(full paper is archived in the Miller Library)
Title: Limits and implications of thermal tolerance in the
limpet, Lottia digitalis
Student Author(s): Aiello, Linnea
Faculty Advisor(s): Denny, Mark
Location: Final papers biology 175H
Date: June 2004
Abstract: Of all organisms on Earth, invertebrates of the rocky intertidal zones experience some of the most extreme and varied environments, from near freezing seawater to hot, dry sunlight. Thus, these organisms experience an unusually large range of potentially lethal body temperatures. Lottia digitalis, a high intertidal limpet of the Pacific North American coast, is one such creature. What is the thermal tolerance of Lottia digitalis, and how often do they see these body temperatures?
The lethal temperature limits of L. digitalis were found, in air, to vary depending on length of exposure time. At ten minutes of heat exposure, limpet survivorship (tested 24 hours after exposure) declined from 100% to 0% as temperature increased from 41 to 45° Celsius. At three hours and forty minutes of exposure, a similarly steep decline was noted, but at a lower range of temperatures: from 37 to 40° C.
A heat-budget model was constructed to find how near L. digitalis live to their thermal maxima, and how often these maxima are exceeded. A heat budget is a mathematical model that predicts the body temperature of an organism, based on records of past environmental conditions plus physical characteristics of the organism. A comparison between the heat extremes predicted by the heat-budget model and the thermal limits showed that L. digitalis approaches within 5° C of its thermal limit once every 12 years (on average). L. digitalis do not live as close to their thermal limit as other intertidal organisms, but their preference for living on exposed rock surfaces may make them susceptible to an increase in climatic air temperature