all incredible world: Weird sharks

Thursday, April 5, 2012

Weird sharks


 Cookiecutter Shark
The cookiecutter shark is a small, rarely-seen dogfish shark. It is the smallest shark on this list but its unusual eating habits earn it a place. The cookiecutter shark derived its name from its habit of removing small circular plugs (like cookie cutters) of flesh and skin from cetaceans and large fish, including other sharks. It is hypothesized that the shark attaches to its much larger prey with its suctorial lips and modified pharynx, then rotates its body to achieve a highly symmetrical cut. They are considered parasites, with hosts such as the Megamouth shark. Cookiecutters seem to be attracted to undersea electrical cables, and one may find round bite marks in them. There has been one suspected attack on a human.

 Whale Shark
The whale shark, Rhincodon typus, is a slow moving filter feeding shark that is the largest living fish species. It can grow up to 40 ft in length and can weigh up to 15 short tons. The shark is found in tropical and warm oceans and lives in the open sea and can live for about 70 years. The species is believed to have originated about 60 million years ago. Despite its enormous size, the whale shark does not pose any significant danger to humans. It is a frequently cited example when educating the public about the popular misconceptions of all sharks as “man-eaters”. They are actually quite gentle and can be playful with divers. Divers and snorkelers can swim with this giant fish without any risk apart from unintentionally being struck by the shark’s large tail fin.
 Megamouth Shark
The megamouth shark is an extremely rare species of deepwater shark. Since being discovered in 1976, only a few megamouth sharks have been seen with 44 specimens known to have been caught or sighted as of 2009 and three recordings on film. Like the basking shark and whale shark, it is a filter feeder, and swims with its enormous mouth wide open, filtering water for plankton and jellyfish. It is distinctive for its large head with rubbery lips. It is so unlike any other type of shark that it is classified in its own family.
 Hammerhead Shark
The hammerhead sharks are a group of sharks so named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a “hammer” shape called a “cephalofoil”. The shark’s eyes and nostrils are at the tips of the extensions. The hammer shape of the head was thought to help sharks find food, aiding in close-quarters maneuverability and allowing the shark to turn sharply without losing stability. In late 2007 scientists discovered that hammerhead sharks can reproduce asexually through a rare method known as parthenogenesis (a direct development without the need of a sperm, similar to how social insects can reproduce). Of the nine known species of hammerhead, three can be dangerous to humans: the scalloped, great, and smooth hammerheads.
 Goblin Shark
The goblin shark is a deep-sea shark. Its most distinctive characteristic is the unorthodox 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. 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. As you can see from the image above, it is one of the most striking (and fearsome) looking sharks.

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