Patterns of Hydroregulation in Representatives from Three Anuran Families: Anaxyrus, Lithobates and Pseudacris

Abstract

Amphibian homeostatic processes such as thermoregulation and hydroregulation and their effects on physiological parameters have been extensively studied, but the inherent control of hydroregulation as a function of itself remains relatively unknown. This thesis addresses patterns and preferences in hydration levels of three species of anurans with different lifestyles and habits. The aquatic American Bullfrog (Lithobates catesbeiana), semi-terrestrial Pacific chorus frog (Pseudacris sierra), and terrestrial western toad (Anaxyrus boreas) were tested in the laboratory for patterns and preferences in the maintenance of body hydration levels. L. catesbeiana and P. sierra preferred high hydration levels ranging from 85%-99% and 83%-99% respectively, which are consistent with their propensity to remain near water, even during foraging. A. boreas preferred a wide range of hydrations of 62%-99%, suggesting that routine activities away from water including hibernation and active foraging allow western toads to tolerate significantly low hydration levels.