Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Distribution of the terrestrial isopod Alloniscus perconvexus on a sandy beach and factors affecting its range and population density
Student Author(s): Hainsworth, Barbara E.
Faculty Advisor(s): Lee, Welton
Pages: 33
Location: Final Papers Biology 175H
Date: June 1972
Keywords: sandy beaches
Abstract: The range and distribution of the beach isopod Allonsicus perconvexus was found to change over time. Compression and expansion of the range was observed to coincide with spring and neap tides, respectively. The upper limit of the distribution seemed to be set by moisture content of the sand, wheras extreme tidal height appeared to delimit the lower limits of the isopod's range. Range expansion and compression takes place by nighttime activity patterns. While the organism appears to be highly sensitive to the moisture content of the sand, and moves in direct relationship to moisture gradients, its activity can be modified by the presence of light, which inhibits all movement, and by a thigmotactic response which is often enhanced by the presence of potential food. Wave action and physical distrubance may reinforce those factors delineating its lower limit on the beach.