Valve (chiton)

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Acanthopleura spinosa showing its eight valves and surrounding girdle.
Acanthopleura spinosa showing its eight valves and surrounding girdle.

Valves, when referring to Chitons, are eight dorsal, articulated shell plates, which are frequently brightly coloured and/or sculptured. These valves contain unique microscopic structures called aesthetes which appear to have both sensory and secretory functions.

Tonicella lineata illustrating the coloration possible in chitons.
Tonicella lineata illustrating the coloration possible in chitons.

The valves are embedded in a fleshy, muscular, flexible girdle which may bear calcareous scales or spicules and is sometimes highly coloured or patterned. The girdle and articulated valves allow the animal to curl up if it becomes detached.

Valves can also refer to the two shells in a bivalve mollusc.

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