Reactive oxygen species (ROS) are supposed to play a major role in the aging process, thus the amount of generated ROS influences maximum lifespan of individuals. In air breathing animals, free radicals are generated during normal metabolism. In marine ectotherms metabolism largely depends on environmental temperature and individuals can experience large annual, monthly and also daily temperature variations, depending on their specific environment.Marine ectotherms from the Polar Regions generally show low metabolic rates at their low environmental temperatures. At lower temperatures, the lower metabolic rates and correspondingly lower reactive oxygen species propagation from aerobic mitochondrial activity may result in a slower rate of physiological ageing leading to longer maximum lifespan. Indeed it has been found that polar ectotherms exhibit longer maximum life spans compared to species from temperate or tropical environments. Hence, temperature affects the relationship between chronological age (i.e. absolute life time) and physiological age (i.e. a less clearly defined measure of physiological fitness), which are positively correlated, but not necessarily linearly and in the same way in each species. We investigated different bivalve species from polar and temperate environments to see whether theses animals age according to the free radical theory of aging and the theory could explain the longer maximum lifespan of the polar species. We found that polar bivalves not only show lower metabolism but also show lower free radical generation, higher antioxidant capacities and in line with this a slower decline in mitochondrial function and accumulation of oxidative damage products with age compared to temperate species. Marine bivalves are excellent model organisms for aging research as the individual age of each animals can be determined by age-ring counts of the shell. It is therefore possible to investigate how environmental factors influence the ageing process.