Читать книгу Diving Indonesia Periplus Adventure Guid онлайн

90 страница из 170

The octopus has highly developed eyes and a very sophisticated nervous system. It is thus considered "intelligent," and people find it hard to believe that it is a mollusc. The white color of this specimen suggests exhaustion, and perhaps the photographer was a bit overzealous in getting this shot.

Trochus. Top shells (Trochus spp.) are relatively large (6-8 cm.), and conical. Before the advent of plastics they were widely collected for the manufacture of buttons. Removing the grubby outer layer of shell reveals the lustrous nacre, or mother-of-pearl beneath. Until the invention of Bakelite, and the many plastics that followed, shell nacre for buttons was an important business in Indonesia. Today they are still collected, most to be used in souvenirs and to supply the small market for "real" buttons.

Clams and Oysters

The bivalves include such familiar forms as clams, oysters, mussels and scallops. All have two articulated shell halves that can be closed with a large muscle. It is this muscle that makes bivalves so prized as seafood. With a very few exceptions, bivalves cannot move, like gastropods, and thus most have adapted to filter-feeding. They draw water in through one tube or "siphon" and pass it out through another. This stream of water passes through the animal's gills, which serve the dual purpose of respiration and filtering out food particles.