The amphibian chytrid fungus, Batrachochytrium salamandrivorans (Bsal) threatens salamander biodiversity. The factors underlying Bsal susceptibility may include glucocorticoid hormones (GCs). The effects of GCs on immunity and disease susceptibility are well studied in mammals, but less is known in other groups, including salamanders. We used Notophthalmus viridescens (Eastern Newts) to test the hypothesis that GCs modulate salamander immunity. We first determined the dose required to elevate corticosterone (CORT; primary GC in amphibians) to physiologically relevant levels. We then measured immunity (neutrophil-lymphocyte ratios, plasma bacterial killing ability [BKA], skin microbiome, splenocytes, melanomacrophage centers [MMCs])  and overall health in newts following treatment with CORT or an oil vehicle control. Treatments were repeated for a short (2 treatments over 5 days) or long (18 treatments over 26 days) time period. Contrary to our predictions, most immune and health parameters were similar for CORT and oil-treated newts. Surprisingly, differences in BKA, skin microbiome, and MMCs were observed between newts subjected to short and long-term treatments, regardless of treatment type (CORT, oil vehicle). Taken together, CORT does not appear to be a major factor contributing to immunity in Eastern Newts, although more studies examining additional immune factors are necessary.

The data and files pertain to Experiments 1 through 3 of the manuscript and are organized into 3 file lists:

1. Physiological & Immunological Data (Experiments 1 through 3)

The datasets were generated from the quantification of corticosterone in plasma samples (Experiments 1 through 3), and various immunological measures from blood and tissue samples (Experiment 3).  Bd data (initial and the change in Bd load) were generated from extracted DNA from skin swabs collected from captive salamanders in Experiment 3. qPCR analysis was used to quantify Bd infection loads (genomic equivalents, GE) initial and the change in Bd load. To complement these data, an additional data file was generated from the quantification of corticosterone and cortisol in plasma samples collected from salamanders not used in Experiments 1, 2, or 3.

2. Skin Microbiome (Experiment 3)

The dataset was generated from extracted DNA from skin swabs collected from captive salamanders in Experiment 3. Specifically, sequenced DNA was processed in QIIME2 v2021.8, then used for analysis of alpha and beta diversity metrics in R (version 4.0.2) and IBM SPSS Statistics software version 27. 

3. Final Bd load (Experiment 3)

The dataset was generated from extracted DNA from skin swabs collected from captive salamanders in Experiment 3. qPCR analysis was used to quantify Bd infection loads (genomic equivalents, GE) at the end of the experimental period. Many salamanders cleared Bd infections (final infection load = 0 GE) resulting in zero-inflated data. To address this, these data were analyzed in R (version 4.2.2) using zero-inflated gamma regression models.

Qiime2 v2021.8, R version 4.0.2 and 4.2.2 (https://www.R-project.org) and IBM SPSS Statistics software version 27 (IBM, Corp, Armonk, New York, USA).