The aim of this study was to investigate the effect on an increase of temperature on the net ion fluxes on Metynnis hypsauchen, a teleost species from the Rio Negro. Fish were collected in the Anavilhanas archipelago, Rio Negro, Amazon. After 24 h adaptation fish were placed in individual chambers served with a steady flow of recirculated water. Na+ and Cl- fluxes were determined at 26 and 33ºC. After 18 h in the chambers, fish presented an influx of Na+ and Cl-, and the temperature raise to 33ºC led to an efflux of both ions, which remained even after 6 h in this temperature. Six hours were not enough to promote a significant reduction of net ion effluxes, but certainly the fluxes would be in net balance after a longer period of time, since this species can be exposed to this temperature in its natural environment.
Metynnis hypsauchen; temperature; ion fluxes
