Giant clam

Animal Facts

  • Scientific Name

    Tridacna sp

  • Animal Type


  • Diet

    sugars and proteins produced by the algae living inside their tissues; tiny, drifting plants and animals filtered from the water

  • Size

    the largest species, Tridacna gigas, can grow to 4.25 feet (1.3 m) long

  • Relatives

    other clams and mussels, scallops, oysters; Phylum: Mollusca; Class: Bivalvia

  • Habitat

    Coral Reefs

  • Range

    Western Pacific coral reefs, Indian Ocean and the Red Sea

Natural History

Like corals, giant clams live in partnership with tiny plantlike algae (called zooxanthellae) that live inside the clams' tissues. And as with corals, the arrangement helps both creatures. The algae gain protection from grazing animals; the clams grow large with the benefit of food produced by the algae. 

At home on reefs throughout the Indian Ocean, the South Pacific and parts of South Africa, giant clams live on shallow reef flats down to depths of around 66 feet (20 m). Below that, the algae they depend on to survive wouldn't have enough sunlight to grow.


The giant clam, Tridacna gigas, is rare due to overharvesting by people. Giant clams are now being farmed, which can cut down on the numbers taken from the wild.

Cool Facts

As their name implies, giant clams are the largest clams in the world. The largest grow more than four feet (1.2 m) long. 

Once a giant clam settles into a place and begins to grow, it stays permanently attached to that spot for life.

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