The blutnose six-gill shark often also known as the cow shark, is possibly one of the most mysterious members of the shark family as they are seldom sighted by divers and almost nothing is known about them.
Marine Biologist believe that the Bluntnose shark is the only surviving species of shark which is genetically similar to prehistoric sharks making them almost living fossils. These sharks are one of the largest predatory sharks in the world and can grow up to 5.4 m (18 ft) in length and have skin coloration ranging from light brown to a darker black. The easiest way to distinguish this type of shark is by observing their head shape which true to its name, is snubbed or blunt-nosed ending abruptly; also unlike other sharks the six-gill has only one dorsal fin which is located on the back of its body near its tail and isn’t as prominent as an ordinary shark’s. This shark is also unique to all others as it has six gill slits to breathe from on the side of its head as opposed to the usual five.
The reason behind the bluntnose shark’s unique six gills is to help it breathe in its natural habitat which is typically in ocean depths exceeding 90m (300ft) and recorded to inhabit depths of up to 1875m (6,150ft) below sea level. Like several deep dwelling creatures of the ocean, the Six-gill is known to migrate each night towards the surface to feed and return to the depths before dawn.
Sighting a six-gill sharks is extremely difficult, despite the fact that they are perhaps the widest distribution of all sharks and are found all over the world in both tropical and temperate waters. Since the only time a diver can spot a six-gill is on a night dive and in certain locations especially where upward currents force the creature to rise to shallower than normal waters. This shark is not considered dangerous to humans and there have been no reported attacks attributed to the six-gill to date.
photos from NOAA Office of Ocean Exploration and flickr.com by Traumador, Dan Hershman,
