Greenland Shark

The International Union for the Conservation of Nature lists the Greenland shark as vulnerable to extinction.

The Greenland shark’s scientific name is Somniosus microcephalus, and its Latin name roughly translates into “sleepy little head.” This species has been described in scientific literature as “notably sluggish.”

Lumpish, with stunted pectoral fins that they use for ponderously slow swimming in cold and dark Arctic waters, they have blunt snouts and gaping mouths that give them an unfortunate, dull-witted appearance.

Shark Facts

There are around 450 known species of sharks, divided into eight separate orders. Each one has adapted to survive in a completely different environment: Some spend their lives thousands of feet under the sea, and others have made freshwater rivers their homes.

Sharks have been around for a really, really long time. For reference, the very first dinosaurs evolved 240 million years ago, and T-Rex didn’t show up until 70 million years ago. Sharks make these ancient fossils look like the new kids on the block. The earliest examples people have found are over 450 million years old!

Even if Sharks do lose a tooth, it’s no big deal – they can just grow another one. Unlike humans, Sharks aren’t limited to a puny two sets of teeth. They’re constantly replacing them, and some species get through an incredible 30,000 teeth over their lifetime!

They grow between 8 and 14 feet but can reach up to 23 feet and weigh up to 1.5 tons. Greenland sharks are among the largest sharks in the world, comparable in size to great whites.

Greenland sharks are one of many fish that live in the waters around Greenland, though this is not the only area in which the shark inhabits. These sharks, which are sometimes referred to as “gray sharks” or “gurry sharks,” can also be found in the north Atlantic Ocean near Iceland, Norway, and Canada.

Greenland shark meat can cause symptoms in humans similar to severe inebriation, and the neurotoxins in their flesh can even be incapacitating to sled dogs. This toxicity is due to trimethylamine oxide (TMAO) in the tissue of Greenland shark flesh, which helps the fish stabilize their enzymes and structural proteins against the debilitating effects of severe cold and high water pressure.

Nonetheless, Greenland shark meat can be prepared in a fermentation process that removes the TMAO, resulting in a much-enjoyed national dish of Iceland. This dish, known as Hákarl or kæstur hákarl, is prepared by hanging the meat of the Greenland shark up for four to five months, thus removing the adverse effects of the neurotoxins. This species was not even captured on film for the first time until 1995, and it took 18 more years for anyone to get a video that depicted Greenland sharks in their natural environment.

Greenland Shark Facts

The Greenland shark is an ovoviviparous species, therefore, it retains its eggs within its uterus until delivery. This shark delivers about 10 pups per litter under normal conditions. These pups at birth measure around 15 – 17 inches (38 – 42 cm) in length. They have an unknown gestation period, and they are believed to reach sexual maturity at about 150 years of age.

The Greenland shark is an apex predator and mostly eats fish, and it has been observed actively hunting seals in Canada. The prey found in the stomachs of Greenland sharks is an indicator of the active hunting patterns of these predators.

Recorded fish prey has included smaller sharks, skates, eels, herring, capelin, Arctic char, cod, rosefish, sculpins, lumpfish, wolffish, and flounder. Small Greenland sharks eat predominantly squid, while the larger sharks over 79 inches were discovered eating prey such as epibenthic and benthic fishes as well as seals. The largest of these sharks were found having eaten redfish and other higher trophic level prey.

Using their cryptic coloration, they can approach prey undetected before closing the remaining distance by opening their large buccal cavity in order to create a suction that draws in the prey. This is the likely explanation as to why the gut contents discovered in Greenland sharks are often whole prey specimens.

One of the primary reasons Greenland sharks are spotted so infrequently is their ability to dive to such extreme depths. Researchers have recorded them going as deep as 7,218 feet, and they can sometimes be found relaxing on the slopes and shelves far under the ocean’s surface.

All sharks are cold-blooded, but this particular species truly thrives in a frigid environment. Greenland sharks prefer to stay in water ranging from 30.2 to 50°F, and they migrate to the coldest part of the water each season. Indeed, Greenland sharks are the only known shark species that can tolerate Arctic conditions all year long.

Greenland Shark Facts

Behind the eyes of Greenland sharks are large spiracles that allow them to get oxygen from the water as they swim slowly conserving energy. These holes are more like vestigial gill slits and are larger in this species than in other sharks.

This shark just like another Elasmobranchii has a high concentration of urea and trimethylamine oxide in their tissue. These are nitrogenous waste that helps them maintain an increased buoyancy as well as serve as osmoprotectants. Thus, as urea functions to achieve a balance between water and salt concentrations within the body, it also has the tendency to destabilize protein build-up. This is where the trimethylamine oxide comes in to counteract the urea tendency of destabilizing protein. Another benefit of trimethylamine and urea is to act as antifreeze.

Greenland sharks have a great sense of smell. Of course, there is a need to develop another sense that is not the sense of sight by these sharks. They have parasites attaching to their eyes making them almost blind. This parasite is the copepod Ommatokoita elongata related to lobsters and crabs but has a miniature size due to its parasitic nature. As the shark swims, this parasite tows backward making the shark blind, but this has very little effect on the Greenland shark. Thus, the shark can still differentiate the light and dark, moreover, the depth in which they live is predominantly dark. More so, the depth of the ocean which they inhabit lacks any visible light. Hence, their excellent sense of smell helps them seek out prey and carrion which they feed on.

Many shark species can be aged by counting growth bands on their vertebrae, like rings on a tree. The Greenland shark’s soft vertebrae do not have these bands, however. Instead, its age is determined by removing the layers of the lens of its eye—which continues growing throughout its lifetime—and radiocarbon dating the tissue in the center.

The mystery might have lingered were it not for the work of three Danish scientists—a physicist named Jan Heinemeier and two marine biologists, John Fleng Steffensen, and Julius Nielsen. Nine years ago, Heinemeier and four of his colleagues published a paper on lens crystallines, a class of proteins found in the human eye. Like all organic molecules, crystallines contain carbon, including trace amounts of the radioactive isotope carbon-14[1]. Unlike other proteins, which undergo constant recycling and replenishment, crystallines remain stable throughout a person’s life;

they are envelopes sealed at birth, their contents an artifact from the womb. And, if crystallines are the envelopes, then carbon-14 is the postmark. The isotope has always occurred naturally on Earth, formed wherever incoming cosmic rays strike the atmosphere, but some of the current supply also comes from nuclear weapons tests. The level fluctuates from year to year, and that means that every given time period has its own carbon-14 signature.

(There was a particularly huge spike, called the bomb pulse, in the nuke-happy heyday of the fifties and sixties.) Experimenting on cadavers’ lenses, Heinemeier found that he could measure how much carbon-14 they contained and use it to determine the deceased’s date of birth.

Using this method it has been determined that Greenland sharks can live up to and beyond 500 years. It is firmly established Greenland sharks are the longest-living vertebrates on Earth. In theory, the biggest ones could be nearly six centuries old.

  1. Carbon-14, C-14, 14 C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological, and hydrogeological samples. Carbon-14 was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934. [Back]

Further Reading


Shark Keeper
Fishing Booker
National Ocean Service
The New Yorker
National Geographic
Oceanwide Expeditions

Author: Doyle

I was born in Atlanta, moved to Alpharetta at 4, lived there for 53 years and moved to Decatur in 2016. I've worked at such places as Richway, North Fulton Medical Center, Management Science America (Computer Tech/Project Manager) and Stacy's Compounding Pharmacy (Pharmacy Tech).

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