Bluntnose sixgill shark

2/16/2016

We bring you…. drumroll, please… the bluntnose sixgill shark (Hexanchus griseus)!
Other common names include, “cow shark” and “mud shark," and they’re actually a pretty common, large deep water shark (up to 5.4 m /18 ft large; females tend to be bigger than males).

They are one of the few members in the Hexanchidae family, and this shark has an unusual number of gill slits (six). Their coloration varies from brown, gray or even black, with small, bright green eyes that have a large, black pupil.

They are a pretty stocky animal, with a rounded, blunt snout. They have one dorsal fin and it’s like all the way back, by the tail. This shows that they’re slow, sluggish swimmers but can be pretty persistent when chasing after their food (crustaceans, fish, rays, dead mammals and cephalopods).

Sixgill sharks are pretty cosmopolitan, often found at depths of about 90 m (300 ft), but sometimes found in the shallows and can come in contact with divers; but no worries, they aren’t dangerous. In fact, they tend to stick to themselves… which is why we don’t really know much about their reproductive tendencies, or much at all. We do know they’re viviparous with yolk-sac, and can have anywhere from 22 to 108 pups born (WOAH).

There’s probably a really high mortality rate and not many survive to maturity (apparently they can live up to 80 years). According to the IUCN, they are assessed as Near Threatened (NT). However, since we know so little about them… it sadly could be worse.

ever gone diving with these sharks before?

glossary

Cephalopods: The most intelligent, mobile, and largest of all molluscs. These include: squid, octopuses, cuttlefish, the chambered nautilus, and their relatives.
Cosmopolitan: Worldwide distribution.
Crustaceans: Group of animals with a hard exoskeleton, jointed legs and segmented body.
Dorsal fin: Fin located on the back.
IUCN: International Union for Conservation of Nature.
Pelvic fins: Fins located behind the gills on either side.
Pups: Baby sharks.
Viviparous with yolk-sac: Also known as aplacental viviparous and previously known as ovoviviparous/ovoviviparity; it is the production of eggs that are fertilised and hatch inside the female shark but the embryos lack a placental connection to the oviduct or uterus and so do not feed off the mother.