(full paper is archived in the Miller Library)
Title: The effects of heat stress on the intertidal size gradient of Tegula funebralis
Student Author(s): Taylor, Shannon
Faculty Advisor(s): Somero, George
Location: Final Papers Biology 175H
Date: June 2000
Abstract: Tegula funebralis, the black turban snail, is an intertidal gastropod with a distinctive intertidal size gradient; large snails tend to live in the lower portion of the snail's range and small snails in the upper portion. Many factors have been suggested to explain this phenomenon, including differential larval settlement, juvenile mortality, response to light, and, most commonly, predation pressure. I investigated the potential contribution of thermal stress on size gradient in a study area that has been shown to have very little predation on Tegula. I performed two types of experiments: temperature measurements of gelatin-filled snails and heat shock protein analysis of gill tissue from large and small snails that had been caged in the intertidal. Although my heat shock analysis was inconclusive, temperatures were consistently lower in small snails than in large snails, both in a controlled environment and in the field, a disparity possible caused by differences in the absorptivity of large and small snail shells. Heat shock protein analysis could verify that larger snails experience this increased heat stress. Finally, a vertical size gradient also appears to occur between different intertidal gastropod species, another indication that size-dependent thermal stress could be important in determining intertidal gastropod zonation.