School of Biological Sciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.
Sci Rep. 2018 Feb 27;8(1):3739. doi: 10.1038/s41598-018-22002-8.
Sloughing maintains the skins integrity and critical functionality in amphibians. Given the behavioural, morphological and osmoregulatory changes that accompany sloughing, this process is likely to be physiologically costly. Chytridiomycosis, a cutaneous disease of amphibians caused by the fungus Batrachochytrium dendrobatidis (Bd), disrupts skin function and increases sloughing rates. Moreover, mortality rates from chytridiomycosis are significantly higher in juveniles and so we hypothesised that smaller individuals maybe more susceptible to chytridiomycosis because of allometric scaling effects on the energetic and osmoregulatory costs of sloughing. We measured in-vivo cutaneous ion loss rates and whole animal metabolic rate (MR) of Green tree frogs, Litoria caerulea, over a range of body sizes both infected and uninfected frogs during sloughing. Infected animals had a greater rate of ion loss and mass-specific MR during non-sloughing periods but there were no additional effects of sloughing on either of these parameters. There were also significant interactions with body size and Bd load indicating that smaller animals with higher Bd loads have greater rates of ion loss and higher energetic demands. Our results shed light on why smaller Bd-infected anurans often exhibit greater physiological disruption than larger individuals.
蜕皮维持着两栖动物皮肤的完整性和关键功能。鉴于蜕皮伴随的行为、形态和渗透调节变化，这个过程可能在生理上是有代价的。蛙壶菌病，一种由真菌蛙壶菌（Batrachochytrium dendrobatidis，Bd）引起的两栖动物皮肤疾病，破坏了皮肤功能并增加了蜕皮率。此外，由于在能量和渗透调节方面的体型比例效应，幼体的死亡率因蛙壶菌病而显著增加，因此我们假设较小的个体可能更容易受到蛙壶菌病的影响。我们测量了感染和未感染蛙壶菌的绿树蛙（Litoria caerulea）在一系列体型范围内的活体皮肤离子损失率和整个动物代谢率（MR），包括蜕皮期和非蜕皮期。感染的动物在非蜕皮期间的离子损失率和比代谢率更高，但蜕皮对这两个参数都没有额外的影响。这些参数还与体型和 Bd 负荷有显著的相互作用，表明 Bd 负荷较高的小型动物具有更高的离子损失率和更高的能量需求。我们的研究结果阐明了为什么较小的 Bd 感染的无尾目动物通常比大型个体表现出更大的生理破坏的原因。
