Gill paracellular permeability and the osmorespiratory compromise during exercise in the hypoxia-tolerant Amazonian oscar (Astronotus ocellatus)

In the traditional osmorespiratory compromise, fish increase their effective gill permeability to O2 during exercise or hypoxia, and in consequence suffer unfavorable ionic and osmotic fluxes. However oscars, which live in the frequently hypoxic ion-poor waters of the Amazon, actually decrease ionic fluxes across the gills during acute hypoxia without changing gill paracellular permeability, and exhibit rapid paving over of the …