Giant clam

Tridacna gigas, the giant clam (Tridacnidae), is the largest living bivalve, with shells typically 70–120 cm long and up to a recorded 137 cm, and live weights exceeding 200 kg and reaching about 340 kg. The heavy shell bears four or five broad radial folds; the exposed mantle carries hundreds to thousands of pinhole eyespots. It is restricted to Indo-Pacific coral reefs at 0–20 m. Symbiotic zooxanthellae supply roughly 65–70% of its energy. IUCN assessed it as Critically Endangered in 2024; it is in CITES Appendix II and is a first-class protected species in China.