FINKLER, M.S.; Indiana Univ. Kokomo: Effects of Temperature, Sex, and Gravidity on the Metabolism of Small-Mouthed Salamanders, Ambystoma texanum.

Amphibians that breed in early spring may encounter considerable variation in ambient temperature. In this study, I investigated how differences in the metabolic rate of male and female small-mouthed salamanders during the reproductive season are influenced by variation in temperature (5-20 &degC). Both rates of oxygen consumption (VO₂) and carbon dioxide production (VCO₂) were significantly higher in gravid females than males and post-gravid females across temperatures. Moreover, the VO₂ of gravid females increased more with increasing temperature than did the VO2 of either males or post-gravid females. Respiratory quotients (RQ) of gravid females (0.9-1.0 across temperatures) were generally higher than were those of either males or post-gravid females (0.7-0.8 across temperatures), suggesting a heavier reliance on carbohydrate and/or protein catabolism to fuel metabolism in gravid females. These findings suggest that ambient temperatures may have considerable influence on the differences in energetic cost of reproduction between males and females in this species and in other spring-breeding amphibians.