, India, Australia. The tiger shark is 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 (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. The surface of the body of the blunt-nosed shark is painted gray, the belly is white. The maximum recorded body length is 4 meters.
- Blue shark or blue shark (big shark or great blue shark) (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. The great blue shark 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.
Heterodontoid (bull, horned) sharks(Heterodontiformes )
The order includes one fossil and one modern genus, in which the following species can be distinguished:
- Zebra bull (Chinese bull, narrow-striped bull, narrow-striped horned) shark (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(Heterodontus galeatus)
A rare species that lives off the coast of Australia. Helmet skin bull sharks covered with large and rough skin 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 (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 (frill shark) (Chlamydoselachus anguineus)
This shark has the ability to bend its body and attack its prey like a snake. 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 (ashy sevengill shark, sevengill) (Heptranchias perlo)
It is slightly more than 1 meter long and, despite its 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(Lamniformes)
These are large fish, endowed with a body shaped like a torpedo. The order includes 7 genera:
- Gigantic (giant) sharks ( 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 primarily in the waters of the Atlantic, Pacific, North and Mediterranean seas.
- Fox sharks ( sea foxes) (Alopias)
They are very long top part caudal fin, equal to length torso. 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.
Fox sharks are common in waters North America and along the entire Pacific coast.
- Herrings (lumnaceae) sharks ( 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 warm waters world ocean.
- False sand sharks(Pseudocarcharias)
Pseudocarcharias kamoharai is the only species of the genus. 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(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. The maximum body length of this shark species is 3.7 m.
- Largemouth (pelagic) sharks(Megachasma)
Family Megachasma represented by a single and rare species Megachasmapelagios. Representatives of the largemouth shark species feed on plankton and are not dangerous to people. 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) (Mitsukurinidae)
They represent 1 species, which received the popular nickname “goblin shark” for its long beak-shaped nose. 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(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(Pristiophoriformes )
The order includes the only family Saw-nosed sharks or saw-nosed 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 predatory fish are common 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 (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) (Squatina)
They are distinguished by a wide, flat body, resembling a stingray in appearance. Representatives of sea angels have a length of slightly more than 2 meters, are predominantly nocturnal, and during the day they sleep, buried in the mud. They live in all warm waters of the world's oceans.
Shark breeding
Sharks are distinguished by long duration puberty. Most females are capable of fertilization only at 10 years of age, and the whale shark becomes sexually mature at the age of 30-40 years.
Sharks are characterized by internal fertilization: some species lay eggs, others are ovoviviparous, and other species are viviparous. Incubation period depends on the species and lasts from several months to 2 years.
A clutch of oviparous fish contains from 2 to 12 eggs.
After fertilization, shark eggs are covered with a protein shell, which in turn is also covered with a horn-like shell. This allows them to be protected from various marine predators.
The hatched baby immediately begins to live and feed on its own.
In sharks living in captivity, cases of parthenogenesis have been recorded - fertilization without the participation of a male individual.
Baby ovoviviparous sharks, hatched in the womb, remain for some time in the oviducts and continue to develop, first eating unfertilized eggs, and when teeth grow, their weak brothers and sisters.
As a result, one, or less often two, of the strongest cubs are born. The body length of a newborn shark varies, for example, white sharks are born 155 cm long, while tiger sharks are only 51-76 cm long.
Shark attacks on people, or killer sharks
According to international data, the leading countries in the number of shark attacks are the USA, Australia, Brazil, South Africa and New Zealand. However, according to unofficial statistics, the most dangerous countries are African countries. Here, the largest and most dangerous shark populations live in the areas of Mozambique, Tanzania and Ghana. It is worth noting that shark attacks on people occur mainly in ocean waters rather than in continental seas.
Throughout the history of its existence, people consider the shark to be a fiend of hell, a killer with the habits of a maniac and universal evil. There are a lot of stories about killer sharks around the world.
The danger that sharks supposedly pose to people has been greatly exaggerated thanks to science fiction books and sensational horror films. Only 4 species of sharks commit unprovoked attacks on people: white, tiger, tiptoe and bull sharks. The most common misconception is that sharks love human meat. In reality, having grabbed a piece, the shark will most likely spit it out, not finding anything in such food that satisfies its need to replenish energy reserves.
- Despite (or thanks to) their notoriety, sharks are considered one of the most curious fish, arousing the interest of scientists, divers, and many people far from the ocean world.
