Effects of hydroperiod on growth, development, survival and immune defences in a temperate amphibian

The many and varied effects of human-induced environmental change have the potential to threaten animal biodiversity and species abundance. Importantly, human land use and global climate change are predicted to reduce water availability, which might have negative consequences for freshwater organisms. In this study, we tested for an effect of a shortened hydroperiod on larval growth and development, and post-metamorphic survival and immune function in a temperate frog, Rana pipiens. Animals developing under pond drying conditions metamorphosed at a smaller size and had lower survival after metamorphosis. We found sex-specific differences in larval period in our fastest drying treatment, with males metamorphosing more quickly than females. Individuals that developed under drying conditions also showed reduced skin swelling after phytohaemagglutinin injection, indicating a compromised immune response. We found support for trade-offs between growth, development and post-metamorphic immune function across hydroperiod treatments. Whole blood from animals with shorter larval periods had lower bacterial killing ability, and small-bodied juveniles had lower antibody titres. Overall, our results indicate that a shortened hydroperiod can affect the rate of larval amphibian growth and development, and might negatively impact the condition of species that rely on freshwater for development. Our work improves understanding of the complex impacts that environmental stressors might have on the health of animal populations. A free Plain Language Summary can be found within the Supporting Information of this article.