Relationships between glucocorticoids and infection with Batrachochytrium dendrobatidis in three amphibian species
Relationships between glucocorticoids and infection with Batrachochytrium dendrobatidis in three amphibian species
复制标题
DOI：
10.1016/j.ygcen.2019.113269
复制
发表时间：
2020-01-01
影响因子：
2.7
通讯作者：
Richards-Zawacki, Corinne L.
中科院分区：
文献类型：
--
作者：
Hammond, Talisin T.;Blackwood, Paradyse E.;Richards-Zawacki, Corinne L.
人们经常假设，暴露于环境变化的生物体可能会经历生理压力，这可能会降低个体素质，使它们更容易患病。两栖动物是最受威胁的类群之一，特别是在疾病的背景下，但相对较少的研究探索两栖动物物种的压力和疾病之间的联系。在这里，我们以真菌病原体水蛭壶菌（Bd）和两栖动物为例，探索疾病与糖皮质激素（GCs）之间的关系，糖皮质激素是应激反应的重要组成部分。虽然以前的工作是有限的，但它已经在很大程度上确定了GCs和bd感染之间的积极关系。然而，因果关系尚不清楚，很少有研究将GC的基线（与标准生理功能相关的GC释放）和应激诱导（对急性应激源的GC释放）测量结合起来。在这里，我们在野外和圈养环境中检查了暴露于压力源之前和之后的唾液皮质酮。我们报告了三种两栖动物感染和未感染的结果，它们对这种病原体有不同的敏感性（猫蛙、蛤蛙和林蛙）。我们假设，在应激之前，受布氏病感染的动物，特别是在布氏病易感物种中，基线GCs会更高。我们还预计，在暴露于应激源后，应激诱导的GCs在bd感染动物中会降低。这些物种在基线和应激诱导的皮质酮水平上表现出显著的种间差异，尽管性别、体型和年份等其他变量通常不能预测皮质酮水平。与之前的大多数研究相反，我们发现两个物种（红毛瓢虫和黑毛瓢虫）的Bd和皮质酮之间没有关系，在最不耐Bd的物种（森林瓢虫）中，Bd感染和皮质酮之间的关系表现出环境依赖性差异：Bd阳性的森林瓢虫的基线和应激诱导的皮质酮水平明显较低，这种模式在野外比在圈养环境中更强。这些结果令人惊讶，因为过去在其他物种的研究中更经常发现bd阳性动物的GCs升高，这一模式与长期高GCs，个体质量下降和免疫抑制之间的关系相一致。这项工作强调了在两栖动物数量下降的背景下，GCs与疾病易感性的潜在相关性，同时强调了在不同背景下描述这些关系的重要性。
It is often hypothesized that organisms exposed to environmental change may experience physiological stress, which could reduce individual quality and make them more susceptible to disease. Amphibians are amongst the most threatened taxa, particularly in the context of disease, but relatively few studies explore links between stress and disease in amphibian species. Here, we use the fungal pathogen Batrachochytrium dendrobatidis (Bd) and amphibians as an example to explore relationships between disease and glucocorticoids (GCs), metabolic hormones that comprise one important component of the stress response. While previous work is limited, it has largely identified positive relationships between GCs and Bd-infection. However, the causality remains unclear and few studies have integrated both baseline (GC release that is related to standard, physiological functioning) and stress-induced (GC release in response to an acute stressor) measures of GCs. Here, we examine salivary corticosterone before and after exposure to a stressor, in both field and captive settings. We present results for Bd-infected and uninfected individuals of three amphibian species with differential susceptibilities to this pathogen (Rana catesbeiana, R. clamitans, and R. sylvatica). We hypothesized that prior to stress, baseline GCs would be higher in Bd-infected animals, particularly in more Bd-susceptible species. We also expected that after exposure to a stressor, stress-induced GCs would be lower in Bd-infected animals. These species exhibited significant interspecific differences in baseline and stress induced corticosterone, though other variables like sex, body size, and day of year were usually not predictive of corticosterone. In contrast to most previous work, we found no relationships between Bd and corticosterone for two species (R. catesbeiana and R. clamitans), and in the least Bd-tolerant species (R. sylvatica) animals exhibited context-dependent differences in relationships between Bd infection and corticosterone: Bd-positive R. sylvatica had significantly lower baseline and stress-induced corticosterone, with this pattern being stronger in the field than in captivity. These results were surprising, as past work in other species has more often found elevated GCs in Bd-positive animals, a pattern that aligns with well-documented relationships between chronically high GCs, reduced individual quality, and immunosuppression. This work highlights the potential relevance of GCs to disease susceptibility in the context of amphibian declines, while underscoring the importance of characterizing these relationships in diverse contexts.