The Atlantic sixgill shark (''Hexanchus vitulus'') is a rare species of hexanchid

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

found in the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

at depths that are greater than 300 meters. These depths are known as mesopelagic and bathypelagic in tropical and temperate waters around the world. The Atlantic sixgill shark is very similar to other species of sixgill in terms of its growth rate in deep sea waters. It is believed that this is due to the abiotic and biotic factors in relation to the depths at which they are found. It was formerly described as its own species, but was synonymised with the

bigeye 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 ...

(''Hexanchus nakamurai''). However, a study published in 2019 resurrected the species on the basis of molecular data. The species can be physically differentiated from the bluntnose sixgill shark (''Hexanchus griseus'') by its much smaller size and position of the dorsal fin in relation to the caudal fin.Daly-Engel, T. S., Baremore, I. E., Grubbs, R. D., Gulak, S. J., Graham, R. T., & Enzenauer, M. P. (2019). Resurrection of the sixgill shark Hexanchus vitulus Springer & Waller, 1969 (Hexanchiformes, Hexanchidae), with comments on its distribution in the northwest Atlantic Ocean. Marine Biodiversity, 49(2), 759–768. The Atlantic sixgill shark (''Hexanchus vitulus'') becomes sexually mature at around 1.40 to 1.75 meters. They do not reach lengths much greater than 180 cm.

Diet

Their diet consists mainly of bony fish and cephalopods, with crustaceans sometimes included. An experiment shows that the Atlantic sixgill shark will not feed on prey after it has been dead for 24 hours, it will ignore said prey and move on to its next kill. They will also feed more on the prey in the spring season as compared to the winter season.

Classification

Although the Atlantic sixgill shark was believed to be the only species in its genus it has been discovered that there are two other extant species in the genus ''

Hexanchus 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 c ...

'': the

Bigeye 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 ...

(''Hexanchus nakamurai)'' and the

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

''(Hexanchus griseus)''. One main difference between ''H. vitulus'' and ''H. griseus'' are that ''H. vitulus'' has five rows of teeth on either side of its lower jaw while ''H. griseus'' has six.

References

Hexanchus Fish described in 1969 {{shark-stub