Thursday, December 25, 2008

Whale Shark - The Worlds Biggest Fish!

The whale shark, Rhincodon typus, is a slow moving filter feeding shark that is the largest living fish species. It can grow up to 12.2 m. (40 ft.) in length and can weigh up to 13.6 tonnes (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.






The species was first identified in April 1828 following the harpooning of a 4.6-metre (15.1 ft) specimen in Table Bay, South Africa. It was described the following year by Andrew Smith, a military doctor associated with British troops stationed in Cape Town. He proceeded to publish a more detailed description of the species in 1849. The name "whale shark" comes from the fish's physiology; that is, a shark as large as a whale that shares a similar filter feeder eating mode. Known as a deity in a Vietnamese religion, the whale shark is called "Ca Ong", which literally translates as "Sir Fish".








During the slight delay between closing the mouth and opening the gill flaps, plankton is trapped against the dermal denticles which line its gill plates and pharynx. This fine sieve-like apparatus, which is a unique modification of the gill rakers, prevents the passage of anything but fluid out through the gills (anything above 2 to 3 mm in diameter is trapped). Any material caught in the filter between the gill bars is swallowed. Whale sharks have been observed "coughing" and it is presumed that this is a method of clearing a build up of food particles in the gill rakers



Whale sharks congregate at reefs off the Belizean Caribbean coast, supplementing their ordinary diet by feeding on the spawn of giant cubera snappers, which spawn in these waters between the full and new moons of March through September.

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