Greenland shark (Somniosus microcephalus) is the largest species of the dogfish family that inhabits the icy waters of the Arctic and the northern Atlantic. It is also known by other names such as the gurry shark, gray shark, and sleeper shark. The inhabitants of the Arctic call it by the name 'Eqalussuaq'. Here are some interesting facts about the Greenland shark. Classification Kingdom: Animalia Phylum: Chordata Class: Chondrichthyes Subclass: Elasmobranchii Order: Squaliformes Family: Somniosidae Genus: Somniosus Greenland sharks are found in the Arctic ocean and north of Atlantic ocean from the coast of New England and Canada to the Scandinavian waters. In Canadian waters, they can be found around Baffin Island, the Gulf of St. Lawrence, and the Scotian Shelf. They are also spotted near the mouth of Saguenay river in Quebec. They can be found in the Gulf of Maine and the Gulf of Mexico towards the south of the north Atlantic ocean. They prefer to inhabit freezing cold waters with temperatures between -1°C to 10°C. In the summer, they spend most of their time in the deepest parts of the ocean where the water is the coldest. They can be found anywhere from 180 to 730 meters deep in the ocean. During the winter, they tend to swim towards the surface of the ocean, where the water is colder compared to the water on the ocean floor. They usually grow up to 21 feet and weigh approximately 2,000 lbs. They have a cylindrical body, which is entirely covered with dermal denticles (skin teeth). The head is small with a short, rounded snout and tiny eyes. The skin is grayish in color and is usually marked with white spots or dark bands. The gill slits are small in size and are located low on the side of the head. The dorsal fins are small, spineless and are located in the middle of the shark's trunk. Anal fins are absent, while the caudal fin is asymmetrical in shape. The teeth in the upper jaw are small, thin, and sharp, whereas the lower jaw teeth are comparatively large, broad, and smooth. Females are larger than the males. Also, their skin is twice as thick as the males. They reproduce via aplacental viviparity. Aplacental viviparity is a mode of reproduction in sharks where the eggs hatch and the young ones develop inside the female's body in the absence of a placenta. The females usually give birth to a litter of about 10 pups. The pups are about 1-2 feet in length at birth. Males bite the females until they submit themselves for mating. The Greenland shark is primarily a scavenger. It can feast on anything that seems like food. It feeds on a variety of prey including invertebrates, fish, seabirds, sea mammals, and dead rotten animals. Some Greenland sharks have been found to have fed on the carrion of horses, reindeer, and polar bears. Sometimes, they even participate in cannibalism. The Greenland shark is not listed as a threatened species by the COSEWIC (Committee on the Status of Endangered Wildlife in Canada). However, according to the IUCN Red List (International Union for the Conservation of Nature and Natural Resources), it is a near-threatened species. According to some researchers, the populations of Greenland sharks have decreased as they are hunted down for liver oil and meat in Greenland, Norway, and Iceland. Though some countries including Canada have banned hunting of these sharks, their numbers are still declining, raising a future cause for concern. Greenland shark is the second-largest carnivorous shark in the world, the largest being the white shark. It is the largest fish in the Arctic. It is the only shark which prefers to live in extremely cold waters of the arctic and sub-arctic. It is believed to have a life-span of more than 150 years. It has been primarily hunted for its liver oil. Due to its sluggish movement, it seems to be sleeping all the time. Therefore, it is also known as the sleeper shark. A parasite called copepod lives and feeds on the Greenland shark's corneal tissue, and over time, severely damages its eyesight. The Greenland shark shares a symbiotic relationship with the copepod, Ommatokoita elongata. This copepod is bioluminescent. It glows in the dark waters and helps the shark to attract prey. In return, the parasite gets to feed on the shark's corneal tissue. Fresh meat of the Greenland shark is poisonous for consumption. This is owing to the fact that the flesh contains high concentrations of trimethylamine oxide, which induces an intoxicating effect on digestion. The meat also contains high levels of urea. Hence, the shark has a strong urine-like odor. The sperm whale is the only confirmed predator of the Greenland shark.