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Tropical Diver

Giant clam

Giant clam

(Tridacna gigas)

The giant clam is found in the southern and western Pacific and Indian Oceans. It inhabits shallow-water reef flats to depths of about 66 feet. This is the largest clam in the world. It can grow over four feet wide and weigh as much as 500 lbs. Once it has established itself at a location on the bottom, it remains there for life, which can be as long 100 years.

Contrary to its depiction in movies, the giant clam cannot quickly close its shell and trap the foot of an unwary diver. It will close its shell slowly in response to threats it can detect with special motion-sensing tissues in its skin.

See if you can locate the giant clam in the large reef exhibit in the Tropical Diver gallery.

Fun Facts

  • The giant clam lives in a symbiotic relationship with microalgae that are embedded in its tissues. The algae provide food for the clam.
  • These symbiotic algae are called “zooxanthellae”.
  • Due to this relationship, the giant clam must live in shallow, sunlit water so that the algae can photosynthesize.
  • The microscopic larvae of this clam drift with plankton for about ten days before settling to the bottom and attaching itself to a suitable hard surface.
  • The adult clam consumes plankton that it filters from the surrounding ocean water.
  • Download full fact sheet

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