Swimming of the sea cucumber Parastichopus californicus (stimpson) in response to sea stars

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 increase in the size of the holothurian. No satisfactory evidence is available for a predator-prey relationship between Parastichopus californicus and any of the sea stars tested, raising the question as to whether there is justification for terming this a true “escape response”.

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Notes on contributors

Abe S. Margolin

Deceased 28. October 1973