Description: Predation is known to impact growth and reproduction, and the physiological state of the prey, including its susceptibility to oxidative stress. In this study, we investigated how prolonged exposure to predators modulates tissue specific antioxidant defense and oxidative damage in the short-lived epibenthic scallop Argopecten ventricosus (2 years maximum lifespan). Scallops that were experimentally exposed to predators had not only lower antioxidant capacities (superoxide dismutase and catalase), but also lower oxidative damage (protein carbonyls and TBARS = thiobarbituric acid reactive substances including lipid peroxides) in gills and mantle compared to individuals not exposed to predators. In contrast, oxidative damage in the swimming muscle was higher in predator-exposed scallops. When predator-exposed scallops were on the verge of spawning, levels of oxidative damage increased in gills and mantle in spite of a parallel increase in antioxidant defense in both tissues. Levels of oxidative damage increased also in the swimming muscle whereas muscle antioxidant capacities decreased. Interestingly, post-spawned scallops restored antioxidant capacities and oxidative damage to immature levels, suggesting they can recover from spawning-related oxidative stress. Our results show that predator exposure and gametogenesis modulate oxidative damage in a tissue specific manner and that high antioxidant capacities do not necessarily coincide with low oxidative damage.

Description: Increase in oxidative damage and decrease in cellular maintenance is often associated with aging, but, in marine ectotherms, both processes are also strongly influenced by somatic growth, maturation and reproduction. In this study, we used a single cohort of the short-lived catarina scallop Argopecten ventricosus, to investigate the effects of somatic growth, reproduction and aging on oxidative damage parameters (protein carbonyls, TBARS and lipofuscin) and cellular maintenance mechanisms (antioxidant activity and apoptosis) in scallops, caged in their natural environment. The concentrations of protein carbonyls and TBARS increased steeply during the early period of fast growth and during reproduction in one-year-old scallops. However, oxidative damage was transient, and apoptotic cell death played a pivotal role in eliminating damage in gill, mantle and muscle tissues of young scallops. Animals were able to reproduce again in the second year, but the reduced intensity of apoptosis impaired subsequent removal of damaged cells. Fast accumulation of the age pigment lipofuscin was observed in late survivors. Reproduction had a temperature independent effect on oxygen uptake and on oxidative stress markers in first year scallops. Compared to longer-lived bivalves, A. ventricosus seems more susceptible to oxidative stress with higher tissue-specific protein carbonyl levels and fast accumulation of lipofuscin in animals surviving the first and second spawning. Superoxide dismutase activity and apoptotic cell death intensity were higher in this short-lived scallop than in longer-lived bivalves. The life strategy of this short-lived and intensely predated scallop supports rapid somatic growth and fitness as well as early maturation at young age over cellular maintenance in second year scallops.

Description: The catarina scallop Argopecten ventricosus,is among the shortest-lived scallop species. It reaches market size within a year and is of high commercial value, (Maeda-Martínez et al. 2000). Due to its very short lifespan of only 2-3 y, this scallop is an ideal model to study how internal and environmentally factors modulate growth and aging. In our study we are testing the effect of one abiotic physical factor: elevated temperature and of the biotic stressor predation on growth and physiological aging of the catarina clam of the pacific coast of Baja California Sur, Mexico. 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 is being raised in the laboratory under different temperature regimes: in situ field temperatures and in situ field temperatures but elevated max. 5°C. Another part of the animals is reared directly in the field inside the sea grass as well as nestier trays (predator protected area) and outside sea grass (predator exposed area). The growth, metabolic rate and biochemical parameters are being analyzed in all different experimental groups over a time frame of two years to evaluate the physiological adaptations to the different environments conditions and experimental stressors. Scallops in the field grew more rapidly than animals maintained in the laboratory. The mean growth was 0.5 mm/day for the laboratory animals, compared to 2.3 mm/day for field animals. Animals grown at 5°C higher temperature in the Lab grew 4% slower than animals at in situ temperatures. Currently the measurements of metabolic rate and of scope of growth are carried out to determine the energetic balance and expenditure in the different treatments. Tissue antioxidant capacities and the activity of antioxidant enzymes are being measured. First results of the field animals before and after release to different environments, and the laboratory animals exposed to two different temperatures will be shown in the Symposium in September.

Description: 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.