Abstract
Amphibians have been declining in both diversity and abundance due in large part to habitat degradation and the prevalence of emerging diseases. Although stressors can suppress the immune system, affecting an individual's health and susceptibility to pathogens, established methods for directly collecting stress hormones are not suitable for rapid field use or for use on threatened and endangered species. To overcome these challenges, we are developing an innovative method to collect and measure amphibian glucocorticoid secretions using non-invasive dermal swabs. We tested this methodology using multiple terrestrial, semi-aquatic and fully aquatic species. We swabbed the dorsal side of each animal six times and then induced a stressor of either hand-restraint, ACTH injection, or saline as a control. We then repeated swab collection immediately after the stressor and at 15, 30, 45, 60, 90 and 120 min intervals. Cortisol enzyme immunoassay detected changes in cortisol post-stressor. We also tested this methodology in the field and were successfully able to detect glucocorticoids from multiple species at varying life stages. When using in the field, capture technique should be considered since it may impact stress levels in certain species. Upon further testing, this novel method may be used to greatly increase our understanding of amphibian health especially as disease and environmental changes continue to impact fragile populations.
Highlights
The rapid decline of amphibian populations is attributed to a complex suite of natural and anthropogenic-induced environmental challenges including, but not limited to, predation, resource availability, loss and degradation of habitat, invasive species, climate change and disease outbreaks
Because GCs can be produced in a range of other sites besides the interrenal area, including skin (Zouboulis, 2004), we considered how informative dermal swabs may be for understanding amphibian endocrinology
To examine application of this technique for field cortisol sampling, we focused collection efforts on American bullfrogs (L. catesbeianus), green frogs (L. clamitans) and northern leopard frogs
Summary
The rapid decline of amphibian populations is attributed to a complex suite of natural and anthropogenic-induced environmental challenges including, but not limited to, predation, resource availability, loss and degradation of habitat, invasive species, climate change and disease outbreaks. These abiotic and biotic factors interact in such a way that interspecific and intraspecific differences may be observed in response to similar environmental threats (Blaustein and Kiesecker, 2002; Hayes et al, 2010). It is important to understand how environmental conditions impact individuals, keying in on factors that may affect disease susceptibility
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