Effects of temperature, sex, and gravidity on the metabolism of Small-Mouthed Salamanders, Ambystoma texanum, during the reproductive season

Amphibians that breed in early spring may encounter considerable variation in ambient temperature. In this study I investigated how the metabolic rate of male and female Small-Mouthed Salamanders (Ambystoma texanum) is influenced by variation in temperature (5-20 degrees C) during the reproductive season. As expected, both rates of resting oxygen consumption (VO2) and resting carbon dioxide production (VCO2) increased with increasing temperature. Both measures of respiration were significantly higher in gravid females than in males and postgravid females across all temperatures. Moreover, the VO2 of gravid females increased more with increasing temperature than did those of either males or postgravid females. These findings suggest that variation in ambient temperature may have an important influence on the energetic cost of reproductive activity in males and females in this species and in other spring-breeding amphibians.