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 (<italic>Lithobates catesbeiana</italic>), semi-terrestrial Pacific chorus frog (<italic>Pseudacris sierra</italic>), and terrestrial western toad (<italic>Anaxyrus boreas</italic>) were tested in the laboratory for patterns and preferences in the maintenance of body hydration levels. <italic>L. catesbeiana</italic> and <italic>P. sierra</italic> 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. <italic>A. boreas</italic> 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.