True Giant Clam

Tridacna gigas is known as the true giant clam and is the largest of all the giant clam species, growing to sizes over a meter wide and weights in excess of 496 pounds. 

The geographic range of T. gigas spans the shallow waters of the Indo-Pacific and the Great Barrier Reef, from Myanmar in the west to the Republic of Kiribati in the east, and from the Ryukyus Islands of Japan in the north to Queensland, Australia in the south. 

T. gigas is typically associated with coral reefs and can be found in many habitats, including high- and low-islands, atoll lagoons, and fringing reefs. Individuals are typically found between the depths of 6 to 65 feet, often among hard coral communities, hard reef substrata, or on bare sand.

T. gigas is readily identified by many characteristics, most notably its large size. Its shell is thick and heavy, with deep radial folds. Often, the mantle is yellowish-brown to olive-green and features numerous small, brilliant blue-green rings, which are especially prevalent along the lateral edges of the mantle. 

Decades of intense, unregulated harvest has driven T. gigas to very low abundance throughout much of its range. Past and ongoing harvest for meat and shells is the primary threat to this and other giant clam species.