Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Prey species, their escape responses, and factors influencing micro-habitat distribution of Leptasterias hexactis
Student Author(s): Begle, Douglas P.
Faculty Advisor(s): Baxter, Chuck
Pages: 23
Location: Final Papers Biology 175H
Date: June 1979
Keywords: midtide forest community
Abstract: Leptasterias hexactis (Stimpson 1862) shows a patchy distribution along the rocky intertidal of south Monterey Bay. It was found that the population density increased linearly with an increasing amount of available shelter. Starfish are found either under rocks or algal thalli, due mainly to a strong negative phototaxis. Possible major factors behind this phototaxis are visual predation and dessication, and observations suggest that visual predation is primary. Leptasterias in shaded conditions tolerates exposure at low tide where there are no avian predators. The population at Pt. Pinos exhibits a high level of cryptic coloration which is proposed to result from visual predation. In the Hopkins Marine Station preserve, where populations of predators were highest, the stars occur in very low density. Food items of Leptasterias were examined at Pt. Pinos and under the Cannery and were found to be radically different both from each other and from previous work done in Puget Sound. In addition, escape responses were described for six local gastropods in the presence of Leptasterias. Tricolia pulloides showed the strongest response, with Mitrella tuberosa and Littorina scutulata exhibiting moderate responses. Barleeia haliotiphia and L. planaxis showed weak responses, and Bittium eschrichtii showed virtually no response to either chemoreception or contact with a starfish tube foot, even though Barleeia and Bittium are important food items.