(full paper is archived in the Miller Library)
Title: Distribution and movement of the gastropod Tricolia pulloides on the intertidal alga Gigartina papillata
Student Author(s): Foster, Wm. Kelly
Location: Final Papers Biology 175H
Date: June 1979
Keywords: midtide forest community
Abstract: In all experiments, Tricolia pulloides populations shifted to outer regions of Gigartina papillata during optimum conditions of calm submersion in dim light. Desiccation is a considerable threat to Tricolia pulloides: an LD50 of 18 hours was reported for laboratory exposure (Firestone, 1979 unpublished Hopkins ms), and may be considerably less in bright sunlight. Thus, negative phototaxis seen in natural and artificial surroundings would seem an adaptive response. Inward movement of T. pulloides during strong surge minimizes the threat of being swept off the alga, since inner regions swing through a smaller arc and with less tangential velocity than frond ends. During trial surge experiments snails on outer areas of algae often were swept off if strong manual surge was begun suddenly. Thus, inward movement of T. pulloides populations during surge also appears to be an adaptive response.