- In Chinese culture, sharks, or rather their parts, play a special role. Shark fin soup is a recognized delicacy and is offered to the most honored guests, and dried shark fins are considered an aphrodisiac.
- Japanese culture portrays sharks as terrible monsters that carry away the souls of sinners.
- The prevailing belief that shark cartilage is a panacea for cancer has no scientific evidence. Moreover, scientists have dispelled the myth that sharks are immune to cancer: many fish were found to have malignant tumors different systems and organs.
- Despite the fact that shark meat tends to accumulate mercury, this does not stop many; it is still used as a delicacy to this day.
- Strong and durable shark skin is used in the haberdashery industry and is also used to make abrasives.
- For centuries, sharks have been exterminated in the most irrational and blasphemous manner for the sake of their fins, which make up only 4% of their body weight. And the carcasses are left to rot on the ground or thrown into the ocean.
- The shark is a fish that plays an invaluable role in the ocean ecosystem, but a third of shark species are on the verge of extinction only due to human fault.
Fear and curiosity – these are the feelings the creators of the blockbuster “Jaws” hoped to evoke in viewers, but the effect exceeded all expectations. And we're not talking about Oscars and record box office receipts. The great white shark, presented in the film as a monster greedy for human flesh, began to be caught and exterminated without hesitation.
However, ichthyologists will say that in most cases, attacks by white sharks on humans are the result of incorrect identification of a swimming object. When viewed from the depths, a diver or surfer can easily pass for a pinniped or a turtle, and in general, great white sharks, due to their curiosity, try everything by the skin of their teeth.
Today, about 3.5 thousand individuals of this ancient predator live in the world's oceans, which is undoubtedly dangerous and therefore not well studied. But like any animal with a sinister reputation, the great white shark will always be of interest, especially to thrill-seekers.
It was previously believed that white sharks descended from megalodon - giant fish, up to 30 m long and weighing almost 50 tons, extinct 3 million years ago. But modern studies of the remains of the superpredator have made it possible to establish that megalodons belong to the family Otodontidae, and white sharks belong to the family of herring sharks, so the number of supporters of this version has greatly decreased.
Today, scientists consider Isurus hastalis, one of the extinct species of mako shark, to be the recognized ancestor of the white shark. Both predators have almost the same tooth structure, only in the white shark, during evolution, serrations have formed along the edges of the teeth.
Taxonomy of the white shark
The white shark belongs to the class of cartilaginous fish (Chondrichthyes), which means that its skeleton does not have bones, but consists entirely of cartilaginous tissue. In addition to sharks, stingrays and chimeras have this feature.
The white shark is part of the order Lamniformes, which unites large species of sharks with a torpedo-shaped body.
The dense build, pointed snout and 5 gill slits made it possible to classify the white shark as a member of the family of herring or lamn sharks (Lamnidae). Its closest relatives are the mako shark, salmon shark and lamna.
The genus of white sharks (Carcharodon) includes 2 extinct and one modern species - the great white shark ( Carcharodon carcharias), also called carcharodon or, due to its sad fame, man-eating shark.
Appearance of a great white shark
This is a stocky fish with a dense body, elongated in the shape of a torpedo. The head of the predator is very large, conical, with a pointed muzzle and mouth, curved into a parabola. On the sides of the head, closer to the pectoral fin, there are 5 huge gill slits that provide water respiration.
The pectoral fins are large, elongated in the shape of a sickle. The first dorsal fin is high, triangular in shape, growing slightly further than the base of the pectoral fins. Sometimes its top is rounded. The second dorsal fin is very small, as is the anal fin. On the pelvic fin of males there is an elongated element - a copulatory outgrowth.
The tail fin blades of the white shark are of the same width, which is typical of other herring sharks, which are capable of developing decent speed before attacking.
The name “white” shark does not quite accurately convey the coloration of the predator. Its upper part and sides are often gray, sometimes brownish or with a blue tint. There are dark, almost black specimens. But the belly of a white shark is dirty white.
Newborn sharks and adult individuals are completely identical in appearance, but differ only in size.
How much does a white shark weigh?
The maximum possible size and weight of Carcharodon still causes heated debate in scientific circles. In the authoritative encyclopedia of past years, “Animal Life,” 1971, the greatest height of a measured white shark is called 11 m, without indicating weight. However, the opinion of modern scientists on this matter is less optimistic. Ichthyologists believe that, given an ideal habitat, a white shark can grow to a maximum of 6.8 m in length.
