Читать книгу Diving Indonesia Periplus Adventure Guid онлайн

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All bivalves must hold their shell halves at least slightly ajar to maintain water circulation through their bodies. But when danger threatens they are clamped shut. Some Indonesian bivalves gain further protection by boring into corals and reef rock, so that predators cannot reach them. The boring is achieved by a combination of chemical action and rasping with the two shell haves. Eventually, reef bivalves become so encrusted with sponges, coralline algae, bryozoans and cnidarians that they are barely visible.

Giant clams. The giant reef clams, Tridacna spp., have a different means of feeding. Like reef-building corals, Tridacna clams harbor zooxanthellae in their fleshy mantles, and can thus "manufacture" most—or perhaps all—of their own food. Like corals, they require lots of light, and tend to be found in the shallows. They grow with the hinge of their shells down, and their rippled gape facing the sun.

There are seven species of Tridacna, of which the giant clam, T. gigas, is the most dramatic. These animals can reach a meter and a half in diameter. An animal that big could be a century old. Although smaller than T gigas, T squamosa has a beautiful ruffled shell. The fleshy mantles of Tridacna clams are beautiful, varying in color from brown to yellow to green to blue, with contrasting spots or mottling.