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

The upper critical thermal limits were measured as heat-coma temperatures i n Littorina species as a tool for examining physiological diversity. Therma l tolerance was found to be stable within a population, but extensive varia tion occurred between populations and species. All species examined display ed heat-coma values of similar to 30 degreesC and did not show a positive c orrelation with short height. Eulittoral-fringe species tended to have high er coma temperatures than eulittoral species. Coma temperatures varied both seasonally and geographically. Lethal thermal limits were also investigate d; these were similar to 10 C degrees higher than coma temperatures.