A number of scientific sources claim that the largest white shark was caught off the coast of Cuba in 1945. Its length was 6.4 m and its estimated weight was 3,324 kg. The measurements were based on a photo of a white shark, so some experts believe that the real size of the fish is overestimated by at least 1 meter.
In 1988, a white shark was caught off the Canadian coast, which was measured and weighed. It was a female, 6.1 m long with a body weight of about 1,900 kg. This specimen is considered so far the only one whose dimensions and weight have been reliably confirmed.
Interesting fact: if you compare the weight of a great white shark with large representatives of other families, then its mass with the same length will be almost 2 times greater!
On average, adult individuals weigh from 680 to 1,100 kg. Females are heavier and larger than males, their length is 4.6-4.9 m, males grow from 3.4 to 4 m.
Nevertheless, what excites minds is not so much the impressive dimensions of the great white shark, but its deadly mouth. After all, larger predators live in the depths of the sea, for example, representatives of the family of giant sharks, and the teeth of the white shark are unique in their own way.
How many teeth does a white shark have?
This predator has the largest teeth of all fish existing today, their length is about 5 cm. Triangular-shaped teeth with rough jagged edges are arranged in several rows and are constantly renewed. The number of rows depends on the age of the fish, there are from 3 to 7. The upper jaws bear larger teeth, on the lower jaw the teeth are smaller but sharper.
Each row can contain from 30 to 40 teeth, i.e. total number There are more than 300 teeth in the mouth of a great white shark.
The teeth of the first, working row quickly wear out and, to replace the lost ones, fully formed new teeth rise from the gums and move forward. This “conveyor” is ensured by mobility in the gums and short tooth roots.
Today, thrill-seekers don't have to watch thrillers about sharks. An extreme type of ecotourism is extremely popular - cage diving, when a person, protected only by metal bars, sees the deadly jaws of the famous predator at arm's length. Entertainment costs everyone 50-150 euros. Dangerous attractions await their customers in places with the largest concentrations of representatives of the species.
Where are white sharks found?
Despite the obvious trend towards reduction in the species, white sharks continue to inhabit all oceans except the Arctic. The most numerous populations are found off the coast of South Africa, the American state of California, the Mexican state of Baja California, Australia and New Zealand. This is where they come from best photos white shark, chilling its realism.
Most carcharodon prefer coastal waters of the temperate zone with temperatures from 12 to 24 ° C and stay almost below the surface of the water. However, large specimens thrive in tropical waters, cold seas, the open ocean, and also at considerable depth. According to documented data, a great white shark was once caught at a depth of 1,280 m using industrial bottom tools.
Before the invention of radio beacons, it was believed that long journeys were characteristic only of male white sharks, while females stuck to their native shores all their lives. However, the ability to track the movements of fish using modern equipment has proven the fact of long migrations by individuals of both sexes.
For what purpose great white sharks travel enormous distances remains a mystery. For example, it took one individual 9 months to travel 20 thousand km from the coast of South Africa to Australia and back. Perhaps long migrations are associated with reproduction or seasonal fluctuations in the food supply in different parts of the range.
What do white sharks eat?
Their diet is extremely varied, but despite their reputation for eating everything, white sharks feed primarily on fish, crabs, small marine animals, cephalopods and bivalves. Among the fish found in the stomachs of caught specimens are herring, sardines, stingrays and tuna. Dolphins, porpoises, sea beavers, sea lions and seals are often the prey of predators.
The undigested remains in the stomachs of white sharks once again confirm how aggressive these predators are towards other marine life. Their victims include beaked whales, sharp-snouted crocodiles, northern elephant seals, sunfish and different kinds sharks: dusky dogfish, Australian nurse shark, great blue shark, fox and dogfish. However, such a menu is not typical for most white sharks and is rather the exception.
White sharks will not refuse carrion and happily eat the carcasses of dead cetaceans. Various inedible objects are often found in the stomachs of predators, for example, pieces of plastic, wood and whole glass bottles.
Sometimes great white sharks practice uncharacteristic cannibalism. For example, in the waters of Australia, before the eyes of observers, a 6-meter white shark bit its 3-meter relative in half.
If the hunt is successful, predators eat for future use. Thanks to its slow metabolism, a white shark weighing about a ton only needs 30 kg of whale blubber for 1.5 months. However, these are purely theoretical calculations, and in practice, predators eat much more, while demonstrating hunting skills honed over millions of years of evolution.
