1. In the freshwater adapted rainbow trout, urine flow markedly increased during periods of exercise in a swimming respirometer. 2. Over a range of oxygen consumptions from "standard" to nearly "active metabolic rates", oxygen and water fluxes exhibited a highly significant positive correlation in individual fish. The results were indicative of covariation of the oxygen and water permeabilities of the gills. 3. A triphasic fluctuation in body weight, considered a measure of water balance, occurred during the course of exercise. On the basis of weight change and urine flow data, a tentative model of water regulation during swimming is presented. 4. Urinary levels of sodium and potassium tended to fall at high urine flows and rise at lowflows. Calcium and magnesium concentrations underwent simultaneous fluctuations which did not always correspond to alterations in urine volume. 5. The renal excretion rates of all four cations increased significantly during swimming activity.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology
- Behavioral Neuroscience