The sixgill sharks are a genus, ''Hexanchus'', of deepwater

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

s in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Hexanchidae. These sharks are characterized by a broad, pointed head, six pairs of

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

slits, comb-like, yellow lower teeth, and a long tail. The largest species can grow up to 8 m long and weigh over 600 kg (1320 lb). They are continental shelf-dwelling and

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between and . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. T ...

scavengers with a keen sense of smell and are among the first to arrive at carrion, together with

hagfish Hagfish, of the class Myxini (also known as Hyperotreti) and order Myxiniformes , are eel-shaped, slime-producing marine fish (occasionally called slime eels). They are the only known living animals that have a skull but no vertebral column, a ...

and

rattails Grenadiers or rattails are generally large, brown to black gadiform marine fish of the subfamily Macrourinae, the largest subfamily of the family Macrouridae. Found at great depths from the Arctic to Antarctic, members of this subfamily are ...

. They show a characteristic rolling motion of the head when feeding. They have been found at depths of up to . Though only two extant species (the

bluntnose sixgill shark The bluntnose sixgill shark (''Hexanchus griseus''), often simply called the cow shark, is the largest hexanchoid shark, growing to in length. It is found in tropical and temperate waters worldwide and its diet is widely varied by region. The ...

and the

bigeyed sixgill shark The bigeyed sixgill shark (''Hexanchus nakamurai'') is a cow shark of the family Hexanchidae. Its dorsal surface has a brownish-gray color, and is sharply separated from the light coloring of its ventral surface. The eyes are a fluorescent gree ...

) were originally known, a third, the

Atlantic sixgill shark The Atlantic sixgill shark (''Hexanchus vitulus'') is a rare species of hexanchid shark found in the Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% ...

, was found to exist.

Swimming behavior

The bluntnose sixgill shark, ''Hexanchus griseus'', is relatively common to scientists. However, very little information exists about its distribution patterns, migrations and behavior. Data on occurrence and behavior of sixgill sharks inhabiting waters north of Spain (Galicia and Cantabrian Sea, NE Atlantic) were obtained from yearly oceanographic trawl surveys. Data obtained from one electronic pop-up tag (Mini PAT), provided information about depth and temperature preferences over 75 days. Mean depth obtained during that period was 913 m (depth range 727–1247 m), and the mean temperature was 10.3 °C, (range 8.0–10.8 °C). Movements up and down in the water column within a single day ranged from 50 to 385 m. No cyclic diel vertical migration was however observed, the shark moved smoothly without a defined pattern. The six-gill sharks have the ability to alter their feeding behaviors due to the situation that they are in. A feeding behavior analysis displayed that the six-gill sharks are able to utilize a bite of food compared to other aquatic vertebrates.

Extant species

* ''

Hexanchus griseus The bluntnose sixgill shark (''Hexanchus griseus''), often simply called the cow shark, is the largest hexanchoid shark, growing to in length. It is found in tropical and temperate waters worldwide and its diet is widely varied by region. The ...

'' { Bonnaterre, 1788) (bluntnose sixgill shark) * ''

Hexanchus nakamurai The bigeyed sixgill shark (''Hexanchus nakamurai'') is a cow shark of the family Hexanchidae. Its dorsal surface has a brownish-gray color, and is sharply separated from the light coloring of its ventral surface. The eyes are a fluorescent gre ...

Teng Teng may refer to: *Teng (surname) (滕), a Chinese surname *Teng (state), an ancient Chinese state *Teng (mythology), a flying dragon in Chinese mythology *Teng County Teng County or Tengxian (; za, Dwngz Yen) is a county of eastern Guangxi, C ...

, 1962 (bigeyed sixgill shark) *''

Hexanchus vitulus The Atlantic sixgill shark (''Hexanchus vitulus'') is a rare species of hexanchid shark found in the Atlantic Ocean. It was formerly described as its own species, but was synonymised with the bigeye sixgill shark The bigeyed sixgill shark ( ...

Springer Springer or springers may refer to: Publishers * Springer Science+Business Media, aka Springer International Publishing, a worldwide publishing group founded in 1842 in Germany formerly known as Springer-Verlag. ** Springer Nature, a multinationa ...

& Waller, 1969 (Atlantic sixgill shark)

Extinct species

* ''

Hexanchus agassizi The sixgill sharks are a genus, ''Hexanchus'', of deepwater sharks in the family (biology), family Cow shark, Hexanchidae. These sharks are characterized by a broad, pointed head, six pairs of gill slits, comb-like, yellow lower teeth, and a long ...

'' Cappetta, 1976 * '' Hexanchus andersoni'' Jordan, 1907 * ''

Hexanchus casieri The sixgill sharks are a genus, ''Hexanchus'', of deepwater sharks in the family Hexanchidae. These sharks are characterized by a broad, pointed head, six pairs of gill slits, comb-like, yellow lower teeth, and a long tail. The largest species ca ...

'' Kozlov, 1999 * '' Hexanchus collinsonae'' Ward, 1979 * ''

Hexanchus gracilis The sixgill sharks are a genus, ''Hexanchus'', of deepwater sharks in the family Hexanchidae. These sharks are characterized by a broad, pointed head, six pairs of gill slits, comb-like, yellow lower teeth, and a long tail. The largest species ca ...

'' Davis, 1887 * '' Hexanchus hookeri'' Ward, 1979 * ''

Hexanchus microdon The sixgill sharks are a genus, ''Hexanchus'', of deepwater sharks in the family Hexanchidae. These sharks are characterized by a broad, pointed head, six pairs of gill slits, comb-like, yellow lower teeth, and a long tail. The largest species ca ...

'' Agassiz, 1843 * '' Hexanchus tusbairicus'' Kozlov in Zhelezko & Kozlov, 1999

References

External links

* * * * * * Sinemurian genus first appearances Extant Early Jurassic first appearances Shark genera Taxa named by Constantine Samuel Rafinesque {{Shark-stub

Swimming behavior

Extant species

Extinct species

See also

References

External links