Which living bivalve is the world's largest?

The giant clam, Tridacna gigas, is the world's largest living bivalve.

It can grow to more than 1.2 metres long and weigh over 200 kilograms. Its massive shell has deep folds, while the exposed mantle displays striking colours created by pigments and symbiotic algae living within its tissues.

Like other bivalves, a giant clam has two shell valves joined by a hinge. Unlike many shellfish, it gains much of its energy from photosynthetic algae, although it also filters small food particles from seawater. It lives in shallow tropical Indo-Pacific reefs.

The giant clam is not the same as a geoduck, which is famous for its long siphon, or the much smaller Pacific oyster. Giant clams are generally harmless to divers and do not snap shut with enough force to trap a person, despite an enduring popular myth.