Extra-renal salt excretion in clapper and king rails

Abstract

1. 1. The concentration and volume of salt gland secretion (SGS) were measured in newly captured, freshwater (FW) and sea-water (SW) acclimated clapper rails (permanent salt marsh species) and king rails (wintering salt marsh species), orally loaded with 10% NaCl (10 ml/kg). 2. 2. Newly captured clapper rails produced SGS at a higher rate and concentration than newly captured king rails. Maintaining clapper rails on SW did not affect SGS rate or concentration, but raised king rail SGS to clapper rail levels. After acclimation to FW, the SGS concentration decreased by about 10%, flow rate decreased by about 35% and extra-renal Cl excretion decreased 30–40% in both species. 3. 3. Following SW acclimation, both rail species produced SGS of a concentration characteristic of more marine species, such as the gull, but the SGS flow rate was much slower, so that rail chloride excretion (mg/min) was about 10% that of a gull.