The problem of respiratory acclimatization

Abstract

1. In 1916 August Krogh called attention to the fact that related species, or animals belonging to the same species, sometimes inhabit localities with extremely different temperatures. In such cases it would appear unlikely from a teleological point of view that the respiratory exchange should differ as much as the temperature difference would ordinarily imply. According to K rogh one would expect that animals living at a very low temperature should show a relatively high metabolism compared with others living normally at a high temperature. 2. The hypothesis advanced by Krogh with special reference to great temperature differences has been treated in this paper with reference to a fairly small and seasonal temperature difference: The temperature difference in summer between a lake, Rorbaek So, having a temperature of 18°, and a brook, Funder Aa, with a temperature of 11° C. In both localities there was a large population of Ancylus fluviatilis and this species was used as the experimental animal. 3. The comparative experiments were carried out at 11° C and 18° C for both the cold-water form of Ancylus fluviatilis from the brook and the warm-water form from the lake. 4. The experiments have shown no such acclimatization with regard to the oxygen consumption of the two Ancylus fluviatilus populations that live in different temperature environments, as was expected according to the above-mentioned hypothesis. But there exists an acclimatization of the opposite nature (a “reversed acclimatization”): The animals from the summer-warm environment (18° C) had acquired a greater oxygen consumption than those from the summer-cold environment (11° C). 5. Aug. Krogh (1914, p. 504) established a curve showing the quantitative relation between the temperature and the standard metabolism in animals. The increase in the oxygen consumption of Ancylus fluviatilis with increasing temperature — as found in the experiments at 11° and at 18° C — agrees well with Krogh's curve. 6. The oxygen consumption increases 1.9 times when the temperature of the experimental animals increases from 11° C to 18° C. The “reversed acclimatization” found for Ancylus fluviatilis is about 1.4. It means that the observed respiration of the warmwater animals in relation to that of the cold-water animals is about 1.4 times greater than would be implied from the temperature difference between their habitats. 7. The oxygen determinations made in this study were carried out by means of the polarometric method.