INTRA- AND INTERSPECIFIC DIFFERENCES IN RATE OF OXYGEN CONSUMPTION IN GOBIID FISHES OF THE GENUS GILLICHTHYS

¹ Department of Zoology. University of California, Los Angeles, California

1. Rate of oxygen uptake was determined for moist fish in a Warburg apparatus. Fish acclimated to 10° were tested at 10° and 17°; those acclimated to 24° were tested at 24° and 31°. Five populations of G. mirabilis were investigated (San Francisco Bay in central California, Los Peñasquitos in southern California, San Felipe in the northern Gulf of California, Puerto San Carlos in the central Gulf, and the Salton Sea). One population of G. seta (from the upper Gulf) was studied at 24°.

2. Rate of oxygen consumption per unit weight was plotted against body weight. The regression coefficient, b, differed between populations for G. mirabilis though not in an interpretable fashion. The value of b was low at 10° and 17° (-0.14 and -0.35), and high at 24° and 31° (-0.45 and -0.63). The slopes were much lower for G. seta at 24° and 31° (-0.29 and -0.26) than for G. mirabilis.

3. The mean rates of oxygen uptake were different for the populations of G. mirabilis at all temperatures except 24°. The average rate for G. seta at 24° was lower than that for G. mirabilis, but the rates were about the same for both species at 31°.

4. The temperature coefficients, Q₁₀, varied from population to population of G. mirabilis in what seemed to be a pattern. The coefficients were lower in groups from the Gulf of California at almost all temperature intervals. Within the Pacific Coast and Salton Sea populations, the Q₁₀'s for the northern population were highest at the low acclimation temperature, and lowest at the high acclimation temperature. For all groups, the Q₁₀'s were highest when cold-acclimated (2.2 to 2.8), and lowest when warm-acclimated (1.4 to 1.6). The coefficient for warm-acclimated G. seta was high (2.0).

5. There was no apparent difference in temperature coefficients between large and small G. mirabilis for acute temperature changes. The smaller fish manifested appreciably higher Q₁₀'s than did the larger fish, however, when rates were compared after acclimation.

6. The degree of intra- and interspecific differences in the nature of the oxygen consumption was roughly of the same order of magnitude as the morphological differences reported in another article.