Giant clam

species of clam

The giant clams are the members of the clam genus Tridacna that are the largest living bivalve mollusks. There are actually several species of "giant clams" in the genus Tridacna, which are often misidentified for Tridacna gigas, the most commonly intended species referred to as “the giant clam”.

Giant clam
Giant clam or Tridacna gigas.jpg
A live individual of Tridacna gigas, with the mantle showing (Great Barrier Reef, Australia)
Scientific classification e
Unrecognized taxon (fix): Tridacna
Species:
Binomial name
Tridacna gigas
Synonyms[2]

Chama gigantea Perry, 1811

Mantle of giant clam with light-sensitive spots which detect danger and cause the clam to close

Tridacna gigas is one of the most endangered clam species. Antonio Pigafetta documented these in his journal as early as 1521. One of a number of large clam species native to the shallow coral reefs of the South Pacific and Indian oceans, they can weigh more than 200 kilograms (440 lb), measure as much as 120 cm (47 in) across and have an average lifespan in the wild of over 100 years.[3] They are also found off the shores of the Philippines and in the South China Sea in the coral reefs of Sabah (Malaysian Borneo).

The giant clam lives in flat coral sand or broken coral and can be found at depths of as much as 20 m (66 ft).[4] Its range covers the Indo-Pacific, but populations are diminishing quickly, and the giant clam has become extinct in many areas where it was once common. The maxima clam is found most commonly among giant clam species; it can be found off high- or low-elevation islands, in lagoons or fringing reefs. Its rapid growth rate is likely due to its ability to grow algae in its body tissue.[4]

A diver among many giant clams for scale.

Although larval clams are planktonic, they become sessile in adulthood. The creature's mantle tissues act as a home for the symbiotic single-celled dinoflagellate algae (zooxanthellae) from which the adult clams get most of their food. By day, the clam opens its shell and extends its mantle tissue so that the algae get the sunlight they need to photosynthesize.

  1. Wells, S. (1996). Tridacna gigas. The IUCN Red List of Threatened Species doi:10.2305/IUCN.UK.1996.RLTS.T22137A9362283.en
  2. Bouchet, P.; Huber, M. (2013). "Tridacna gigas (Linnaeus, 1758)". WoRMS. World Register of Marine Species. Retrieved 2014-04-09.
  3. "Giant Clam: Tridacna gigas". National Geographic Society. Archived from the original on 15 April 2012. Retrieved 2 June 2007.
  4. 4.0 4.1 Knop, p. 10.