Slack K L, Groffen J, Davis A K, Hopkins W A
Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA 24061, USA.
Odum School of Ecology, University of Georgia, Athens, GA 30602, USA.
Integr Org Biol. 2025 Apr 3;7(1):obaf006. doi: 10.1093/iob/obaf006. eCollection 2025.
The emergence and spread of infectious diseases is a significant contributor to global amphibian declines, requiring increased surveillance and research. We assessed host-vector-parasite dynamics using a population of eastern hellbender salamanders () that harbor leeches () that transmit endoparasitic blood parasites ( spp) to the host, with coinfection frequently occurring. We centered our study on adult males throughout their extended 8-month paternal care period because recent research indicates that nest failure caused by lack of paternal care and filial cannibalism is contributing to hellbender population declines. Recognizing the potential for parasites to modulate host physiology and behavior, we explored how infection severity influences paternal health and reproductive success. We assessed white blood cell profiles of adult male hellbenders in response to parasites, coinfection, and seasonal temperature fluctuations, while also investigating whether parasite infection or coinfection was predictive of nest success. We found that hellbenders exhibited seasonal shifts in white blood cell indices; as temperatures increased across seasons (from 5°C to 20°C), the proportion of neutrophils and eosinophils decreased (by 14% and 46%, respectively) in circulation while the proportion of lymphocytes and basophils increased (by 8% and 101%, respectively). Moreover, the proportion of neutrophil precursors increased by 80% under colder temperatures, which signifies seasonal immune cell recruitment. We demonstrated that neutrophils and eosinophils increased while lymphocytes decreased in response to leech infection. However, as leech and trypanosome infection intensity increased together, the proportion of lymphocytes increased while neutrophils and eosinophils decreased, underscoring the complex interactions between coinfection and immune responses of hellbenders that warrant future research. Despite the influence of infection and coinfection on hellbender physiology, we detected no evidence to support the hypothesis that parasites influence the likelihood of nest failure or whole-clutch filial cannibalism. In light of amphibian declines being exacerbated by climate change and disease, our study emphasizes the need to establish hematological reference values that account for physiological adaptations to seasonal fluctuations in temperature and different life history stages and to study the physiological responses of imperiled amphibian species to parasites.
传染病的出现和传播是导致全球两栖动物数量减少的一个重要因素，这需要加强监测和研究。我们利用东部隐鳃鲵种群评估宿主-媒介-寄生虫动态，这些隐鳃鲵携带水蛭，而水蛭会将内寄生血液寄生虫传播给宿主，且经常发生共感染。我们的研究集中在成年雄性隐鳃鲵长达8个月的育幼期，因为最近的研究表明，缺乏父性照料和同类相食导致的巢穴失败是隐鳃鲵种群数量下降的原因之一。认识到寄生虫可能调节宿主生理和行为，我们探讨了感染严重程度如何影响父性健康和繁殖成功率。我们评估了成年雄性隐鳃鲵对寄生虫、共感染和季节性温度波动的白细胞谱，同时还研究了寄生虫感染或共感染是否能预测巢穴成功。我们发现，隐鳃鲵的白细胞指数呈现季节性变化；随着季节温度升高（从5°C到20°C），循环中嗜中性粒细胞和嗜酸性粒细胞的比例下降（分别下降14%和46%），而淋巴细胞和嗜碱性粒细胞的比例增加（分别增加8%和101%）。此外，在较冷温度下，嗜中性粒细胞前体的比例增加了80%，这表明存在季节性免疫细胞募集。我们证明，感染水蛭后嗜中性粒细胞和嗜酸性粒细胞增加，而淋巴细胞减少。然而，随着水蛭和锥虫感染强度共同增加，淋巴细胞比例增加，而嗜中性粒细胞和嗜酸性粒细胞减少，这凸显了隐鳃鲵共感染与免疫反应之间复杂的相互作用，值得未来研究。尽管感染和共感染会影响隐鳃鲵的生理，但我们没有发现证据支持寄生虫会影响巢穴失败或整窝同类相食可能性的假设。鉴于气候变化和疾病加剧了两栖动物数量的减少，我们的研究强调需要建立血液学参考值，以考虑到对温度季节性波动和不同生活史阶段的生理适应，并研究濒危两栖动物物种对寄生虫的生理反应。
