Most model organisms for ageing, like rat and fruit fly, have to be reared in the laboratory for exact age determination. In contrast bivalves show age rings like trees, therefore the processes that modulate bivalve ageing in the natural environment can be investigated as it is possible to determine the age in years of each individual sampled from the wild.Reactive oxygen species (ROS) are assumed to play a major role in the ageing process. The investigation of changes in ROS generation, destruction and damaging action with age in bivalve species corroborated this assumption as a decline in mitochondrial function, oxidative capacity and an increase in oxidative damage was found in most investigated species.However in an inter-species comparison the amount and age related change in prooxidative and antioxidative parameters as well as in oxidative damage did not always correlate with the maximum lifespan (MLSP) of the different species. In short lived (MLSP 8-10years) swimming scallops ROS generation rate of isolated mantle mitochondria is close to detection limit while in longer living mud clams isolated mitochondria showed ROS generation rates up to 0.12 nmol H2O2 min-1 mg-1 mitochondrial protein. Further the scallop mitochondria showed only a minor decline in mitochondrial function (respiration, respiratory control ratio) with age compared to the mud clam. The question arises how and why the scallop species maintains mitochondrial function with age. To test the hypothesis that the species has to maintain physiological function until old age to escape predation we investigated the change in swimming activity and its causes on cellular homeostatis in different aged scallops. Results are currently calculated and will be presented.