Department of Biomedical and Diagnostic Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, TN, 37996, USA.
Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, St. Petersburg, FL, 33701, USA.
Sci Rep. 2023 Feb 3;13(1):1982. doi: 10.1038/s41598-023-28334-4.
Hellbenders (Cryptobranchus alleganiensis) are large, aquatic salamanders from the eastern United States. Both subspecies, eastern and Ozark hellbenders, have experienced declines resulting in federal listing of Ozark hellbenders. The globally distributed chytrid fungus, Batrachochytrium dendrobatidis (Bd) has been detected in both subspecies, and Batrachochytrium salamandrivorans (Bsal) poses a new threat if introduced into North America. Ozark hellbenders also suffer a high prevalence of toe lesions of unknown etiology, with changes in host immunocompetence hypothesized to contribute. Antimicrobial peptides (AMPs) secreted from dermal granular glands may play a role in hellbender health. We collected skin secretions from free-ranging hellbenders and enriched them for small cationic peptides used for growth inhibition assays against Bd and Bsal. Generalized linear mixed models revealed the presence of active toe lesions as the strongest and only significant predictor of decreased Bd inhibition by skin peptides. We also found skin secretions were more inhibitory of Bsal than Bd. MALDI-TOF mass spectrometry revealed candidate peptides responsible for anti-chytrid activity. Results support the hypothesis that hellbender skin secretions are important for innate immunity against chytrid pathogens, and decreased production or release of skin peptides may be linked to other sub-lethal effects of disease associated with toe lesions.
穴蝾螈（Cryptobranchus alleganiensis）是一种来自美国东部的大型水生蝾螈。两个亚种，东部穴蝾螈和欧扎克穴蝾螈，都经历了数量下降，导致欧扎克穴蝾螈被列入联邦濒危物种名单。分布在全球范围内的蛙壶菌（Batrachochytrium dendrobatidis，Bd）已在这两个亚种中被检测到，如果这种真菌被引入北美，蛙壶菌新种（Batrachochytrium salamandrivorans，Bsal）将构成新的威胁。欧扎克穴蝾螈还患有高发性未知病因的脚趾病变，宿主免疫能力下降被认为是导致这种病变的原因之一。从真皮颗粒腺分泌的抗菌肽（Antimicrobial peptides，AMP）可能在穴蝾螈的健康中发挥作用。我们从自由生活的穴蝾螈身上采集皮肤分泌物，并对其进行浓缩，以获取用于生长抑制测定的小阳离子肽，这些测定用于对抗 Bd 和 Bsal。广义线性混合模型显示，活跃的脚趾病变是皮肤肽对 Bd 抑制作用降低的最强和唯一显著预测因子。我们还发现，皮肤分泌物对 Bsal 的抑制作用强于 Bd。MALDI-TOF 质谱揭示了负责抗壶菌活性的候选肽。研究结果支持了这样一种假设，即穴蝾螈的皮肤分泌物对抵抗壶菌病原体的先天免疫很重要，皮肤肽的产生或释放减少可能与与脚趾病变相关的其他亚致死疾病效应有关。
