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Southwest Florida Shells with Emphasis on Sanibel & Captiva

By José H. Leal

Family Acanthochitonidae

Acanthochitona pygmaea

(Pilsbry, 1893)

Striate Glass-hair Chiton

Chitons belong to a class of mollusks named the Polyplacophora (Greek for "bearers of many plates"). The chiton shell is divided into eight (rarely seven) plates, or valves. The valves are interlocked, and are surrounded by a tissue called the girdle. The Striate Glass-hair Chiton, Acanthochitona pygmaea (Pilsbry, 1893), is one of the two species of chitons found locally in shallow-water. It may reach a little more than 13 mm (about 0.5 inch) in size. The triangular central area of the valves shows longitudinal lines, with the lateral areas sprinkled with minute beads. The valves are partially covered by a very broad girdle. The girdle has two rows of tufts of glass-like bristles, each tuft resembling a minute bottle brush. The color is very variable; valves may be green, red, orange, or with many combinations of these colors. Do not confuse with the more common local chiton species, the similar-sized Eastern Beaded Chiton, Chaetopleura apiculata, which has a very narrow girdle minimally covering the shell valves. The chiton illustrated was found by José H. Leal on Bunche Beach (Fort Myers) on March 22, 2017 crawling on a Sunray Venus shell.