An analysis of heat and desiccation stresses as critical environmental factors on a rocky shore

Abstract

In an attempt to understand the factors which were important in inducing mortality in limpets on a rocky shore on the west coast of Rottnest Island, Western Australia, tests were conducted on four species of limpets with regard to desiccation tolerance, survival and body temperature profiles during intense insolation. These results were compared against field measurements of body and substratum temperature, and body water content. Interspecific differences in tolerance of desiccation was not correlated to vertical zonation patterns, and lethal body water contents were much lower than field body water contents in all four species, suggesting that desiccation was not an operational mortality factor. Death was induced experimentally under intense insolation in all species, but Collisella onychitis showed better tolerance of high body temperature than Patelloida alticostata, Siphonaria kurracheensis and S. zelandica. Under such rapid rates of heating, death occurred when body temperature (measured at the mantle-foot margin) approached field maxima for the two species of Siphonaria. The results indicated that desiccation during insolation stress was not a significant mortality factor for these four species. However even brief periods of intense heating, as can occur during periods of hot, sunny and calm days, could become critical.