Biodiversity in Littorina species (Mollusca: Gastropoda):: a physiological approach using heat-coma

The upper critical thermal limits were measured as heat-coma temperatures in Littorina species as a tool for examining physiological diversity. Thermal tolerance was found to be stable within a population, but extensive variation occurred between populations and species. All species examined displayed heat-coma values of similar to 30 degreesC and did not show a positive correlation with short height. Eulittoral-fringe species tended to have higher coma temperatures than eulittoral species. Coma temperatures varied both seasonally and geographically. Lethal thermal limits were also investigated; these were similar to 10 C degrees higher than coma temperatures.