The effect of temperature on the oxygen equilibria of fish hemoglobins in relation to environmental thermal variability

Abstract 1. We have measured the temperature dependence of the oxygen equilibria of blood and hemoglobin solutions from four neotropical and three temperate zone fishes. 2. Significant differences exist in the heats of oxygenation of the bloods but not the hemoglobin solutions from different species. 3. The differences in thermal sensitivity of the oxygenation of the bloods appear to depend on differences in intracellular pH, organic phosphates and other ligand-linked variables and not the intrinsic enthalpies of the oxygenation of the hemoglobins themselves.