Sodium and potassium in spontaneously produced salt gland secretion and tears of ducks, Anas platyrhynchos, acclimated to fresh and saline waters
The spontaneously produced salt gland secretion (SGS) and tears of the domestic duck, Anas platyrhynchos, were analyzed for sodium (Na), potassium (K), and chloride (Cl) (Cl in SGS only). Acclimation to seawater did not enhance the concentrating ability of the salt glands. The NaCl concentration exceeded that of seawater by only a small margin. The tears of saline-acclimated birds contained less Na and more K than birds drinking water with low NaCl content. Salt stress significantly increased the weight of the salt glands and of the Harderian glands; the lacrymal glands were not affected. An estimation of the relative possible contribution of the cloacal fluid, SGS, and tears to cation excretion was made.