The effect of environmental pH on sodium balance in the red-spotted newt, Notophthalmus viridescens.

Sodium influx and efflux of the red-spotted newt, Notophthalmus viridescens, at two pHs were investigated in efts and adults in water and on land. The sodium efflux rate constant was not affected by pH. Efflux was generally greater under aquatic than terrestrial conditions, and for efts than for adults. In an aquatic setting, both adults and efts were able to maintain sodium balance at pH 5, but exhibited net sodium loss at pH 3. Sodium influx was greater in efts at pH 5 than in any other group. Adults in all treatments lost mass during the experiment, while efts in all treatments were able to maintain body mass. In their normal terrestrial environment, red efts probably avoid substantial sodium fluxes by maintaining a hydrophobic skin, which decreases contact with soil solutions.