Goblin Shark

>> Friday, March 16, 2012

Goblin Shark also called Mitsukurina owstoni, is a deep-sea shark, the sole living species in the family Mitsukurinidae. The most distinctive characteristic of the goblin shark is the unusual shape of its head. It has a long, trowel-shaped, beak-like rostrum or snout, much longer than other sharks' snouts. Some other distinguishing characteristics of the shark are the color of its body, which is mostly pink, and its long, protrusible jaws. When the jaws are retracted, the shark resembles a pink grey nurse shark, Carcharias taurus, with an unusually long nose.

Mitsukurina owstoni is found in the deep ocean, far below where the sun's light can reach at depths greater than 200 m. They can be found throughout the world, from Australia in the Pacific Ocean to the Gulf of Mexico in the Atlantic Ocean. They are best known from the waters around Japan, where the species was first discovered.
Scientific classification
Kingdom - Animalia
Phylum - Chordata
Class - Chondrichthyes
Subclass - Elasmobranchii
Order - Lamniformes
Family - Mitsukurinidae D. S. Jordan, 1898
Genus - Mitsukurina D. S. Jordan, 1898
Species -  M. owstoni

Distribution and habitat
Mitsukurina owstoni is a bathydemersal deep-water shark usually found near the sea bottom, at depths of around 250 m. The deepest specimen ever caught was found at 1,300 m. Most goblin sharks that have been caught were from Japan (where it was first discovered), specifically in an area between Tosa Bay and Boso Peninsula. The species' Pacific range is rather large. M. owstoni specimens have been found in the waters off South Africa, from various sites throughout the western Pacific Ocean. Goblin sharks have also been found off the coasts of Australia and New Zealand.

Anatomy and appearance
Goblin sharks can grow to 11 feet (3.3 m) long and weigh 350 lb (159 kg). They have the typical shark's semi-fusiform body. Unlike the common image of sharks, M. owstoni's fins are not pointed and instead are low and rounded, with the anal and pelvic fins significantly larger than the dorsal fins. Their heterocercal tails are similar to the thresher shark's, with the upper lobe significantly longer proportionately than other sharks'. In addition, the goblin shark's tail lacks a ventral lobe. The pink coloration, unique among sharks, is due to blood vessels underneath a semi-transparent skin (which bruises easily), thereby causing the coloring. The fins have a bluish appearance. Goblin sharks lack a nictitating membrane. They have no precaudal pit and no keels. The front teeth are long and smooth-edged, while the rear teeth are adapted for crushing. Up to 25% of the goblin shark's body weight can be its liver. This is similar to other sharks, such as the basking shark and the frilled shark, and contributes to the buoyancy of the shark, which, like all sharks, lacks a swim bladder.
Goblin sharks hunt by sensing the presence of prey with electro-sensitive organs in the rostrum, or snout, due to the absence of light in the deep waters where it swims. Once a shark finds its prey, it suddenly protrudes its jaws, while using a tongue-like muscle to suck the victim into its sharp front teeth. They have been known to feed on deep-sea rockfish (Helicolenus dactylopterus was found in one specimen), cephalopods and crustaceans.

Next to nothing is known of the goblin shark's reproductive habits. Even though a pregnant goblin shark has never been caught or found, as members of the order Lamniformes, they are assumed to be ovoviviparous; their eggs mature and hatch inside the mother's body and the shark gives birth to live young.
Role in the ecosystem
The goblin shark is an upper-level carnivore in its natural habitat. As a macro-organism, it has its fair share of external and internal parasites. Two new species of tapeworm were discovered in a specimen captured off Australia, Litobothrium amsichensis and Marsupiobothrium gobelinus.

Conservation status
In 2004, Mitsukurina owstoni was classified by the IUCN's Shark Red List Authority as a species of "Least Concern". The rationale given was that despite the fact that goblin shark sightings have been relatively rare, the worldwide distribution of the species, combined with the fact that it was not accidentally taken often as bycatch in fisheries, ensured that the species is most probably not in any reasonable danger of extinction. The IUCN described the major threats to M. owstoni populations' as either harvesting (as an intentional target for fishing), accidental mortality (bycatch) and to a lesser extent, water pollution. There are no active conservation efforts being made toward this specific species.

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