A comparative analysis of plasticity of thermal limits in porcelain crabs across latitudinal and intertidal zone clines

The effect of thermal acclimation on cardiac thermal performance limits was examined in congeneric species of porcelain crabs (genus Petrolisthes) from temperate and subtropical habitats. In vivo heart rate was monitored using impedance electrodes during thermal ramps (0.1 8C/min) where temperature either increased or decreased from an intermediate temperature to thermal extremes. Arrhenius plots were used to define upper and lower critical temperatures of cardiac function (CTmax and CTmin, respectively). Across species and acclimation conditions, CTmax ranged from approximately 28.4 to 41.7 8C and CTmin from approximately 1.3 to 11.3 8C. Thermal acclimation had the greatest effect on CTmax in species from the coolest thermal microhabitat and the smallest effect on CTmax in species from the hottest thermal microhabitat. The opposite effect was observed on CTmin. The ecological consequences of these results are counterintuitive, as the most heat-tolerant species are predicted to be most susceptible to global warming. The results of this study will form the foundation of future studies designed to elucidate the mechanistic bases of thermal plasticity and eurythermy in porcelain crabs. D 2004 Elsevier B.V. All rights reserved.