Temperature Effects on Mitochondria from Hydrothermal Vent Invertebrates: Evidence for Adaptation to Elevated and Variable Habitat Temperatures

Abstract

The effects of elevated temperatures on mitochondrial respiration and the activities of selected mitochondrial enzymes were measured for several invertebrates endemic to the deep-sea hydrothermal vents to determine whether the differences in distribution patterns noted among these species are related to differences in temperature adaptation. Parallel studies were done with related (congeneric or confamilial) species from shallow marine habitats. Mitochondrial respiration of hydrothermal vent species living in zones with high water flux (high, variable temperatures), including the large tube worm Riftia pachyptila, the Pompeii worm Alvinella pompejana, and the brachyuran crab Bythograea thermydron, was more resistant to high temperatures than was mitochondrial respiration of hydrothermal vent species or shallow-living species in cooler waters, for example, the vent clam Calyptogena magnifica and mussel Bathymodiolus thermophilus. The temperatures at which Arrhenius plots of respiration rate exhibited sharp breaks were correlated with the apparent maximal habitat temperature of the species. The apparent Arrhenius activation energies of respiration also correlated with maximal habitat temperature, although not as closely as the Arrhenius break temperatures. Temperature inactivation of mitochondrial enzymes generally adhered to the pattern noted in the interspecific comparisons of mitochondrial respiration. These findings suggest that diferences in thermal adaptation exist among endemic vent species and that these differences are correlated with the microhabitat conditions the diferent species encounter at the vent sites.