Giant clams are a family (Tridacninae) of bivalves within the Mollusca phylum. Their geographical ranges span across the Indo-Pacific to Africa, generally living in shallow to moderate reef zones. In total, there are twelve species of giant clams globally, from two genera:
One species considered the ‘true giant clam’ is the Tridacna gigas, the largest known bivalve to have ever existed. They can grow on the reef, on rubble or in the sand.
Contrastingly, the smallest species of giant clam is the Tridacna crocea, which reaches up to around 20 cm in size, and bores into hard substrate such as rocks and corals as it grows, so that only it’s upper shell and mantle isvisible. This habitat provides the smaller T. crocea with some shelter from predation.