STUDIES ON THE PHYSIOLOGICAL VARIATION BETWEEN TROPICAL AND TEMPERATE ZONE FIDDLER CRABS OF THE GENUS UCA. II. OXYGEN CONSUMPTION OF WHOLE ORGANISMS

¹ Duke University Marine Laboratory, Beaufort, North Carolina and the Department of Zoology, Duke University, Durham, North Carolina

1. The rate of oxygen consumption of seven species of Uca from the tropical and temperate zones was determined over a graded temperature series. All species had a similar recent thermal history.

2. Starvation resulted in an initial decrease in metabolic rate followed by a relatively constant rate in Uca pugnax.

3. Generally increased temperature resulted in increased rates of oxygen consumption. However, in some cases a given temperature range had little or no effect on metabolism, while at other temperatures a marked increase resulted.

4. Q₁₀'s of temperate and tropical zone species were similar at intermediate and higher temperatures but differed at lower thermal levels. Q₁₀ varied with size and temperature levels. Lower Q₁₀'s were obtained at higer temperatures.

5. Intra- and interspecific comparisons of metabolism-size relationships were made on data obtained at various temperatures. The slopes of the regression varied with temperature and species.

6. When comparing the metabolic response of two latitudinally isolated populations of Uca rapax with a closely related temperate zone species, the pattern of the northernmost population of U. rapax was intermediate between the tropical and temperate zone forms.

7. Although no seasonal variation in metabolism was observed in tropical species, fluctuation was observed in a temperate zone species.