White shark hunting methods
Carcharodons live and hunt alone, but sometimes exhibit social behavior. For example, in the coastal waters of Cape Town, a group of 2-6 individuals is regularly spotted, which behave quite peacefully in the flock.
Observations carried out in South African waters have proven that there are various kinds of hierarchies within such groups. Females dominate over males, large individuals over smaller ones. At the meeting, representatives different groups and loners quickly determine the social position of each other and the alpha leader. Conflicts are usually resolved with warning bites and in most cases end there. However, white sharks always separate before hunting.
Unlike their relatives, white sharks often stick their heads out of the water, catching odors wafting through the air. This usually happens when patrolling archipelagos, where pinnipeds set up rookeries.
When the animals are in the water, the white shark begins the hunt. It swims towards the victim just under the surface of the water and makes a sharp throw, sometimes jumping half or completely out of the water. Seals or fur seals are grabbed from below across the body, large individuals are dragged to the depths and drowned, then torn into pieces and eaten. Small ones are swallowed whole.
In fog and at dawn, the chances of a white shark attacking the first time are 50/50. If the attempt is unsuccessful, the predator pursues the prey, reaching speeds of up to 40 km/h.
Northern elephant seals, which are found in abundance off the coast of California, are bitten from behind by white sharks, immobilizing them. Then they wait patiently for the victim to bleed out and stop resisting.
Dolphins are never approached from the front, excluding the possibility of detecting danger using echolocation.
If you don't try, you won't know. According to this principle, great white sharks determine the edibility of any object, be it a buoy or a person. According to statistics, between 1990 and 2011 there were 139 white shark attacks on humans, of which only 29 were fatal.
Even after an attack, carcharodons do not intentionally pursue people; the victims are single swimmers who die from painful shock. When there is a partner, the wounded man can be saved by driving away the predator and leaving the danger zone together.
Only newly born sharks hunt on their own and do not pose a danger to humans or large animals.
Reproduction of white sharks
Reproductive maturity of white sharks occurs late, when the fish reach their maximum size. Females mature at the age of 33 years, males are ready to breed at 26 years.
These predators do not survive in captivity, so research on them mating behavior and reproduction contain extremely scanty information.
Great white sharks are ovoviviparous fish. This means that fertilized eggs remain in the mother's oviducts. They hatch into embryos that feed on the eggs produced by the ovaries. A pregnant female carries on average 5-10 embryos, but theoretically a litter can contain from 2 to 14 cubs. During the early and intermediate stages, the hatchlings' bellies are very distended and filled with yolk, and when egg production stops, the fetus digests the nutrient reserves.
The exact timing of gestation in white sharks is unknown, but scientists believe that pregnancy lasts more than 12 months. The baby sharks are born fully developed, 1.2 to 1.5 m long, and ready to live independently.
How long does a white shark live?
The average lifespan of a great white shark is estimated at 70 years. Studies based on the study of vertebral growth have made it possible to determine the age of the oldest white shark. It turned out to be a 73-year-old male. However, not everyone manages to live to an old age.
Previously, scientists believed that the predator at the head of the food chain did not have natural enemies. But at the end of the last century, reports appeared of attacks on white sharks by killer whales, even larger and more bloodthirsty predators.
Another enemy of the white shark is the saltwater crocodile, which is capable of turning over a large fish and easily tearing its throat or belly.
Water pollution, accidental capture and poaching also reduce the already low numbers of the species. The price of a tooth on the black market is $600-800, and the cost of great white shark jaws reaches $20-50 thousand.
Today, predators are protected by law in many countries, for example, Australia, South Africa, the American states of Florida and California. By the way, Peter Benchley, the author of the famous novel “Jaws,” clearly did not expect the negative consequences of the sensational film adaptation. Therefore, the writer devoted the last 10 years of his life to studying the ocean ecosystem and actively advocated for great white sharks.
To date, not everything is known about sharks. Nevertheless, they arouse constant interest among people. More than one encyclopedia has been written about them. Not all species are dangerous to humans. They themselves suffer greatly because of people. Every year, up to 100 million individuals die due to fishing.
Who are sharks? They first appeared 450 million years ago. Since that time, these creatures have hardly changed. A shark is a fish that lived in the oceans long before dinosaurs.
There are about 450 species of sharks on the planet. These cartilaginous fish differ greatly from each other. The largest of them reaches a length of 20 m, while the length of the smallest is only 17 cm. Some of these predators, inhabitants of the depths, are able to glow with the help of special organs, luring prey.
