Gastropod Defensive Responses and Their Effectiveness in Reducing Predation by Starfishes

Abstract

Numerous Monterey Bay gastropods show marked escape responses on contact with, or in the presence of Pisaster ochraceus, P. giganteus, and Pycnopodia helianthoides. These organisms are not taken for food by P. ochraceus in proportion to their abundance and availability, indicating that the escape reaction is to a certain extent protective. Acmaea scabra generally does not respond to contact by sea stars. The fact that it is the limpet most frequently used as food by P. ochraceus may be the result of lack of this response. The active agent responsible for gastropod responses is mainly associated with the epithelial covering of the water vascular system. The gastropod response mechanism is not totally effective, and gastropods tend to become nonreactive following continual contact or presence of a predatory sea star.