The cellular process of aging and the differences in maximum life span (MLSP) of related species can result from differences in cell functioning and structure deterioration, due to damage caused by incomplete reduced reactive oxygen derivatives {ROS} .Therefore, low antioxidative capacities and high levels of tissue damage can be expected in species with a short MLSP. Extrinsic factors like temperature are known to accelerate the rate of oxygen consumption which can contribute to the formation of ROS, causing oxidative damage. The catarina scallop Argopecten ventricosus is among the shortest-lived scallop species with a maximum life span of 2-3 years. Due to its short lifespan, this scallop is an ideal model to study how internal and environmental factors modulate the aging process.In this study, we measured superoxide-dismutase (SOD), catalase, protein carbonyls and lipid peroxidation in different organs (adductor muscle, mantle and gill) of 8 months old scallops cultivated in its natural habitat (Rancho Bueno BCS) and in the laboratory at the average temperature registered in this location (In situ temperature) and at In situ + 5 °C . Further, we determined the oxygen consumption as a measure of metabolic rate as well as the growth in the different treatments.Animals were obtained from a hatchery (genetically similar animals) and grown in the laboratory for 1 œ months to a size of 5 mm until the young animals were exposed to different experimental conditions in the laboratory and in the field. One part of the animals was raised in the laboratory under different temperature regimes: in situ field temperatures and in situ field temperatures with elevated max. 5°C. Another part of the population was reared directly in the field in nestier trays.The laboratory animals reared at in situ field temperatures as well as at elevated temperatures have higher levels of the antioxidant enzyme catalase than the animals growing in the nestier trays in the field. In all animals, the level of oxidation is higher in gill than in muscle and mantle tissues, showing the susceptibility of the gill to oxidative stress. The antioxidant superoxide dismutase is higher in the scallops being reared at elevated temperatures in the laboratory as well as in the field without differences between tissues (muscle, mantle and gill). Metabolic activity was measured after two days without food in order to eliminate the impact of specific dynamic action for the determination of the standard metabolic rate and again after feeding for the further determination of energy turnover and expenditure. The oxygen consumption after feeding was significantly higher in the laboratory animals in contrast to the field animals and the field treatments do not show significant differences in their metabolic rates after feeding. The levels of tissue damage (lipid peroxidation and protein carbonyls) are being analyzed and will be presented in the workshop in April.