STUDIES OF THE RESPIRATORY METABOLISM OF WARM AND COOL SPRING FISHES

Abstract

Fishes (Crenichthys baileyi) living in a warm spring at temperatures of 35° to 37° have a far higher rate of oxygen consumption (ml./-gm./hr.) than fishes of the same species living in a cool spring (21°). The ratio, when fishes of approximately the same weight are compared, is not far from 2 to 1. Cool spring fishes, when transferred to the warm spring, die so rapidly that measurements of oxygen consumption are not practicable. When the converse experiment is performed (transfer of warmspring fishes to the cool spring), they live in health for some days, and may perhaps do so indefinitely. Changes in their rate of oxygen consumption are as follows: (1) A rapid fall occurs within the first few hours. (2) At the close of a day, the metabolic rate (oxygen consumption) is about the same as that of fishes native to the cool spring. If any difference exists, when specimens of the same size are compared, this is probably slight. This failure of the metabolic rate of warm-spring fishes to fall below that of cool-spring fishes, when transferred to the latter medium, accords with previous experiments at these same springs in which the cyanide method was used, but it does not accord with experiments performed upon some other species in the laboratory. A marked inverse correlation exists between size (age) and metabolic rate. This correlation is more marked at high temperatures than at lower ones. Thus the curves for the four size-groups of warm-spring fishes here considered converge strongly during the test in cool water, coming together at nearly a common point by the end of the day. This last fact harmonizes with the fact that the correlation between size and metabolic rate, while observable, was found to be low among the cool spring fishes. The oxygen consumption of smaller fishes is much more affected by temperature changes than is that of the larger specimens. In other words, the temperature coefficient is higher for the smaller (younger) animals, a fact which does not appear to agree with most results which have been reported for other organisms.