chiton

Chitons are marine mollusks in the class Polyplacophora. They have a dorsoventrally flattened body and a shell composed of eight articulating calcareous plates that can slide relative to each other. The plates are arranged in a single row along the back and are partially embedded in a tough, movable mantle girdle that surrounds the animal. A broad, muscular foot is used for creeping and strong adhesion to hard substrates such as rocks.

Anatomy and feeding: chitons lack a conspicuous head and have a radula, a ribbon-like structure with rows of teeth, used to scrape algae from rock surfaces. The mantle secretes the shell plates, and many species bear eyes or light-detecting organs along the girdle. Some chitons show regional variation in plate size and ornamentation, aiding camouflage and protection.

Habitat and ecology: chitons occur worldwide in shallow to moderately deep marine waters, but most are associated with rocky shores, tidal pools, and coral reefs. They cling tightly to substrates in strong waves, grazing on algae and biofilm. Their slow movements and durable plate armor help them survive splash and desiccation in intertidal zones.

Reproduction and development: most chitons are dioecious, releasing eggs and sperm into the water for external fertilization. Fertilized eggs hatch into free-swimming larvae, typically trochophore and later veliger stages, before metamorphosing into juvenile chitons with eight plates.

Taxonomy and naming: the name chiton derives from the Greek chiton meaning tunic or coat, referring to the animal’s protective shell.