Chitons

Archerd Shell Collection > Shell Classes > Polyplacophora

Polyplacophora (Chiton) Page

Description:: About 800 existing species of chiton are identified. All are rock-dwelling marine molluscs with oval shaped bodies that are flattened from back to front (dorsoventrally). Eight overlapping and separate plates form the shell, and the plates are articulated by a fairly complex set of muscles. The class is designated from its name, Polyplacophora, which means "bearer of many plates."; Chitons are mainly found in shallow water, often under rocks and other shells, but several genera can be found in water as deep as 5,000 ft.. They become active at twilight and move around very slowly in search of food. Most are grazers, and with a multi-toothed radula, they can feed on small algae and other tiny organisms. Some are actively carnivorous, feeding on small crustaceans by smothering them with the girdle; e.g., Lepidochitona.; The anatomy of chitons is comparatively simple, and with no evidence of torsion. Nevertheless, despite a primitive nervous system, chitons in the subfamily Toniciinae (Tonicia and Acanthopleura) possess rather remarkable eyes. They are found in shallow, tropical waters. Most other chitons, and those in the Ischnochitonidae family, do not have developed eyes, although they may respond to light. Most seem to depend on tactile or chemically sensitive nerve endings to locate food.; Interestingly, aboriginal Australians are known to have roasted and eaten Acanthopleura, while aboriginal Bermudan islanders also harvested chitons to make a soup (Beesley et al., 1998). Today, they have no commercial usefulness.