Efeitos da aclimatação à hipóxia crônica e intermitente na tolerância do ciclídeo-anão Apistogramma agassizii

Abstract

Amazonian fish have numerous strategies linked to capture of oxygen in response to periods of scarcity in the aquatic environment, leading them to the development of various adaptive mechanisms, whether they are physiological, morphological, biochemical or genetic. Amazon fish find absence of oxygen in their habitats during the seasonal and/or daily period and as responses to these variations, the physiological effects of chronic hypoxia and intermittent are still poorly understood. This study sought to assess the responses metabolic effects of Apistogramma agassizii dwarf cichlid affected by exposure to chronic and intermittent hypoxia. Groups of adult cichlid were exposed to hypoxia (below 1 mgO2.L -1 ) or normoxia (6.48 ± 0.04 mgO2.L -1 ) for periods that range from 96 hours for chronic hypoxia and 1 to 4 weeks for hypoxia intermittent. Subsequently the time of loss of balance in hypoxia, consumption of oxygen and activity of lactate dehydrogenase and citrate synthase enzymes were measured after the hypoxia acclimation time of each experimental group. At Cichlid exposures to low oxygen concentrations showed an increase gradual in the time of loss of balance of the species, adults acclimated for 4 weeks to intermittent hypoxia had greater reductions in metabolic rate than 46% (P=<0.0017, F=38.80) and the highest LOE that reached 90 minutes (P=<0.04, F= 12.265). The reduction in the activity of the citrate synthase enzyme, accompanied by the increased activity of the lactate dehydrogenase enzyme demonstrates that the dwarf cichlid does not increase its anaerobic potential as the species is exposed to hypoxia chronic and intermittent. When undergoing intermittent hypoxia for 4 weeks species has been shown to activate the anaerobic metabolism more efficiently, where managed to regulate oxygen consumption and metabolic pathways, while being submitted to chronic hypoxia, the cichlid activates only the metabolic pathways. This one study shows that the dwarf cichlid Apistogramma agassizii has a large phenotypic plasticity to deal with changes in dissolved oxygen. Keywords: Hypoxia; Apistogramma agassizii; anaerobic metabolism and aerobic.