Giant Clam

Giant Clams (Tridacna gigas) are the largest living bivalve molluscs. A pair of shells can reach a weight of 260 kg and a length of 1.4 metres. Giant Clams live in shallow water on coral reefs. They rest with their shells partially open, so that their body tissues are exposed to light. Giant Clams farm colonies of microscopic organisms (zooxanthellae) in the tissues that line their shells. They also have lense-like organs in their outer skin (mantle) which allows sunlight to reach the zooxanthellae. These organisms provide some of the nutrients needed by the clam to survive. Stories of Giant Clams clamping down on the arm or leg of an unwary diver are far-fetched. This is not possible, as Giant Clams can only close their shells slowly.