The Greenland shark (Somniosus microcephalus), also known as the Gurry shark or grey shark, or by the Kalaallisut name eqalussuaq, is a large shark of the family Somniosidae (“sleeper sharks”), closely related to the Pacific and southern sleeper sharks. The distribution of this species is mostly restricted to the waters of the North Atlantic Ocean and Arctic Ocean. It has the longest known lifespan of all vertebrate species (estimated to be between 300–500 years) and is among the largest extant species of shark. As an adaptation to living at depth, it has a high concentration of trimethylamine N-oxide in its tissues, which causes the meat to be toxic. Greenland shark flesh treated to reduce toxin levels is eaten in Iceland as a delicacy known as kæstur hákarl (Praebel, K. 2017).
Family: Somniosidae – Sleeper Sharks
Genus: Somniosus
Species: microcephalus
Phylum– Chordata
Class– Chondrichthyles
Subclass– Elasmobranchii
Family– Somniosidae (Dalatiidae)
Genus– Somniosus
Species– microcephalus
Status: IUCN Red List Near Threatened
Average Size and Length: 18+feet
Average Weight: 2200+ pounds
Current Rare Mythical Sightings: Greenland sharks are a common subject of Inuit legends (called eqalussaq). Some common nicknames are the sleeper shark, the gurry shark, ground shark, and the hakjerring as named by the Norwegians.
For centuries they were only known to the Inuit. These people would use the meat of Greenland sharks to feed their dogs, although the meat would have to be treated first, being it is filled with toxins that could kill dogs or humans if ingested untreated.
Teeth and Jaw: It has 100+ small teeth. They are narrow and smooth on the edges. They are sharper on the upper jaw and wider, larger with pointed tips on the lower jaw.
Head: The Greenland shark has a short-rounded snout. It has two distinct blind eyes on the side of its head, usually inhabited with a single copepod parasite.
Tail: The Greenland shark has a broad tail, confirming its ability to reach bursts of speed.
Demographic, Distribution, Habitat, Environment and Range: The Greenland shark inhabits cold, deep water, polar regions. Typically, in waters 35-45 degrees F (2-7 degrees C). On rare occasions they will visit shallower bays and estuaries (probably during spring and summer). Greenland sharks usually stay within depths between 1000 to 2000 feed all the way down to 6500 feet. The typical range of a Greenland shark is in the cold waters of North Atlantic all the way west, and as south as the Gulf of the Saint Lawrence. The Greenland shark is found the farthest north almost more than any other shark species. Occasionally found in Portugal.
Diet: The Greenland shark is a known scavenger, but current research is suggesting that it may hunt as well. The typical diet of Greenland sharks includes some fast swimming fish such as salmon. They are also known to eat seals, narwal, right wales, beluga, and squid. Its stomach has shown contents of land-dwelling mammals. The Greenland shark is also known to be cannibalistic.
Ram-Suction Index: Observations of Greenland shark feeding show that this species uses a powerful inertial suction mode of feeding and was able to draw bait into the mouth from a distance of 25-35 cm (Grant, Scott M; Sullivan, Rennie; Hedges, Kevin J. 2018-01-01.)
Greenland sharks are also seen using a twisting Greenland sharks have heterodonty, saw-like teeth in the lower jaw and thin, piercing teeth in the upper jaw.
Aesthetic Identification: The Greenland shark is grey, brown to dark grey or dark brown, and sometimes even appearing black or purplish in color. The Greenland shark may appear patchy with dark or pale patches on the flanks. The Greenland shark will appear to have copepods on the eyes. The Greenland shark has rough skin with denticles that are hook-like erect cusps.
Biology and Reproduction: The Greenland shark has two small dorsal and pectoral fins and no anal fin. It has a long lower caudal lobe with a short caudal peduncle, lateral keels on the base of the caudal fin.
The Greenland shark is Ovoviviparous, yet mating season and gestation is still unknown. It is unclear as to when the Greenland sharks reach sexual maturity, but research suggests that females are at least 9 feet. The litter size is also unclear, but research suggests possibly 10 pups averaging 13-16 inches long.
They have an extremely slow metabolism and heart rate.
The lifespan of a Greenland shark is now known to be 300-500 years. The Greenland shark is one shark that has found the fountain of youth. Friend and Professor of Marine Ecology at the Arctic University of Norway, Dr. Kim Praebel has taken DNA from over 100 Greenland Sharks that are at least 300 years old. He plans to compare this DNA with other shark species to attempt to identify mutations that can stop cancer cells and fight off forms of virus and bacteria. Radiocarbon dating of eye lens nuclei from 28 female Greenland sharks (81 to 502 cm in total length) revealed a life span of at least 272 years.
Dr. Praebel’s research will also help to identify the secrets to life longevity, Dr. Praebel may have found the fountain of youth in one of the most amazing sharks on the planet. His official research can be requested through UiT here
Urea exists as a destabilizer of proteins. Urea’s function is to help the balance of salt concentration in the body to match the salt concentration in the outside environment. It exists in high concentrations in the muscles of cartilaginous fishes. The high concentrations of urea must be counteracted to protect the tissues because urea alone can be toxic. Trimethylamine oxide, or TMAO is a protein stabilizer that exists to counteract the high levels of urea. The ratio of urea to TMAO is 2:1, however, Greenland sharks (Somniosus microcephalus) have a much higher level of urea and TMAO than most other sharks (Praebel, K. 2019). Perhaps the reasoning is to protect the shark at depths through its extremely long lifetime. Therefore, the meat of a Greenland shark is toxic, and if consumed, it must be treated to reduce the toxins first.
Sensing and Intelligence: Like all sharks, Greenland sharks rely heavily on sensing electrical currents through their Ampullae of lorenzini and their lateral lines.
However, this shark is blind, therefore vision is not high on the list; the copepod attached to the Greenland shark’s eye is unique to the Greenland shark, and renders the shark blind. Therefore, they primarily use their sense of smell to locate prey as well as scavenge dead carcasses.
Evolution suggests that since this shark spends most of its time in the deep dark void below, it has evolved to be blind. The Greenland shark has a unique species of copepods only growing on their eyes, which in turn renders them blind. Most Greenland sharks are partially or eventually become completely blind due to these unique parasitic copepods called Ommatokoita, which is a type of crustacean. Ommatokoita attach to the outer part of the front of the eye, which is the cornea.
The Greenland shark does compensate with a strong sense of smell.
One other interesting trait of a Greenland shark is that its skin is poisonous or toxic. When freshly caught, Inuit risk becoming intoxicated, similar to being drunk. They must boil the flesh to remove the poison.
Speed: Typically, a sluggish shark, but on the other side, it is capable of bursts of speed to catch living prey. Their low metabolic rate allows them to store energy, which could also be a factor to their overall longevity and success. They typically swim at a rate of half a mile per hour.
Greenland Sharks Future and Conservation: Contact us for details.
Greenland Shark Recorded Attacks on Humans: None. There are Inuit fokelore tall tales suggesting eqalussaq attacking kayaks. At its worse, Greenland sharks are just a nuisance stealing fisherman’s catches and scavenging their catches.