Meeting Abstract
Amphibians are ectotherms with water-permeable skin, and so they must thermoregulate and hydroregulate to cope with a variable environment. Amphibians must maintain body temperatures and hydration levels that allow for adequate organismal performance of daily activities. Recent work suggests that temperature and moisture effects can interact, thus moisture availability may affect thermoregulation and body temperature may affect hydroregulation. For our study, we examined thermal and moisture preferences in two species of ranid frogs (Lithobates clamitans and L. sylvaticus), and one species of bufonid toad (Anaxyrus americanus). These species provide informative comparisons, as the two ranids are closely related, but L. sylavaticus and A. americanus are predominantly terrestrial, frequenting drier habitats than the hydrophilic L. clamitans. To determine thermal and moisture preferences of the frogs, we used thermal and moisture gradients. The thermal gradient was kept either dry or moist with temperatures ranging from 5 to 35°C. The moisture gradient had peat moss ranging from dry to extremely wet, and was kept at 10°C, 20°C, or 30°C. In both gradients, frogs were either dehydrated to 80% standard mass or fully hydrated. In the thermal gradient, dehydrated frogs of all three species preferred lower body temperatures than hydrated frogs, suggesting that frogs select body temperatures that minimize water loss. In the moisture gradient, L. clamitans preferred wetter conditions when dehydrated, as expected, but the two terrestrial species either did not differ in their moisture preferences or preferred wetter conditions when hydrated. This may suggest that hydroregulation is more important in aquatic species that may have lower capacity to cope with dehydration.
