Last year, scientists managed to discover a Greenland shark, whose age exceeds 400 years - a record life expectancy among vertebrates! Of course, there is an explanation for this fact - the shark lives at great depths in the icy waters of the ocean, which significantly slows down its metabolism.
An international team of researchers conducted radiocarbon dating of the lens of the eyes of several Greenland sharks and found that their average lifespan is about 300 years, with scientists estimating the age of the oldest individual at almost four centuries or even more. Thus, Greenland sharks turned out to be the longest-living vertebrates. The study was published in the journal Science.
Greenland sharks are widespread in the north Atlantic Ocean and are found both at the surface and at depths of more than two thousand meters. The average body length of an adult typically reaches four to five meters, and the weight can reach up to 400 kilograms, making it the largest fish in Arctic waters. Due to the inaccessibility of their habitat, these animals have been little studied, but their slow annual growth (from 0.5 to 1 centimeter in length) suggested that they lived extremely long.
To determine the lifespan of Greenland sharks, researchers radiocarbon dated the nucleus of the eye lens of 28 female sharks. The fact is that the nucleus of the lens grows throughout the life of the animal, and the older the individual, the more layers of lens fibers the nucleus of its lens has. By removing these layers, scientists can get to the embryonic nucleus of the lens, which is formed in a shark before birth, and determine the age of the fish based on the carbon-14 isotope content in it.
The scientists' analysis showed that the average life expectancy of Greenland sharks reaches at least 272 years, which makes them the longest-living record among vertebrates. Researchers estimated the age of the largest shark (502 centimeters long) at 392 ± 120 years, and individuals whose size was less than 300 centimeters turned out to be younger than a hundred years. The authors also state that Greenland sharks reach sexual maturity at approximately 150 years of age.
Thus, in terms of life expectancy, sharks were second only to the mollusks Arctica islandica, which live up to 507 years, and became the first among vertebrates, overtaking the previous record holder - the bowhead whale, some individuals of which live up to 211 years. Scientists cannot explain why Greenland polar sharks live so long, but they suggest that this is due to the low water temperatures in their habitats and, as a result, the slow metabolism of sharks.
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 depths 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 autumn. 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.
TMAO, found in the tissues of Greenland sharks, helps stabilize enzymes and structural proteins that would otherwise not function properly due to low temperature 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 ambient pressure is about 220 atmospheres or 220 kilograms per square centimeter. It is not surprising that the concentration of the protective substance TMAO in the tissues of Greenland sharks 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. The traditional Icelandic dish hakarl is prepared from the meat of polar sharks through long-term processing. 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.
Greenland polar shark, or small-headed polar shark, or Atlantic polar shark (lat. Somniosus microcephalus) - belongs to the family of straight-mouthed sharks.
If for most sharks the acceptable ocean water temperature starts at +18 degrees, then polar sharks have chosen truly cold waters where the temperature does not exceed -2 to +7 degrees. But how is this even possible - after all, sharks are extremely thermophilic, even those whose bodies are capable of raising the temperature above the temperature of the surrounding water?
First, about the Arctic sharks themselves. The most famous representative among the genus Somniosidae is the Atlantic (aka Greenland, aka small-headed) polar shark (Somniosus microcephalus). Its permanent habitat is the northwestern coast of Europe and the coast of Greenland; sometimes it can be found off the northern coast of Russia.
Externally, this fish is very similar to a torpedo, and its dorsal fins, which have become the hallmark of sharks, are small in size. It is these sharks that live longer than all others - about 100-200 years! The polar shark has become a long-liver due to the slow progression of all life processes in its body. It grows very slowly: an individual of such a shark was kept in a scientific institute, where it was studied for a long time - in 16 years the predator grew only 8 cm.
The predator has the largest liver among all other sharks, it reaches 20% of its total weight - because of this organ, about 30 thousand individuals were annually caught on polar sharks for centuries, and industrial fat was melted from the liver. Fishing for this fish is not interesting for sports fishermen - there is practically no struggle; after the predator is brought to the surface of the ocean, it rises into the boat just as if it were a log.
The polar shark does not swim away from Arctic waters; in summer it stays at a depth of 500-2000 meters, and winters at the surface of the ocean - the water temperature here is higher.
