Bivalves show age rings like trees, thus in contrast to other model organisms for ageing like rats or fruit flies which have to be reared in the laboratory to know the age, we can investigate the natural aging process as we can determine the age of each bivalve we catch from the wild. Mitochondria are supposed to play a major role in the aging process as they supply energy for maintenance and repair but also produce reactive oxygen (ROS) species which can lead to damage and disturbance of cellular structures and processes. We measured mitochondrial respiration and ROS generation in mitochondria as well as antioxidant capacities and oxidative tissue damage of various bivalve species with different maximum life spans and of different lifestyle (burrowing-swimming). The results show a decrease of mitochondrial respiration with age in all investigated species. The magnitude of the decrease generally correlated with the amount of generated ROS but not always with the lifespan of the different species. The results implicate that different lifestyles lead to mitochondrial adaptations which alter mitochondrial ROS generation. Factors influencing the aging process leading to different maximum life spans are discussed.