Class: Polyplacophora

The Polyplacophora or chitons are a small class consisting entirely of marine species. Chitons are marine molluscs which are highly adapted to life in the intertidal zone. The shells of chitons are characteristically divided into 8 transverse, overlapping shell plates or valves. The foot is greatly expanded, forming a large flattened sole which is used not only for locomotion but also for maintaining firm contact with the rock surface. Adhesion is effected mainly by the foot under normal conditions but, when the animal is disturbed, the girdle (the soft part surrounding the shell) is also clamped down tightly onto the rock surface. Chitons feed on small particles of algae on the rock surface which are scraped off using the radula. Feeding normally takes place when covered by the tide, and they tend to be most active when immersed at night. They are normally inactive animals and move only to feed, but often show 'homing behaviour', which enables them to return to the same area of rock.