Behaviour
P. chilensis occurs in the rocky intertidal zone in temperate seas off the coast of Chile. It is mainly present in the lower algal zone, dominated by the kelps Lessonia nigrescens and Durvillaea antarctica and various encrusting coralline algae. Echinoids occurring in this zone include Loxechinus albus and Tetrapygus niger, and starfish include Stichaster striatus, Meyenaster gelatinosus and the dominant Heliaster helianthus. These starfish are the dominant carnivores in this zone and seem to play an important role in maintaining the community structure. Besides being a predator of sessile organisms, P. chilensis is an opportunistic feeder, scavenging for dead animal matter and detritus. It is a small species, and avoids being preyed on by the larger starfish by tending to remain in concealed locations.