Clams, like snails, nudibranchs, octopi, squid and cuttlefish, are mollusks. Bivalve mollusks include the clam, oyster, mussel and scallop. A bivalve mollusk is a soft-bodied animal enclosed within two shells which are hinged. The outer muscular flesh of the body covers the internal organs and is called the “mantle”. Clams move by way of a foot-like appendage that is distended from the shell. The mantle manufactures the shell of the clam by secretion.
The big brother (or sister) of the clam family is the giant clam of the family Tridecane. These inhabit most tropical oceans but the largest by far, tridacna gigas, is found in the Indo-Pacific ocean. These giant clams can be several feet in length (as well as width when the shell is open).
Your photograph is a close-up of the beautiful colors of the Indo-Pacific tridacna gigas clam mantle. The striking yellow, blue and green spots of colors are caused by the algae embedded in the mantle. Some clam species gain substantial nutritional benefit from the photosyn-thetic activity of the algae within the mantle. The openings in the mantle strain water for nutrients and expel waste.
Giant clams are not dangerous, per se, but they can close their monstrous shells fairly quickly. I know of one photographer who put his camera too far into the shell toward the mantle, causing the shells to close on his arm. The photographer had to be awfully patient until the clam decided to open its shell again.
This photograph of a giant clam mantle close-up was taken in 1991 at New Georgia Island, Solomon Islands with a Canon F-1, 100 mm macro lens and Kodachrome ISO 25 film.
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