Availability of Drift Materials and the Covering Response of the Sea Urchin Strongylocentrotus purpuratus (Stimpson)

Individuals of Strongylocentrotus purpuratus (Stimpson) are found covered with a variety of debris. Algae and surf grass often are cover on the aboral surface and are eaten on the oral surface. Strongylocentrotus purpuratus individuals show no tendency to drop their cover at night and assume it again at daybreak. Individuals of this species are more extensively covered in areas of surge activity than they are in tidepools. The materials most frequently used for cover also differ in these two areas. The availability of drift materials is the most important factor in determining the extent of covering and the types of covering materials held by Strongylocentrotus purpuratus