Giant clam

From Freepedia

In Japanese Cuisine, Geoduck (mirugai) is sometimes referred to as "Giant clam".

Giant Clam
Conservation status: Vulnerable

Scientific classification

Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Veneroida
Family:	Tridacnidae
Genus:	Tridacna
Species:	gigas

Binomial name

Tridacna gigas
Linnaeus, 1758

Image:Giant clam detail.jpg

The Giant Clam (Tridacna gigas) or traditionally, pa’ua, is the largest living bivalve mollusc. One of a number of large clam species native to the shallow coral reefs of the South Pacific and Indian oceans, they weigh an average of 440 pounds and can measure as much as 1.5 meters across.

Permanently sessile in adulthood, the creature's siphon and mantle tissues act as a habitat for the green algae on which it feeds. By day, its shell remains open unless disturbed, and in this way the symbiotic algae may receive sunlight they need to grow.

History

As is often the case with uncharacteristically large species, the giant clam has been historically misunderstood. Even reputable scientific and technical manuals once claimed that the great mollusk had caused deaths. In those days the Giant clam was also known as killer clam or man-eating clam. Versions of the U.S. Navy Diving Manual even gave detailed instructions for releasing oneself from its grasp by severing the adductor muscles used to close its shell.

Image:Giant clam with diver.jpg

Today, it is generally acknowledged that the giant clam is neither aggressive nor particularly dangerous; while it is certainly capable of holding one fast in its grip, the shell's closing action is actually a defensive response, and far too slow to pose any reasonable threat. No account of a human being trapped in this manner has ever been substantiated.

Conservation status

The IUCN lists the giant clams as vulnerable. There is concern among conservationists for the sustainability of practices among those who use the animal as a source of livelihood. The numbers in the wild have been greatly reduced by extensive harvesting for food and aquarium trade. Illegal trade in giant clam shells for use as decorative accoutrements abounds, and the meat, called Himejako in Japan, is prized as a delicacy.