It feeds on any local living creatures, be it fish or pinnipeds, and also attacks unwary animals caught in the water. For a long time, this shark was considered a carrion eater: it is always slow, so this fish is often called sleepy - where can it keep up with its prey! However, in 2008, Keith Kovacs, an ichthyologist at the Norwegian Polar Institute in Troms, discovered the bones of a polar bear, eaten “fresh” by the fish, in the stomach of a captured polar shark. This discovery was the subject of a serious debate among scientists - could a polar shark attack and kill a polar bear?
Theoretically, an adult predator is quite capable of drowning a bear, because her height and weight are twice as large - 6 meters and 1,000 kg, respectively. And yet, according to scientist Vince Gallucci of the University of Washington and Jeffrey Gallant, a Canadian marine predator researcher, the Arctic shark will not take such a risk - an attack on a large predator with impressive fangs and claws.
She is quite content with easier prey, hunting for which does not involve the risk of injury. Gallucci believes that the bear drowned himself, and the shark discovered his body and feasted. On the other hand, in the legends of the indigenous inhabitants of Greenland - the Inuit Eskimos - there are stories about arctic sharks attacking kayaks and caribou who dared to come close to ice holes.
The polar shark ranks sixth in size among other species of predators.
The size of animals at birth is approximately 38 cm, maturity is reached when males reach a length of 3-3.5 m, females - 4-5 m. The maximum length of a shark is 8m. Like other sharks, this species is viviparous.
In terms of aggressiveness, this species is not far from the whale shark.
The teeth of this predator are small - their length does not exceed 7 mm, the upper ones are needle-shaped, the lower ones are strongly curved. The mouth itself is small and cannot open wide.
There is no unanimous opinion among ichthyologists about the reproduction of polar sharks. Some sources indicate that this fish is viviparous, with a litter of up to 10 sharks about 1 meter long.
According to other sources, the polar shark reproduces in the spring, laying oval-shaped eggs in quantities of up to 500 pieces at depth. These eggs are quite large (up to 8 cm in diameter) and do not have a protective cornea. The eggs hatch into polar shark fry. Time will apparently tell which scientist is right.
But the most dangerous enemy for the polar shark is man. It is he who can threaten the extinction of any species of living beings on the planet, as often happens.
And finally, how does the polar shark survive in the icy waters of the Arctic?
And she succeeds in this because among the organs of her body there are no kidneys or urine-excreting pathways - the removal of ammonia and urea occurs through the skin of the predator. Therefore, the muscle tissue of a shark contains large quantities of nitrogen trimethylamine, which is also a “natural antifreeze” (osmolyte), which prevents the predator’s body from freezing even at subzero temperatures.
It is known that trimethylamine, contained in fresh polar shark meat, causes an effect similar to intoxication in dogs that eat it - the dogs cannot rise to their paws for some time. By the way, the Eskimos of Greenland call a drunk person a “sick shark.” Most likely, it is precisely because of the nitrogen content of trimethylamine in the body that the polar shark is so slow.
The meat of these sharks can be eaten if it is kept in the sun for several months, placed in a natural glacier for about six months, or boiled in repeatedly changed water. The Icelandic national dish, hakarl, is prepared from shark meat.
Scientific classification
Kingdom: Animals
Type: Chordates
Class: Cartilaginous fish
Squad: Katraniformes
Family: Somniosidae
Genus: Arctic sharks
View: Arctic shark (Somniosus microcephalus)
The shark family is very widespread and quite well studied.
Each of us knows that there are terrible predators such as the white shark or the tiger shark. But among sharks there are also absolutely amazing species, like the Greenland shark.
This species, which until recently no one had heard of, has not yet been so well studied, but it is unique. The fact is that the Greenland shark can live and roam the icy oceans of the planet for over a hundred years.
Description and lifestyle
The Greenland shark - Somniosus microcephalus, discovered off the northern coast of Europe, along the coast of Labrador and near the island, shocked researchers.
How could a typical tropical predator end up in these harsh, cold waters? From the first meeting, scientists did not leave Greenland sharks unattended, hoping to find out their secrets. However, there are still too many secrets.
The Greenland shark is a very large predator, on average up to 7 meters long and weighing a ton. Typically these sharks are about four meters long. Unlike most of its relatives, its dorsal fin is small, its sharp teeth do not even reach a centimeter in length, its color is close to coffee - instead of the usual gray - and it can swim in water at a temperature slightly below zero.
The polar shark is always leisurely. This predator feeds on a variety of fish and does not disdain crabs and jellyfish. There is also a very paradoxical fact in her biography: the shark’s favorite delicacy is fur seals. How does such a phlegmatic predator manage to overtake agile and fast cats? However, this is a fact, since whole pieces of meat from fur seals and sea lions were often found in the stomachs of polar sharks.
