O tamanho de crenuchus spilurus influencia na tolerância e ajustes metabólicos após exposição à hipóxia?

Abstract

One of the main parameters that affects the distribution of aquatic organisms is the Dissolved oxygen. In the aquatic systems of the Amazon, fish find regularly hypoxic environments, thus having developed a series of adaptations to survive in these environments. Crenuchus spilurus is a species that occurs in environments with a wide range of oxygen variation, being found more frequently in hypoxic places as a juvenile. Thus, the objective of this study was to evaluate the tolerance and metabolic adjustments to hypoxia in C. spilurus of different sizes; adults and youth. For this, we evaluate the tolerance of the animal, which was determined by measuring the oxygen concentration in which loss of balance occurs (LOE, from English Loss of Equilibrium), and also investigated metabolic adjustments, such as metabolic rate (MO2) and activity enzymes of the energy and antioxidant metabolism of animals. Our results of LOE show that C. spilurus is a hypoxia-tolerant species and that exposure prior to hypoxia in both sizes increases their tolerance to low concentrations of oxygen. The results presented here show a metabolic regulation of animals after exposure to hypoxia, as observed by the decrease in the rate metabolic. However, this regulation does not seem to be related to the enzymes of the energy metabolism and neither to the antioxidant system, since these parameters were little affected by hypoxia, probably in response to an adjustment adaptive after seven days of exposure. We suggest, from the tolerance data, that metabolic regulation after exposure to hypoxia in C. spilurus must be associated with greater efficiency in oxygen uptake and delivery to cells, reflecting in a more effective capacity in the uptake of oxygen by the gills, as well as in the transport of this gas via the circulatory system.