Salinity Adaptation in the Salamander Batrachoseps

Abstract

(1) Batrachoseps attenuatus and B. major were successfully acclimated to 600 m-osmol NaCl and 400 m-osmol sucrose solutions. (2) Accumulation of sodium and an increased rate of synthesis of urea provide substantial increases in plasma concentrations of these solutes. Sodium concentrations in excess of 230 mM and urea concentrations in excess of 200 mM indicate that these are the two major solutes (plus anions) responsible for elevation of osmotic concentration in Batrachoseps. (3) Batrachoseps exhibits a water balance response upon dehydration (greater than twofold increase in cutaneous uptake, 50% reduction in urine production). Urine production, estimated from bladder contents, was significantly reduced in salamanders acclimated to sucrose solutions compared to animals acclimated to tap water or saline of equivalent osmotic concentration. (4) Plasma urea concentration was equivalent to urine urea concentration when Batrachoseps was kept in tap water and during short term saline acclimation. After long term saline acclimation, urine urea concentration was one-fourth the plasma urea concentration.