Larval environment alters amphibian immune defenses differentially across life stages and populations

Recent global declines, extirpations and extinctions of wildlife caused by newly emergent diseases highlight the need to improve our knowledge of common environmental factors that affect the strength of immune defense traits. To achieve this goal, we examined the influence of acidification and shading of the larval environment on amphibian skin-associated innate immune defense traits, pre and post-metamorphosis, across two populations of American Bullfrogs (Rana catesbeiana), a species known for its wide-ranging environmental tolerance and introduced global distribution. We assessed treatment effects on 1) skin-associated microbial communities and 2) post-metamorphic antimicrobial peptide (AMP) production and 3) AMP bioactivity against the fungal pathogen Batrachochytrium dendrobatidis (Bd). While habitat acidification did not affect survival, time to metamorphosis or juvenile mass, we found that a change in average pH from 7 to 6 caused a significant shift in the larval skin microbial ...近年来，新兴传染病引发的全球野生动物种群衰退、局部灭绝与物种绝灭现象，凸显了我们亟需加深对影响免疫防御性状强度的常见环境因子的认知。为达成这一研究目标，我们以两种群的美洲牛蛙（American Bullfrogs, Rana catesbeiana）——一种以宽泛环境耐受能力与全球入侵分布著称的物种——为研究对象，探究了幼体环境酸化与遮光对两栖动物变态前、变态后皮肤相关先天免疫防御性状的影响。我们针对三项指标评估了处理效应：1）皮肤相关微生物群落；2）变态后个体的抗菌肽（antimicrobial peptide, AMP）产生量；3）抗菌肽对真菌病原体蛙壶菌（Batrachochytrium dendrobatidis, Bd）的生物活性。尽管栖息地酸化对幼体存活率、变态时长及幼体体重均无显著影响，但我们发现水体平均pH值从7降至6时，幼体皮肤微生物群落发生了显著改变……