For all their slowness, sharks have an enormous appetite, given that large prey has been found in their stomachs more than once: a whole seal, a considerable amount of cod and salmon, a reindeer without horns and even a polar bear. Perhaps the latter became a victim during his long swim.
In 2016, a group of international researchers led by leading specialist at the University of Copenhagen, Julius Nielsen, found that the age of the shark caught off the coast of Greenland was more than 400 years. After more thorough research, the exact age was established as 512 years.
Greenland sharks live under the ice of the Arctic Ocean and its coastal seas at depths of up to 600 meters. These are the largest sharks in the world, they grow up to 20 meters and can live several hundred years. It is believed that they even eat polar bears.
Due to its cold habitat, the shark is a long-liver. Like a product in the refrigerator, it takes a long time to mature and becomes sexually mature at the age of about 140 years. Trimethylamine nitrogen, produced and accumulated in the muscles of the fish, allows it to live in such cold conditions.
For humans, a shark does not pose any particular danger, but according to Inuit legends, there have been cases when fish have capsized kayaks. Most likely, the predator simply confused them with prey. Greenland sharks were previously hunted for their large livers. Meat is not eaten without proper preparation. Very long and difficult.
Last year, scientists managed to discover a Greenland shark, whose age exceeds 400 years - a record life expectancy among vertebrates! Of course, there is an explanation for this fact - the shark lives at great depths in the icy waters of the ocean, which significantly slows down its metabolism.
An international team of researchers conducted radiocarbon dating of the lens of the eyes of several Greenland sharks and found that their average lifespan is about 300 years, with scientists estimating the age of the oldest individual at almost four centuries or even more. Thus, Greenland sharks turned out to be the longest-living vertebrates. The study was published in the journal Science.
Greenland sharks are widespread in the north Atlantic Ocean and are found both at the surface and at depths of more than two thousand meters. The average body length of an adult typically reaches four to five meters, and the weight can reach up to 400 kilograms, making it the largest fish in Arctic waters. Due to the inaccessibility of their habitat, these animals have been little studied, but their slow annual growth (from 0.5 to 1 centimeter in length) suggested that they lived extremely long.
To determine the lifespan of Greenland sharks, researchers radiocarbon dated the nucleus of the eye lens of 28 female sharks. The fact is that the nucleus of the lens grows throughout the life of the animal, and the older the individual, the more layers of lens fibers the nucleus of its lens has. By removing these layers, scientists can get to the embryonic nucleus of the lens, which is formed in a shark before birth, and determine the age of the fish based on the carbon-14 isotope content in it.
The scientists' analysis showed that the average life expectancy of Greenland sharks reaches at least 272 years, which makes them the longest-living record among vertebrates. Researchers estimated the age of the largest shark (502 centimeters long) at 392 ± 120 years, and individuals whose size was less than 300 centimeters turned out to be younger than a hundred years. The authors also state that Greenland sharks reach sexual maturity at approximately 150 years of age.
Thus, in terms of life expectancy, sharks were second only to the mollusks Arctica islandica, which live up to 507 years, and became the first among vertebrates, overtaking the previous record holder - the bowhead whale, some individuals of which live up to 211 years. Scientists cannot explain why Greenland polar sharks live so long, but they suggest that this is due to the low water temperatures in their habitats and, as a result, the slow metabolism of sharks.
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 depths 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 autumn. 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.
TMAO, found in the tissues of Greenland sharks, helps stabilize enzymes and structural proteins that would otherwise not function properly due to low temperature 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 ambient pressure is about 220 atmospheres or 220 kilograms per square centimeter. It is not surprising that the concentration of the protective substance TMAO in the tissues of Greenland sharks 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. The traditional Icelandic dish hakarl is prepared from the meat of polar sharks through long-term processing. 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 Greenland polar shark is the largest representative of the catraniformes, belonging to the genus Somniosidae. Refers to which have not yet been widely studied.
Habitats
This is the most cold-loving shark of all members of the family, preferring water temperatures in the range from 1 to 12 °C. Selachia's range covers the North Atlantic and includes the Scandinavian countries, USA, Canada, Russia, Iceland and Germany. The Greenland polar shark (somniosus microcephalus) lives in a wide vertical range - from the continental and island shelves to 2000 m or more. In summer it is most often found at a depth of 200-500 m, and in winter - closer to the surface. It makes daily and seasonal migrations, determined by the movement of plankton and small animals that make up its diet.
