The Greenland shark is very slow, but it also lives incredibly long, this is one of the real wonders of nature: both the duration of its life and its adaptability to icy water are of interest. For a fish of this size, these features are unique. In addition, unlike its southern “relatives”, it is very calm and does not threaten people.
Origin of the species and description
Sharks are a superorder of predatory fish , their name in Latin is Selachii. The oldest of them, the hybodontids, appeared in the Upper Devonian period. The ancient selachians disappeared during the Permian extinction, opening the way for the active evolution of the remaining species and their transformation into modern sharks.
Their appearance dates back to the beginning of the Mesozoic and begins with the division into actual sharks and rays. During the Lower and Middle Jurassic periods, active evolution took place, then almost all modern orders were formed, including the catarrhoids, which include the Greenland shark.
Video: Greenland shark
Mostly sharks were attracted, and to this day they are attracted by warm seas, how some of them settled in cold seas and changed to live in them has not yet been reliably established, and also in what period this happened – this is one of the questions that occupies researchers .
The description of the Greenland shark was made in 1801 by Markus Bloch and Johann Schneider. Then they received the scientific name Squalus microcephalus – the first word means katran, the second is translated as “small head”.
Subsequently, they, along with some other species, were allocated to the Somniose family, while continuing to belong to the katraiformes order. Accordingly, the specific name was changed to Somniosus microcephalus.
Already in 2004, it was discovered that some of the sharks that were previously classified as Greenland sharks were actually a separate species – they were called Antarctic. As the name implies, they live in Antarctica – and only in it, while Greenlandic – only in the Arctic.
Interesting fact: The most remarkable feature of this shark is longevity. Of those individuals whose age has been clarified, the oldest — 512 years. This makes it the oldest living vertebrate. All members of this species, unless they die from injury or disease, are able to live to be several hundred years old.
Appearance and features
It has a torpedo shape , on her body, to a much lesser extent than on most sharks, fins are visually distinguished, since their size is relatively small. In general, they are relatively poorly developed, like the caudal peduncle, and therefore the Greenland shark does not differ in speed at all.
Also, the head does not stand out much due to the short and round snout. The gill slits are small compared to the size of the shark itself. The upper teeth are narrow, while the lower ones, on the contrary, are wide, in addition, they are flattened and beveled, in contrast to the symmetrical upper ones.
The average length of this shark is about 3-5 meters, and the weight is 300-500 kilograms. The Greenland shark grows very slowly, but also lives incredibly long – hundreds of years, and during this time the oldest individuals can reach 7 meters and weigh up to 1,500 kilograms.
The color of different individuals can vary greatly: the lightest ones have a grayish-cream skin, and the darkest ones are almost black. All transitional shades are also presented. The color depends on the habitat and nature of the shark's diet, and can change slowly. It is usually uniform, but sometimes there are dark or white spots on the back.
An interesting fact: Scientists explain the longevity of Greenland sharks primarily by the fact that they live in a cold environment – their metabolism is greatly slowed down in their body, and therefore tissues remain much longer. Studying these sharks may also provide a clue to slowing down human aging.
Where does the Greenland shark live?
They live exclusively in arctic, ice-bound seas – north of any other shark. This is explained simply: the Greenland shark loves the cold very much and, once in a warmer sea, quickly dies, since its body is adapted exclusively to cold water. The preferred water temperature for it is in the range from 0.5 to 12 ° C.
Mostly its habitat includes the seas of the Atlantic and Arctic Oceans, but not all – they primarily live off the coast of Canada, Greenland and in the northern European seas, but there are very few of them in those that wash Russia from the north.
- off the coast of the northeastern United States (Maine, Massachusetts);
- Saint Lawrence Bay;
- Labrador Sea;
- Baffin Sea;
- Greenland Sea;
- Bay of Biscay;
- North Sea;
- waters around Ireland and Iceland.
Most often they can be found on the shelf, near the coast of the mainland or islands, but sometimes they can swim far into the ocean waters, to a depth of up to 2,200 meters. But usually they do not descend to such extreme depths – in summer they swim several hundred meters below the surface.
In winter, they move closer to the coast, at this time they can be found in the surf zone or even at the mouth of the river, in shallow water. Changes in depth during the day have also been observed: several sharks from the population in the Baffin Sea, which were observed, descended to a depth of several hundred meters in the morning, and from noon they went up, and so every day.
What does the Greenland Shark eat?
It is not able to develop not only high, but even average speed: its limit is 2.7 km/h, which is slower than any other fish. And this is still fast for her – she cannot keep such a “high” speed for a long time, but usually develops 1-1.8 km/h. With such high-speed qualities, she cannot keep up with prey in the sea.
Such slowness is explained by the fact that her fins are rather short, and her mass is large, besides, due to a slow metabolism, her muscles also contract slowly: it takes her seven seconds to make one movement of her tail!
Nevertheless , the Greenland shark feeds on living creatures faster than itself – it is very difficult to catch it, and if we compare by weight how much prey the Greenland shark manages to catch and some faster one that lives in warm seas, the result will differ significantly, or even by orders of magnitude – naturally, not in favor of the Greenlandic one.
And yet, even a modest catch is enough for her, since her appetite is also orders of magnitude lower than that of faster sharks of the same weight – this is due to the same factor of slow metabolism.
The basis of the diet of the Greenland shark:
- marine mammals.
The situation is especially interesting with the latter: they are much faster, and therefore, while they are awake, the shark has no chance of catching them. Therefore, she lies in wait for them sleeping – and they sleep in the water so as not to become the prey of polar bears. Only in this way can the Greenland shark get close to them and eat meat, for example, a seal.
