Solaster

Abstract: Seven asteroid species common to the northern California coast were studied for their defensive responses to the predator Solaster dawsoni. The presence or absence of an escape response was used to predict whether or not these species were susceptible to predation from Solaster. Strong escape responses were displayed by Patiria miniata, Henricia leviuscula, Leptasterias hexactis, Pycnopodia helianthoides, and small Pisaster ochraceus. Subsequent capture and consumption of Patiria, Henricia, Leptasterias and small P. ochraceus were observed. Solaster attacked all Pisaster spp. tested, but Pisaster brevispinus and larger P. ochraceus protected themselves from predation by utilizing their pedicellariae against Solaster whenever contact occurred. Dermasterias imbricata appeared to be immune to predation by Solaster. Contact between these two asteroids failed to elicit a defensive response in the former or an attack by the latter asteroid.

Abstract: Parastichopus californicus (Stimpson) displays a degree of activity which is in strong contrast to its usual lethargic habits, when it is contacted by certain species of sea stars. This active response begins with local contraction and crawling, accompanied by bending of the body, and culminates with active swimming, in which the animal moves freely and vigorously through the water in an undulating manner. All of sixteen species of sea stars tested produced at least some response, but onlv Pvcnopodia helianthoides, three species of the genus Solaster, Luidia foliolata, and Dermasterias imbricata produced a swimming reaction in an appreciable percentage of the trials; Pycnopodia always caused a swimming response. Actual contact appeared to be necessary to evoke the response. Repeated stimulation of the same individual gave no evidence of adaption on the part of the cucumber. Continuous stimulation produced swimming and crawling for 37 to 40 minutes, with final exhaustion accompanied by a temporary...