Appearance
The Greenland polar shark is the sixth largest shark after the white shark, reaching 8 meters in length and weighing up to two tons. But the average size of individuals is 4 m, and their weight is 800 kg.
Its body has a streamlined torpedo-like shape. The head is small in size relative to the entire carcass. The predator's mouth is on the lower part. The jaws are wide and clumsy. The lower one is dotted with blunt square teeth, and the upper one - with rare sharp ones. The height of both does not exceed 7 mm. The caudal fin is heterocercal type, the dorsal fins are round in shape and small in size.
Structural features
The Greenland shark has a large, fatty liver that makes up more than 20% of its entire body weight. This organ serves as an additional float.
Shark tissues are highly saturated with ammonia and trimethylamine oxide. Such compounds prevent blood from freezing, support the functioning of proteins and the normal course of biological processes in northern conditions. Both substances are toxins, so they not only have a disgusting taste, but can also lead to poisoning - under the influence of gastric juice, trimethylamine oxide is converted into trimethylamine, which causes an alcoholic effect. The shark does not have a bladder, so waste products are excreted through the skin.
These animals are distinguished by their impressive size and slowness. Its movement speed is surprisingly low - no more than one kilometer per hour. This is explained by the fact that, living in cold waters, the selakhia is forced to spend most of its energy on heating its own body. The Greenland polar shark is the longest-lived among the representatives of the animal world. It has been established that its life expectancy is up to 500 years.
Nutrition
The large size, low speed of movement and small mouth of the Selachia significantly influence what the Greenland Arctic shark feeds on. She is too slow, cautious and even cowardly to some extent, so she most often watches for sleeping, sick or weak seals and thus hunts them. The main diet includes organic waste, carrion and small animals such as cod, perch, octopus, crab, squid, stingray. In the stomachs of these predators, jellyfish, algae, and the remains of reindeer and polar bears were found. The smell of rotting meat attracts Greenland sharks, so they can often be found near fishing boats.
Reproduction
This period occurs at the end of spring. Selakhia is an ovoviviparous animal - it bears eggs 8 cm in size without a cornea inside itself. In one litter, the Greenland shark gives birth to up to a dozen cubs measuring at least 90 cm. Females acquire reproductive capacity upon reaching the age of 150 years, their length at this time is 4.5 m, for males it is less - about 3 m.
Human interaction
The Arctic (or Greenland) shark is a super predator. No one is hunting her, the only enemy is man. These sharks are hunted for their liver, which people use to obtain technical fat rich in vitamins. The Greenland shark has been classified as Near Threatened. This species is under close monitoring by environmental organizations, as the shark population decreases every year, partly due to slow reproduction.
As mentioned above, raw selachia meat is very poisonous due to its high urea and TMAO content. But the northern aborigines learned to process it for consumption and feeding domestic animals - soaking and repeated boiling helps neutralize toxins. Icelanders, being descendants of the glorious Vikings, prepare the traditional dish Hákarl from it. Shark fishing is also practiced in some other countries today. She is quite phlegmatic and completely non-aggressive. Surprisingly, such a giant, caught in a net, behaves very quietly. Some fishermen consider these marine inhabitants to be pests - for damaging gear and destroying fish.
Cases of polar shark attacks on humans are extremely rare, because in the cold places where they live, the likelihood of an encounter is very low. However, there is a known case when a Greenland polar shark became the reason that a group of divers had to rise to the surface of the water.
Today, based on the results of numerous studies, it is known that the Greenland shark is the oldest vertebrate in the world. However, to establish this fact, scientists had to make a lot of effort. The fact is that most of the methods used to determine the age of an animal are not applicable to the polar shark. It does not form layers of calcium carbonate in its ears, which are used to determine the age of most fish; Selachia's vertebrae are soft, like paraffin, which makes it impossible to determine life expectancy based on the growth of vertebral rings.
The age of polar sharks was determined by the proteins in the center of the eye lens. It grows throughout life, and its proteins are formed at the stage of embryonic development. made it possible to determine their lifetime by the content of the carbon-14 isotope, the surge of which occurred after the testing of atomic bombs. One of the sharks studied by specialists was 392 years old. Taking into account the error of the radiocarbon dating method, it has been established that polar sharks can live up to 500 years. This longevity is explained by the fact that all life processes in cold water are slower than in heat-loving representatives of this family.