How many years do sharks live? The answer to this question will be individual for each specific species. Polars are true long-livers. The lifespan of a shark of this species is more than 100 years. The life of a whale lasts more than 70 years. How long do these predators live on average? Most species have a lifespan ranging from 20 to 30 years.
The life of sharks is subject to a complex hierarchy that operates not only within one species, but also between representatives of different species. A significant number of species of these fish coexist with each other in large groups.
They swim at low speed most of the time. average speed Sharks range from 8 to 9 km/h. During a throw at a potential victim, they are capable of noticeably accelerating. The mako shark is considered the fastest. It is capable of reaching speeds of up to 50 km/h.
Anatomical data
Different types of sharks differ from each other in appearance. The sizes of these animals can vary greatly. What do sharks look like? Fish have a streamlined body shape, a specially shaped caudal fin, as well as two dorsal fins, an anal fin, paired abdominal and pectoral fins, and many teeth growing in several rows. The closest relatives of these creatures are stingrays.
The structure of a shark is different from that of other fish. These predators belong to cartilaginous fish. The name refers to one feature of shark anatomy. Their skeleton consists not of bones, but of cartilage.
The scales of the predator are designed in such a way that the tips of the scales protrude outward from the skin. They fit very tightly to each other, due to which the shark’s skin can appear either smooth if you run your hand in the direction from head to tail, or hard, rough, resembling sandpaper, if you stroke the sea predator in the opposite direction.
The teeth of these predators grow in several rows, their structure varies among different types and depends on what the fish eats. If for some reason the shark loses a tooth, the one in the previous row will take its place. In the very last row, after a while a new one will grow. As long as this predator lives, its teeth grow. The structure of the dental apparatus can reveal a lot about sharks.
Physiology
How do sharks breathe? A shark is a fish, and its respiration occurs in the same way as in other chordates. For this purpose, a special organ is used - gills. A shark's gill sacs open inward into the throat and outward at the sides of the head. There can be from 5 to 7 pairs of gill slits. Cartilaginous fish use gills only for breathing.
Most of these marine predators are cold-blooded animals. Only a few species are classified as partially warm-blooded. These shark species have thermoregulation that is different from others. They are able to maintain a body temperature 9-13°C warmer than the surrounding water. However, such a temperature difference does not apply to the entire body of the predator. Near the gills and heart the temperature will be equal to the ambient temperature.
Since sharks do not have a swim bladder, they must constantly be on the move. The need to constantly swim is due to the fact that most of these fish are not able to pump water through their gills on their own. Shark hunters use this. If you pull a shark down by its tail for a while, no water will flow into its gills. In this case, the predator may drown. However, there are exceptions to this rule. One of them is the nurse shark, which is capable of maintaining work respiratory system lying on the bottom.
How does a shark compensate for negative buoyancy? Compensation occurs by reducing body weight. This is helped by the cartilaginous skeleton, which is much lighter than the bone one, as well as the accumulation of carbon in the liver. To make swimming easier, the skin is covered with a thin film of fat. Some predators create positive buoyancy in a different way. They swallow air, creating a makeshift swim bladder from their stomach.
Food and hunting
What do sharks eat? The answer to this question will be different for different species of marine predators. Sharks are all carnivores, but their food preferences differ. Because these marine animals expend a lot of energy by constantly moving, they need to consume large amounts of fatty foods.
Most species do not attack humans. Only rare predators pose a danger.
The tiger shark, which feeds on everything that comes its way, including inedible objects, has earned the title of marine scavenger.
The largest shark, the whale shark, eats plankton. During feeding, it swims very slowly, developing a speed of no more than 1 m/s. The teeth of this shark species are not designed for grasping flesh. They are needed to hold plankton in the mouth. This type of shark is safe for humans. In addition to the whale shark, there are 2 more species of sharks that feed on plankton.
The great white shark's main diet consists of fish, pinnipeds, dolphins and porpoises. In addition, this predator can also eat carrion. Man is not the usual food of creatures. They attack people by mistake.
The main product in the diet of many sharks is fish. Cases of cannibalism are common. For this reason, cubs often live away from adults.
How do these creatures get their food? The answer to this question depends on the type of food of a particular species. The largest creatures feed on zooplankton, which they catch in their wide-open mouths, swimming through concentrations of krill at low speeds. Some believe that these giants are sharks without teeth. They have teeth, but they are not intended for tearing meat out of the victim's body.
