Blood ionic and acid–base status in rainbow trout (Salmo gairdneri) following rapid transfer from freshwater to seawater: effect of pseudobranch denervation

Effect of pseudobranch denervation on the ability of Salmo gairdneri to regulate blood ionic and acid–base balance was investigated in freshwater and following transfer to seawater. Denervation of the pseudobranch did not affect internal ionic or acid–base equilibrium in freshwater. Plasma [Cl−], [Na+], pH, total [Formula: see text], and partial pressure of [Formula: see text] of trout were affected by transfer from freshwater to seawater, and by transfer back to freshwater. These ionic and acid–base responses were not affected by denervation of the pseudobranch. It is concluded that alone, the pseudobranch plays little or no role in ionic and osmotic regulation during transfer between freshwater and seawater.