The largest of all mollusks, the giant clam is an important part of most of the coral reefs of the South Pacific and Indian oceans. These ancient creatures of the seas have been thought to have evolved over 65 million years along with modern species of coral.
Giant clams are capable of reaching 4 feet (1.2 meters) in length and weighing more than 500 pounds (227 kg). They also have a long lifespan of 100 or more. Some marine biologists even believe that some of the larger ones that have been found off the East Coast of the U.S. are over 200 years old. And did you know that no two giant clams have the same coloration. So how do they get that big?
Just like some coral species, giant clams share a symbiotic relationship with millions of single cell dinoflagellate algae called ‘zooxanthellae’. They consume the sugars and proteins produced by the billions of algae that live in their tissues; in exchange, they offer the algae a safe home and regular access to sunlight for photosynthesis, basking by day below the water’s surface with their fluted shells open and their multi-colored mantles exposed. They also get nutrients by siphoning up and filter feeding on passing plankton.
This huge shellfish, is often been misunderstood in history and were once labeled the killer clam or man-eating clam! However, the clam is not aggressive at all and while it is certainly capable of gripping a person, the shell’s closing action is too slowly to pose a serious threat. So all those stories of divers or fisher folk drowning because of giant clams
latching on to their arms with malicious intents were all discredited to be false. The presence of Giant Clams are actually an indication of a healthy coral reef. These creatures are highly sensitive to changes in the water acidity and temperature and perish where conditions are less than perfect. They also play a very important role in the reef as they act as nurseries for a host of fish and invertebrates as well as shrimp. Clam shells even provide the perfect substrates for attachment for several species of sponges, coral and algae which promote the development of the reef.
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