Greenland shark

Greenland shark
Conservation status
Near Threatened
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Elasmobranchii
Order:	Squaliformes
Family:	Dalatiidae
Genus:	Somniosus
Species:	S. microcephalus
Binomial name
Somniosus microcephalus Bloch & Schneider, 1801
File:Greenland Shark DistMap.png
Range of the Greenland shark

The Greenland shark (Somniosus microcephalus), also known as the sleeper shark, gurry shark, ground shark or grey shark, is a vast shark native to the waters of the North Atlantic Ocean around Greenland and Iceland. These sharks live further north than any other species. They are closely related to the Pacific sleeper shark. The size of the Greenland shark is impressive; it is so large, in fact, that its record surpasses that of the great white shark.

Size

Frequent notes of a 7.3 m (24 ft) specimen exists, and somehow this has come to be accepted as a general maximum length, despite the fact that it is hard to verify this measurement. It seems that, unlike the great white shark, not much time is spent on scrutinizing the alleged measurements for the Greenland shark. It is hardly as famous nor as ferocious as the other predatory sharks. Somewhat more credible is the reports of a 6.4 m (21.3 ft) specimen, caught off the Isle of May, Scotland, in January 1895. The weight was reported at 1,021 kg (2,250 lbs). References exist to a specimen with a weight of 1.4 tons (3,000 lbs), but in this case there is no note of the specimen's length.

Habits and habitat

Greenland sharks are deep-water sharks, living at depths up to 2,000 m (1.24 mi). They feed mainly on fish and sometimes on mammals like seals. The stomachs of a few Greenland sharks have even been found to contain pieces from reindeer, horses, and even parts of a polar bear. An entire reindeer, minus its antlers, was found in the stomach contents of one Greenland shark.

This shark frequently has a relationship with a symbiotic copepod (Ommatokoita elongata) that attaches itself to the cornea of the eye and feeds on the shark's corneal tissue; the resulting scar tissue leads to partial blindness of the shark. The copepod is a whitish-yellow creature that is said to be bioluminescent and possibly serves the symbiotic function of attracting prey for the shark, like a fishing lure. This is suggested by the fact that these normally sluggish sharks have been found with much faster-moving animals (such as squid) in their stomachs.

The flesh of a Greenland shark is poisonous when fresh. This is due to the presence of the toxin trimethylamine oxide, which, upon digestion, breaks down into trimethylamine, producing effects similar to extreme drunkenness. However, it can be eaten if it is boiled in several changes of water or dried or rotted for some months (as by being buried in boreal ground, exposing it to several cycles of freezing and thawing). It is considered a delicacy in Iceland and Greenland.

Research

Canadian researchers with Greenland Shark and Elasmobranch Education and Research Group (GEERG) have been studying the Greenland shark in the Saguenay Fjord and St. Lawrence Estuary since 2001. The Greenland shark has repeatedly been documented (captured or washed ashore) in the Saguenay since at least 1888. Accidental captures and strandings have also been recorded in the St. Lawrence Estuary for over a century. Current research conducted by GEERG involves the study of the behaviour of the Greenland shark by observing it underwater using scuba and video equipment and by placing acoustic and satellite tags (telemetry) on live specimens.

Synonyms

It might be also referred to as Squalus squatina (non Linnaeus, 1758), Squalus carcharis (Gunnerus, 1776), Somniosus brevipinna (Lesueur, 1818), Squalus borealis (Scoresby, 1820), Squalus norvegianus (Blainville, 1825), Scymnus gunneri (Thienemann, 1828), Scymnus glacialis (Faber, 1829), Scymnus micropterus (Valenciennes, 1832), Leiodon echinatum (Wood, 1846), and Somniosus antarcticus (Whitley, 1939).

References

• Template:IUCN2006 Database entry includes justification for why this species is near threatened
• "Somniosus microcephalus". Integrated Taxonomic Information System. 23 January. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)
• Froese, Rainer; Pauly, Daniel (eds.). "Somniosus microcephalus". FishBase. May 2006 version.

External links

• Canadian Museum of Nature SV Greenland Shark