Influence of seasonality on the natural modulation of oxidative stress biomarkers in mangrove crab Ucides cordatus (Brachyura, Ucididae).

The estuaries are characterized by the formation of salinity gradients and are frequently associated with anthropic activities. Studies that show the condition of organisms against the natural environmental variations are fundamental for future evaluation of environmental change due to anthropic impacts. Biomarkers are useful tools defined as biological changes in low levels of organization induced by stressors and considered as predictive responses of more severe effects. The aim of this study was to characterize the modulation of biochemical biomarkers in Ucides cordatus against the natural variation a pristine mangrove forest in an Amazonic estuary (Japerica Bay). The samplings were carried out throughout one year at rainy-dry transitional period (June/2013), dry period (September/ 2013), dry-rainy transitional period (November/ 2013) and rainy period (February/ 2014) in the lower, middle and upper estuary. The biochemical biomarkers evaluated were glutathione-S-transferase (GST), glutamate cysteine-ligase (GCL), total antioxidant capacity (ACAP), reduced glutathione (GSH) concentration and the lipid peroxidation (LPO). There was a decrease in the activity of both enzymes, GSH concentration and lower LPO in the rainy-dry transitional period for the organisms of all sites, pointing to this period as a season of greater metabolic stability. The organisms, especially those of the middle estuary, presented physiological plasticity against the variations of the environment which they are submitted. Seasonality, more than salinity influence due to position in estuary, is the main modulator of biomarkers. Also, our results indicate that the species presents high viability for biomonitoring studies.