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 Selachi ...

s in the

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

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 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 scavengers with a keen sense of smell and are among the first to arrive at carrion, together with hagfish and rattails. 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 and the bigeyed sixgill shark) were originally known, a third, the Atlantic sixgill shark, 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

* ''Bluntnose sixgill shark, Hexanchus griseus '' {Pierre Joseph Bonnaterre, Bonnaterre, 1788) (bluntnose sixgill shark) * ''Bigeyed sixgill shark, Hexanchus nakamurai'' Teng Huo-Tu, Teng, 1962 (bigeyed sixgill shark) *''Atlantic sixgill shark, Hexanchus vitulus'' Stewart Springer, Springer & Waller, 1969 (Atlantic sixgill shark)

Extinct species

* ''Hexanchus agassizi'' Henri Cappetta, Cappetta, 1976 * ''Hexanchus andersoni'' Jordan, 1907 * ''Hexanchus casieri'' Kozlov, 1999 * ''Hexanchus collinsonae'' Ward, 1979 * ''Hexanchus gracilis'' Davis, 1887 * ''Hexanchus hookeri'' Ward, 1979 * ''Hexanchus microdon'' Louis Agassiz, Agassiz, 1843 * ''Hexanchus tusbairicus'' Kozlov in Zhelezko & Kozlov, 1999

References

External links

* * * * * * Hexanchus, 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