Data from: Skin sloughing in susceptible and resistant amphibians regulates infection with a fungal pathogen

The fungal pathogen Batrachochytrium dendrobatidis (Bd) has been implicated in amphibian population declines globally. Given that Bd infection is limited to the skin in post-metamorphic amphibians, routine skin sloughing may regulate infection. Skin sloughing has been shown to reduce the number of cultivatable microbes on amphibian skin, and Bd infection increases skin sloughing rates at high loads. However, it is unclear whether species specific differences in skin sloughing patterns could regulate Bd population growth on the skin, and influence subsequent infection dynamics. We exposed five Australian frog species to Bd, and monitored sloughing rates and infection loads over time. Sloughing reduced Bd load on the ventral skin surface, in all five species, despite wide variation in susceptibility to disease. In the least susceptible species, an increase in sloughing rate occurred at lower infection loads, and sloughing reduced Bd load up to 100%, leading to infection clearance. Conversely, the drop in Bd load with sloughing was only temporary in the more susceptible species. These findings indicate that the ability of sloughing to act as an effective immune defence is species specific, and they have implications for understanding the pattern of Bd population growth on individual hosts, as well as population-level effects.

全球范围内，真菌病原体蛙壶菌（Batrachochytrium dendrobatidis, Bd）已被证实与两栖动物种群衰减密切相关。鉴于蛙壶菌的感染仅局限于变态后两栖动物（post-metamorphic amphibians）的皮肤，规律性的皮肤蜕皮（skin sloughing）或可调控其感染进程。已有研究表明，皮肤蜕皮可减少两栖动物皮肤表面的可培养微生物（cultivatable microbes）数量，而高负荷的蛙壶菌感染会提升宿主的蜕皮速率。但目前尚不明确，不同物种间皮肤蜕皮模式的特异性差异，是否能够调控皮肤表面蛙壶菌的种群增长，并进而影响后续的感染动态。本研究将5种澳大利亚蛙类暴露于蛙壶菌环境中，并持续监测其蜕皮速率与感染负荷（infection loads）随时间的变化。尽管各物种对疾病的易感性（susceptibility to disease）存在显著差异，但皮肤蜕皮均可降低5种蛙类腹侧皮肤表面的蛙壶菌负荷。在疾病易感性最低的物种中，当感染负荷处于较低水平时，其蜕皮速率便会升高，且蜕皮可将蛙壶菌负荷降低至100%，实现感染清除。与之相反，在易感性更高的物种中，皮肤蜕皮带来的蛙壶菌负荷下降仅为暂时性的。上述研究结果表明，皮肤蜕皮作为一种有效的免疫防御（immune defence）手段，其功能存在物种特异性；该发现对于理解蛙壶菌在宿主个体上的种群增长模式，以及种群层面的感染效应均具有重要意义。