The Greenland shark (Somniosus microcephalus) also known as the gurry shark or grey shark, or by the Inuit name Eqalussuaq, is a large shark of the family Somniosidae ("sleeper sharks") that is native to the waters of the North Atlantic Ocean around Canada, Greenland, and Iceland. These sharks live farther north than any other shark species.
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Many of the species' adaptations are due to it being the only truly sub-Arctic species of shark. They are closely related to the Pacific sleeper shark. This is one of the largest living species of shark, of dimensions comparable to those of the great white shark. Greenland sharks grow to 6.4 m (21 ft) and 1,000 kg (2,200 lb), and possibly up to 7.3 m (24 ft) and more than 1,400 kg (3,100 lb).
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However, most Greenland sharks observed have been around 2.44-4.8 m (8.0-16 ft) long and weigh up to 400 kg (880 lb). Males are typically smaller than females. It rivals the Pacific sleeper shark (possibly up to 7 m or 23 ft long) as the largest species in the family Somniosidae. The Greenland Shark is a thickset species with a short, rounded snout, small eyes, and very small dorsal and pectoral fins.
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The gill openings are very small for the species' great size. Coloration can range from pale creamy-gray to blackish-brown and the body is typically uniform in color, though whitish spots or faint dark streaks are occasionally seen on the back. Due to their cold environments, Greenland Sharks are thought to grow at a very slow rate. There are no reliable data on their life span, but fully grown Greenland sharks have been recaptured 16 years after being tagged.
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As recently as 1957 it was found that the females do not deposit eggs in the bottom ooze, but retain the developing embryos within their bodies so that they are born alive after an undetermined gestation period. 10 pups per litter is normal, each initially measuring some 90 cm (35 in) in length. The flesh of a Greenland shark is poisonous. This is due to the presence of the toxin trimethylamine oxide, which, upon digestion, breaks down into trimethylamine, producing effects similar to extreme drunkenness.