Small-sized creatures hunt schooling fish.
Larger species hunt prey large sizes. They often lie in wait for prey, swimming around it in circles, after which, waiting for the right moment, they make a sharp jerk, attacking the victim. At the moment of throwing, this fish develops a speed significantly higher than usual. Such throws take a lot of energy and strength. At what speed are these throws made? From 19 to 50 km/h, depending on the type.
They can hunt either alone or in packs.
Habitat
Where do sharks live? The habitat depends on the species. In addition, some migrate.
The habitat of most of these fish is sea water. There is only one species that is found in the fresh water of Lake Nicaragua.
Most small species prefer to settle off the coast in warm seas. The larger ones swim in the open sea. Most often they can be found close to the surface. There are few people who prefer to live at depth. There are only a few species that are found in pitch darkness. Glowing sharks descend to a depth of more than 6 thousand meters during the day, and rise closer to the surface at night. Little is known about sharks of the deep. The choice of place where a shark lives depends on what food it prefers, size, and habits.
These fish can be found in most seas. In addition, sometimes they swim into river mouths, rising quite high upstream.
Reproduction
How do sharks reproduce? Despite the fact that a shark is a fish, it does not spawn. According to the type of reproduction, they can be divided into 3 types: viviparous, ovoviviparous and oviparous. These fish are characterized by internal fertilization.
Viviparous women develop several embryos. In some species, babies eat each other while still in the womb. Because of this reproductive feature, sharks sometimes have 2 queens.
Viviparity differs from ovoviviparity in that in the first case, a placenta is produced in the mother’s body, which ensures the metabolism between the mother’s body and the embryos. In the case of ovoviviparity, such metabolism does not occur. In this case, the young hatch from eggs in the female's body and are then born. All nutrients they are obtained from the yolk.
Oviparous birds lay 1 to 12 eggs on average. The only one that lays much more is the polar one. She lays up to 500 eggs at a time.
How long does pregnancy last? The answer to this question depends on the species. The whale bears its offspring for more than 2 years. Pregnancy of the frilled one lasts 3.5 years. The nurse shark carries embryos for 2 years, after which 1 baby is born from each of its uteruses.
Most of these fish lack maternal instinct. A mother can eat babies that she herself has recently given birth to. In the tiger predator, nature dulls hunger before giving birth so that the young have time to escape. Some time after the female gives birth, the instinct is restored. Therefore, young animals live separately from adults and are found mainly in shallow water. Only a few species of these predatory fish care for their own children.
If there are no males, then the shark will switch from sexual reproduction to asexual reproduction. This often happens in captivity. In the wild, cases of this fish reproducing in this way have not been recorded.
Fishing victims
Every year in the world from 40 to 100 million of these creatures become victims of fishing. They are caught for their fins, which are considered a delicacy, skin from which bags, briefcases, suitcases, shoes are made, teeth, liver and cartilage. Some time ago, cartilage extract was considered an effective cure for cancer. Although the effectiveness of this drug has not been confirmed, shark cartilage is considered a source of vitamins. The same applies to the liver. Teeth are used as souvenirs.
The most valuable part is the fins. Often these fish are caught just for their sake. After cutting off the fins, the fishermen throw the carcass overboard. At this point the shark is often still alive. A predator left without fins has no chance of survival. She cannot move and hunt on her own, since catching food requires speed, and will become easy prey for another predator or die from suffocation.
IN last years in many countries around the world it has been banned to catch these fish just for their fins. Fishermen must provide the entire carcass before cutting off the fins.
Monsters of the past
The giant megalodon is considered the largest shark to ever exist. The classification of megalodon is subject to much debate. On this moment This extinct underwater giant is the largest fish of all time.
Megalodon became extinct more than 2.5 million years ago. Only numerous remains have survived to this day. This huge fish was the owner of a terrifying dental apparatus. Reaching a length of up to one and a half tens of centimeters, jagged along the edges, its teeth grew in 5 rows. No animal on the planet had larger teeth. The giant jaw of sharks from the distant past exceeds human height. Currently, they are very expensive and are sold at auctions.
What do the sharks of the past look like? It is believed that megalodon was similar to a modern great white, but larger. Not a single fish existing in our time has such a size.
At the moment, not everything is known about ancient sharks. Some researchers suggest that megalodon is not actually extinct, but this has not yet been proven.
Megalolamna, which is now extinct, is also considered the closest relative of Megalodon. Little is known about sharks of this species.