Giant clam
Depth: 15 m · Sunlight Zone
The giant clam is the biggest clam in the world and can grow over a meter wide and live more than a hundred years. Tiny algae live in its colorful mantle, making food from sunlight and helping to feed the clam. That is why it lives in shallow, sunny reefs. It closes only very slowly.
For scientists
The giant clam (Tridacna gigas) lives in symbiosis with zooxanthellae, photosynthetic algae in its vividly colored mantle tissue that cover much of its food needs; this is why it depends on clear, sunlit shallow water. It is the largest living bivalve, lives over a hundred years, and is a protandric hermaphrodite. Contrary to legend, it closes its shells far too slowly to be a danger to divers.
Source: Smithsonian Ocean
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