Salinity tolerance and osmoregulation in the salamanderBatrachoseps

Summary

Measurements of survival in various dilutions of sea water indicate that some populations of the small (<1.5 g), terrestrial, plethodontid salamanderBatrachoseps may be among the most euryhaline of amphibians. Both intra- and inter-specific variations are evident in salinity tolerance: populations living close to sea water are more resistant than inland populations; and allB. relictus studied are more resistant thanB. attenuatus, independent of habitat. Salinity tolerance also varies directly with size, and prior acclimation to intermediate salinities improves tolerance to high salinities.

Physiological measurements reveal thatBatrachoseps elevates total osmotic pressure like other amphibians. The salamander drinks when in hypersaline media but experiences large losses of tissue water. Its mechanisms of adjusting to hypersaline conditions are distinct from the euryhaline anurans studied (Bufo viridis andRana cancrivora). The salamander shows only moderate hypernatremia and increased chloride levels. There is little or no increase in urea and free amino acids. A major portion of the increased osmotic pressure of the body fluids cannot be accounted for by either loss of water or increased NaCl and urea.