COMPARATIVE ANALYSIS OF EVAPORATIVE WATER LOSS OF ANURANS OF DIFFERING ECOMORPHOLOGIES

Author

Andrew John Capitosti, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2025

Degree Name

Master of Science

Department

Zoology

First Advisor

Boyles, Justin

Abstract

Water serves as a mediator in nearly every biological process from the cellular level to the whole organism. In most vertebrates, water accounts for up to 70% of organismal body mass making osmoregulation an essential aspect of homeostasis. Notably, many vertebrates often use osmoregulation, in the form of total evaporative water loss (TEWL), to thermoregulate, and vice versa. With climate change making habitats warmer and more arid, it is increasingly important to understand how these homeostatic mechanisms are connected. Amphibians serve as a model for examining these aspects of homeostasis. Notably, amphibians have a unique life history where larval stages are often tied closely to water. This has led amphibians to evolve mechanisms, often tied to their ecological habits, to aid in water conservation. Further, amphibians allow for an examination of how environmental and ecological factors affect organismal TEWL. I first examined if hand-held evaporimeters measuring cutaneous evaporative water loss (CEWL) could be used to document general water loss trends in amphibians. I then examined how temperature affects the TEWL of five anuran species of differing ecologies, the Gray Tree Frog (Dryophytes versicolor), Green Tree Frog (Hyla cinerea), Southern Leopard Frog (Lithobates sphenocephalus), Green Frog (Rana clamitans), and Fowler’s Toad (Anaxyrus fowleri). Hand-held evaporimeters hold promise for future studies examining water loss. Specifically, I found that while CEWL might not directly reflect TEWL, hand-held evaporimeters reliably describes general osmoregulation trends. Further, a species ecology, along with environmental temperature and humidity all greatly influence TEWL. The two arboreal species, the Gray Tree Frog and Green Tree Frog, displayed significantly lower TEWL rates at all temperatures when compared to the other species. I also found that all species displayed an ability to conserve water as temperature increased, likely due to increased humidity. Overall, I found that hand-held evaporimeters are useful in documenting water loss trends and could provide a repeatable method to acquire large scale water loss data in the field. Additionally, I found that TEWL is influenced by many environmental factors and a species ecology. Further, I emphasize the importance to examine these factors together allowing for a better understanding of amphibian osmoregulation.