Gary Bell/ Oceanwide / Giant Clam (Tridacna sp) mantle, Great Barrier Reef, Australia

Georgette Douwma / Pattern on mantle of Giant clam (Tridacna gigas). West Papua, Indonesia. Indo-West Pacific.

Richard Robinson / Giant Clam (Tridacna sp.) at North Minerva Reef / Teleki Tokelau a disputed territory in the South Pacific between Tonga and Fiji.

Richard Robinson / Giant Clam (Tridacna sp.) at North Minerva Reef / Teleki Tokelau a disputed territory in the South Pacific between Tonga and Fiji.

Richard Robinson / Giant Clam (Tridacna sp.) at North Minerva Reef / Teleki Tokelau a disputed territory in the South Pacific between Tonga and Fiji. January.

Jordi Chias / Table coral (Acropora) with Giant clams (Tridacna gigas) Addu Atoll, Maldives, Indian Ocean.

Linda Pitkin / Giant Clam, siphon (Tridacna sp.) Sangeang, off Sumbawa, Indonesia.

Pete Oxford / Giant Clam (Tridacna gigas), Cenderawasih Bay, West Papua, Indonesia

Pete Oxford / Giant Clam (Tridacna gigas), Cenderawasih Bay, West Papua, Indonesia

Georgette Douwma / Maxima giant clam (Tridacna maxima) Similan Islands, Andaman Sea, Thailand.

Georgette Douwma / Detail of mantle of Giant giant clam (Tridacna gigas) Colours come from symbiotic zooxanthellae in tissue,. Indonesia.

Georgette Douwma / Detail of mantle of Giant giant clam (Tridacna gigas) Colours come from symbiotic zooxanthellae in tissue,. Indonesia.