Posted : December 2008
Author : Sam
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.
This distinctively-marked shark is the only member of its
genus Rhincodon and its family, Rhincodontidae (called Rhinodontes before
1984), which is grouped into the subclass Elasmobranchii in the class
Chondrichthyes.
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".
In Mexico,
and throughout much of Latin America, the
whale shark is known as "pez dama" or "domino" for its
patterns of spots. Whales sharks go by the name of "Sapodilla Tom" in
Belize
due to the regularity of sightings near the Sapodilla Cayes on the Belize Barrier
Reef. In Africa, the names for the whale shark are very evocative: "Papa
Shillingi" in Kenya
came about as it is believed that God threw shillings upon the shark which are
now its spots, and in Madagascar
whale sharks are known locally as "Marokintana" which means
"Many stars". In Indonesia,
Javanese also called this species referring to star as "geger
lintang" which has meaning "stars in the back".
The whale shark is a filter feeder - one of only three known
filter feeding shark species (along with the basking shark and the megamouth
shark). It feeds on phytoplankton, macro-algae, plankton, krill and small
nektonic life, such as small squid or vertebrates. The many rows of teeth play
no role in feeding; in fact, they are reduced in size in the whale shark.
Instead, the shark sucks in a mouthful of water, closes its mouth and expels
the water through its gills.
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.
~Blog Admin~
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