It can also eat carrion: it certainly cannot escape, unless it is carried away by a fast wave, behind which the Greenland shark will be unable to keep up. So, in the stomachs of the caught individuals, the remains of deer and bears were found, which the sharks obviously could not catch on their own.
If ordinary sharks flock to the smell of blood, then Greenland sharks are attracted by rotting meat, because of which they sometimes follow fishing boats in whole groups and devour the living creatures that are thrown from them.
Features of character and lifestyle
Due to their low metabolism, Greenland sharks do everything very slowly: they swim, turn, float and dive. Because of this, they have earned a reputation as a lazy fish, but in fact, for themselves, all these actions seem to be quite fast, and therefore it cannot be said that they are lazy.
They do not have good hearing, but they have an excellent sense of smell, on which they mainly rely in search of food – it is rather difficult to call it hunting. In these searches spend a significant part of the day. The rest of the time is devoted to rest, because they cannot waste a lot of energy.
They are credited with attacks on people, but in reality there is practically no aggression on their part: only cases are known when they followed ships or divers, while not showing overtly aggressive intentions.
Although Greenland sharks appear in Icelandic folklore as dragging and devouring people, but, judging by all modern observations, these are nothing more than metaphors, and in reality they do not pose a danger to humans.
Interesting fact: Researchers still do not have a consensus on whether the Greenland shark can be attributed to the number of organisms with negligible aging. They turned out to be a very long-lived species: their body does not become decrepit due to time, but they die either from injuries or from diseases. It has been proven that some other species of fish, turtles, molluscs, hydra are among such organisms.
Social structure and reproduction
Years for them go very differently – much more imperceptibly than for people, because all the processes in their body proceed very slowly. Therefore, they reach puberty by about the age of one and a half centuries: by that time, males grow to an average of 3 meters, and females reach one and a half times their size.
The time for reproduction comes in the summer, after fertilization, the female bears several hundred eggs, on average, 8-12 already fully developed sharks are born, already at birth reaching impressive sizes – about 90 centimeters. The female leaves them immediately after giving birth and does not care at all.
Newborns immediately have to look for food and fight off predators – in the first few years of life, most of them die, even though there are much fewer predators in northern waters than in warm southern ones. The main reason for this is their slowness, due to which they are almost defenseless – fortunately, at least their large size protects against many aggressors.
An interesting fact: Greenland sharks do not form otoliths in the inner ear, which used to make it difficult to determine their age – scientists have known for a long time that they are centenarians, but they could not establish exactly how long they live.
The problem was solved with the help of radiocarbon analysis of the lens: the formation of proteins in it occurs even before the birth of the shark, and they do not change throughout its life. And so it turned out that adults live for centuries.
Natural enemies of Greenland sharks
Adult sharks have few enemies: of the large predators in the cold seas, mainly killer whales are found. The researchers found that although other fish predominate on the killer whale menu, Greenland sharks can also be included in it. They are inferior to killer whales in size and speed, and practically nothing is able to oppose them.
Thus, they turn out to be easy prey, but how much their meat attracts killer whales has not been reliably established – because it is saturated with urea, and it is harmful for both humans and many animals. Of the other predators of the northern seas, no one threatens adult Greenland sharks.
Most of them die because of a person, even despite the absence of active fishing. There is an opinion among fishermen that they devour fish from gear and spoil them, therefore some of the fishermen, if they come across such prey, cut off its tail fin, and then throw it back into the sea – naturally, it dies.
Parasites annoy them, and more than others worm-like, penetrating into the eyes. They gradually eat the contents of the eyeball, due to which vision deteriorates, and sometimes the fish even goes blind. Luminous copepods can live around their eyes – their presence is indicated by a greenish luminescence.
Interesting fact: Greenland sharks survive in Arctic conditions thanks to trimethylamine oxide contained in body tissues, with the help of which proteins in the body can continue to function at temperatures below °C – without it, they would lose their stability. And the glycoproteins produced by these sharks serve as antifreeze.
Population and species status
Endangered species, they are not included, however, they cannot be called prosperous either – they have a status close to vulnerable. This is due to the relatively low population level, which is gradually falling even though the commercial value of this fish is low.
But still it is – first of all, the fat of their liver is valued. This organ is very large, its mass can reach 20% of the total body weight of the shark. Its raw meat is poisonous, causing food poisoning, convulsions, and in some cases death. But with long processing, you can make haukarl from it and eat it.
Because of the valuable liver and the ability to use meat, the Greenland shark was previously actively caught in Iceland and Greenland, because the choice there was not too wide. But in the last half century, fishing has been almost non-existent, and it comes mainly as bycatch.
Sport fishing, from which many sharks suffer, is also not practiced in relation to it: there is little interest in fishing because of its slowness and lethargy , it offers almost no resistance. Fishing for it is compared to fishing for a log, which, of course, has little excitement.
An interesting fact: The method of preparing haukarl is simple: shark meat cut into pieces must be folded into containers filled with gravel and having holes in the walls. For a long time – usually 6-12 weeks, they “rest”, and juices containing urea flow out of them.
After that, the meat is taken out, hung on hooks and left to dry outdoors for 8-18 weeks. Then cut off the crust – and you can eat. True, the taste is very specific, as is the smell – it is not surprising, given that this is rotten meat. Therefore, Greenland sharks almost ceased to be caught and eaten when alternatives appeared, although in some places haukarl continues to be cooked, and festivals dedicated to this dish are even held in Icelandic cities.
The Greenland shark is harmless and very interesting to study fish. It is all the more important to prevent a further decline in its population, because it is very important for the already poor Arctic fauna. Sharks grow slowly and breed poorly, and therefore it will be very difficult to restore their numbers after falling to critical values.