Dehydration Hardly Slows Hopping Toads (Rhinella granulosa) from Xeric and Mesic Environments

Abstract

The locomotor capacity of amphibians depends strongly on temperature and hydration. Understanding the potential interactions between these variables remains an important challenge because temperature and water availability covary strongly in natural environments. We explored the effects of temperature and hydration on the hopping speeds of Rhinella granulosa, a small toad from the semiarid Caatinga and the Atlantic Rain Forest in Brazil. We asked whether thermal and hydric states interact to determine performance and whether toads from the Caatinga differ from their conspecifics from the Atlantic Forest. Both dehydration and cooling impaired hopping speed, but effects were independent of one another. In comparison to performances of other anurans, the performance of R. granulosa was far less sensitive to dehydration. Consequently, dehydrated members of this species may be able to sustain performance through high body temperatures, which agrees with the exceptional heat tolerance of this species. Surprisingly, toads from both the Caatinga and the Atlantic Forest were relatively insensitive to dehydration. This observation suggests that migration or gene flow between toads from the forest and those from a drier region occurred or that toads from a dry region colonized the forest secondarily.

Trading heat and hops for water: Dehydration effects on locomotor performance, thermal limits, and thermoregulatory behavior of a terrestrial toad

“…2013; Titon and Gomes, 2010). Our results clearly showed that the better hydrated the animal, the better was their absolute locomotor performance in all temperatures tested.…”

“…2013 and references therein). Moreover, previous studies found that locomotion may be greatly influenced by temperature (Rome, Stevens, & John‐Alder 1992) and dehydration (Preest & Pough 1989) in amphibians.…”

Local adaptation in mainland anole lizards: Integrating population history and genome–environment associations

“…Because physiological tolerances to abiotic conditions constrain organismal fitness (Navas, ), it has been suggested that the occurrence of any given species across various environments may be associated with local adaptation (Bridle & Vines, ; Hohenlohe et al, ; Huey, Gilchrist, Carlson, Berrigan, & Serra, ). Yet, experimental studies indicate that physiological function can be highly conserved within species over wide environmental gradients (e.g., Crowley, ; Hertz, Huey, & Nevo, ; John‐Alder, Barnhart, & Bennett, ; Prates & Navas, , Prates, Angilleta, Wilson, Niehaus, & Navas, ; Van Damme, Bauwens, Castilla, & Verheyen, ), and this lack of phenotypic differentiation has been associated with the homogenizing effects of population gene flow (Bridle & Vines, ; Lenormand, ). It is therefore unclear to which extent the occurrence of species in distinct environments is linked to local adaptation and associated genetic differentiation.…”

Effects of variations of osmolarity on behavior in Leptodactylus macrosternum Miranda-Ribeiro, 1926 (Leptodactylidae, Anura, Amphibia)

“…From this, we can infer that greater osmotic concentrations in surrounding water are physiologically stressful for this species. It is known that dehydration stress (in this study, caused by air or saline media) is an important factor for the increase of frequency or duration of postures associated with water conservation in anurans (Heatwole et al, 1969;Brekke et al, 1991;Hillyard et al, 2007;Pough et al, 1983;Hillyard et al, 1998;Prates et al, 2013;Taylor et al, 1999;Viborg and Rosenkilde, 2001;Tran et al, 1992) Hillyard et al (1998, while studying the physiological processes involved in the behavioral response of Bufo marinus, normally hydrated as well as dehydrated (loss of 10% of initial body mass), and rehydration in NaCl solutions with concentrations of 250 mmol/L and 500 mmol/L, saw that both groups exhibited the "ventral skin down" posture (equivalent to this study's "a" or water conservation posture), but the normally hydrated individuals kept themselves in this posture for a shorter time than individuals which were dehydrated.…”