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Somniosus microcephalusGreenland shark(Also: gray shark; sleeper shark)

By Patrick Mills

Geographic Range

Somniosus microcephalus is found in the north Atlantic, from the coast of New England and Canada to Scandinavian waters. They occasionally venture as far south as the mouth of the Seine River in France. (Compagno and Fowler, 2005; Compagno, 1984; Compagno and Fowler, 2005; Compagno, 1984)

Habitat

Somniosus microcephalus live mainly on continental and insular shelves. They occupy intertidal regions in addition to some river mouths and shallow bay areas during the winter months and often move to depths from 180 to 550 meters during warmer months. They have been observed as low as 1200 meters, with one observation at 2200 meters off the coast of Georgia - extending its range both geographically and in terms of depth. In northern parts of their range, Greenland sharks are found from 0 to 1200 meters in waters from 1 to 12 degrees Celsius. In southern parts of their range, these sharks may occur at greater depths. (Compagno and Fowler, 2005; Compagno, 1984)

  • Range depth
    145 to 1200 m
    475.72 to 3937.01 ft
  • Average depth
    180-550 m
    ft

Physical Description

Somniosus microcephalus is a large, sluggish shark that averages between 2 and 4 meters in length. Most of the body is a medium grey or brown in color and sometimes exhibits dark transverse bands or small spots or blotches that are lighter or darker than the base color. The snout is short and rounded, and the body is heavy and cylindrical in shape with small precaudal fins. No spines are present in the two equally-sized dorsal fins, and the ventral lobe of the caudal fin is slightly elongated. No anal fin is present. The skin is quite rough, exhibiting denticles with curved pointed cusps. Teeth in the upper and lower jaws differ in shape; upper teeth are spear-shaped while the lower teeth are shaped with high roots and low bent cusps for slicing. (Compagno and Fowler, 2005; Compagno, 1984; Compagno and Fowler, 2005; Compagno, 1984)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range mass
    700 to 1000 kg
    1541.85 to 2202.64 lb
  • Range length
    40 to 640 cm
    15.75 to 251.97 in
  • Average length
    244 to 427 cm
    in

Development

Development in Somniosus microcephalus is ovoviviparous; litters of up to ten pups have been observed. Size of fully grown young at birth has not been confirmed but is thought to be around forty centimeters. Most adults grow to between two and four meters in length. (Compagno, 1984)

Reproduction

Mating by this species has never been observed, but females have been found with mating scars on their caudal fins. Therefore, it is inferred that, as is the case with most sharks, males bite females until they submit. Fertilization occurs internally. ("Greenland Shark and Elasmobranch Research and Education Group", 2005)

Mating has never been observed in this species and little information is available concerning reproduction in Greenland sharks or related species. ("Greenland Shark and Elasmobranch Research and Education Group", 2005; Compagno and Fowler, 2005; Compagno, 1984)

  • Average number of offspring
    10

There is no specific information on parental investment in Greenland sharks. However, most sharks are independent immediately after birth. Females provide developing embryos with rich food sources to support their development.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

No specific information about the longevity of Somniosus microcephalus exists. Some scientists speculate that these sharks may live in excess of 100 years. ("Greenland Shark and Elasmobranch Research and Education Group", 2005)

Behavior

Somniosus microcephalus is generally described as a sluggish. They spend much of their time hovering near the sea floor in search of food. They may also be capable of pursuing prey. These sharks have been observed exhibiting the behavior of animals that often prey on seals, even stalking a camera operator in one rare instance. However, no attacks on humans by this species have been confirmed. Greenland sharks are solitary, outside of the mating season or when large groups occur to exploit carrion, such as that produced by the commercial fishing industry. ("Greenland Shark and Elasmobranch Research and Education Group", 2005; Compagno and Fowler, 2005; Compagno, 1984; "Greenland Shark and Elasmobranch Research and Education Group", 2005; Compagno and Fowler, 2005; Compagno, 1984)

Communication and Perception

Like all sharks, Somniosus microcephalus has a lateral line which aids in the detection of movement in the surrounding waters. Sharks also have especially keen chemical perception. No communication has been observed within the species. ("Greenland Shark and Elasmobranch Research and Education Group", 2005)

Food Habits

Fish, marine mammals, and carrion are three staples in the diet of Somniosus microcephalus. Fish include herring (Clupeinae), salmon (Salmonidae), smelt (Osmeridae), cod (Gadidae), pollock (Theragra), haddock (Melanogrammus), halibut (Hippoglossus), redfish (Hoplostethus), sculpins (Cottoidei), lumpfish (Cyclopterus), and skates (Rajiformes). Seals (Phocidae) and small whales (Delphinidae) are also common food items. Drowned horses and reindeer have also been found in the stomachs of captured specimens. Somniosus microcephalus has been observed feeding in great numbers on carrion produced by commercial whaling and fishing operations. (Compagno and Fowler, 2005; Compagno, 1984)

  • Animal Foods
  • mammals
  • fish
  • carrion
  • mollusks
  • aquatic crustaceans
  • echinoderms
  • cnidarians

Predation

There are no known predators of adult Greenland sharks because of their very large size. (Eagle, 2006)

Ecosystem Roles

Many of these sharks have copepod parasites, Ommatokoita elongata, attached to the corneas of their eyes. A single, female copepod will attach itself to one of the corneas, resulting in corneal damage and blindness in one eye. This does not seem to negatively effect the shark, as they do not rely on their vision. It has been suggested that the bioluminescence of these parasites helps lure prey, thus resulting in a mutualistic relationship, but there is no evidence to support this. (Compagno and Fowler, 2005; Compagno, 1984)

Mutualist Species

Economic Importance for Humans: Positive

Somniosus microcephalus is commonly fished by people in the Arctic regions (Norway, Iceland, and Greenland) for its liver oil and meat. People of the Inuit tribes have also been known to use its skin to make boots and its teeth as knives. (Compagno and Fowler, 2005; Compagno, 1984)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Unless properly washed or dried, Greenland shark meat is toxic to humans. Like most sharks, Greenland sharks rarely attack unless harassed. (Compagno and Fowler, 2005; Compagno, 1984)

Conservation Status

The status of Greenland shark populations are not well known. They support a fishery for liver oil in Greenland, Norway, and Iceland, but some researcher suspect that populations have diminished. They have an estimated population doubling time of 14 years. (Compagno and Fowler, 2005)

Other Comments

Greenland sharks are also known as sleeper sharks, ground sharks, gray sharks, and gurry sharks. They are known as ekalugssuak in Greenland, hakarl in Iceland, and hakjerring in Norway. (Eagle, 2006)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Patrick Mills (author), University of Michigan-Ann Arbor, Kevin Wehrly (editor, instructor), University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

electric

uses electric signals to communicate

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

vibrations

movements of a hard surface that are produced by animals as signals to others

References

2005. "Greenland Shark and Elasmobranch Research and Education Group" (On-line). Accessed October 18, 2005 at http://www.geerg.ca.

Compagno, L. 1984. FAO Species Catalogue Volume 4:Sharks of the World. Rome: United Nations Development Programme.

Compagno, L., S. Fowler. 2005. Sharks of the World. Princeton, New Jersey: Princeton University Press.

Eagle, D. 2006. "Biological Profiles: Greenland shark" (On-line). Florida Museum of Natural History, Ichthyology Department. Accessed February 10, 2006 at http://www.flmnh.ufl.edu/fish/Gallery/Descript/GreenlandShark/GreenlandShark.html.

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