Greenland polar shark - the largest representative of catranoids, belonging to the genus Somniosidae. Refers to cartilaginous fish, which are not yet widely studied.
Habitats
This is the coldest shark of all members of the family, preferring water temperatures ranging from 1 to 12 °C. The area of \u200b\u200bselahia covers the North Atlantic Ocean, the Arctic Ocean and includes the Scandinavian countries, the USA, Canada, Russia, Iceland and Germany. The Greenland polar shark (somniosus microcephalus) lives in a vast vertical range - from the continental and insular 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. She makes daily and seasonal migrations, determined by the movement of plankton and small animals that make up her diet.
Appearance
The Greenland polar shark is in sixth place in size after the white, reaching 8 meters in length and weighing up to two tons. But the average size of individuals is 4 m, and the weight is 800 kg.
Her body hasstreamlined torpedo-like shape. The head is small in size relative to the entire carcass. The predator's mouth is on the bottom. The jaws are wide and clumsy. The lower one is studded with blunt square teeth, while the upper one is studded with rare sharp ones. The height of both does not exceed 7 mm. Caudal fin heterocercal type, dorsal - rounded and small in size.
The body of the selahia has a color from brown to almost black, sometimes with a greenish tinge. There are dark purple spots all over the body. Shark eyes are small, green, without a protective membrane. They are able to glow in the dark, which is explained by the accumulation of bioluminescent copepods that parasitize the area around the eyes of this giant.
Building features
The Greenland shark has a large fatty liver, which exceeds 20% of its total body weight. This body acts as an additional float.
Shark tissues are highly saturated with ammonia and trimethylamine oxide. Such compounds prevent blood from freezing, support the efficiency of proteins and the normal course of biological processes in the conditions of the north. Both substances are toxins, so shark meat not only tastes disgusting, but can also lead to poisoning - under the action of gastric juice, trimethylamine oxide turns 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 impressive in size and slow. Its speed of movement is surprisingly low - no more than one kilometer per hour. This is explained by the fact that, living in cold waters, most of the energy of selachia is forced to spend on heating its own body. The Greenland polar shark is a long-liver among representatives of the animal world. As established, its life expectancy is up to 500 years.
Food
The large size, low speed of movement and the small mouth of selachia significantly affect what the Greenland shark eats. She is too slow, cautious and even to some extent cowardly, therefore she most often watches over sleeping, sick or weak seals and thus hunts them. The main diet includes organic waste, carrion and small animals such as cod, flounder, sea bass, octopus, crab, squid, stingray. In the stomachs of these predators, jellyfish, algae, the remains of reindeer and polar bears were found. The smell of rotting meat attracts bowhead sharks, so they can often be found near fishing boats.
Reproduction
This period falls at the end of spring. Selahia belongs to ovoviviparous animals - she bears 8 cm eggs without a cornea inside herself. For one litter, up to a dozen cubs with a size of at least 90 cm are born in a Greenland shark. Females acquire reproductive ability upon reaching the age of 150 years, their length by this moment is 4.5 mit is smaller than males - about 3 m.
Human Interaction
The polar (or Greenland) shark belongs to the top predators. No one hunts her, the only enemy is man. These sharks are targeted for their livers, which humans use to make vitamin-rich technical fat. The Greenland Shark has been designated Near Threatened. This species is under close scrutiny by conservation organizations as shark populations are declining every year, in part due to slow reproduction.
As mentioned above, raw selahia meat is highly toxic due to its high urea and TMAO content. But the natives of the north have learned how to process it for eating and feeding pets - soaking and boiling repeatedly can neutralize toxins. The Icelanders, being the descendants of the glorious Vikings, prepare the traditional hakarl dish from it. Today sharks are also fished in some other countries. She is quite phlegmatic and completely non-aggressive. Surprisingly, such a giant, caught in a net, behaves very quietly. Some fishermen consider these marine creatures to be pests - for damaging gear and exterminating fish.
Cases of polar shark attacks on humans are extremely rare, because in the cold places where they live, the probability of meeting is very small. However, there is a known case when the Greenland polar shark became the reason that a group of divers had to rise to the surface of the water.
Interesting facts
Today, according to 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. She does not develop calcium carbonate deposits in her ears, which determine the age of most fish; selachia's vertebrae are as soft as paraffin, which makes it impossible to determine life expectancy by the growth of vertebral rings.
The age of polar sharks was determined by the proteins in the center of the lens of the eye. It grows throughout life, and its proteins are formed at the stage of embryonic development. Radiocarbon analysis 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 method of research, it has been established that polar sharks can live up to 500 years. Such longevity is explained by the fact that all life processes in cold water are slower than in heat-loving representatives of this family.
