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

Abstract

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.

Current and time‐lagged effects of climate on innate immunity in two sympatric snake species

“…Lower immunity during dry years or years following dry years could be the result of a life‐history trade‐off, where investment in other factors such as reproduction or growth is being prioritized over physiological correlates of survival, such as immune function (Sheldon & Verhulst, 1996). Recent work in frogs ( Rana pipiens ), for instance, has shown evidence of trade‐offs between growth, survival, and immune function in the context of rapid pond drying (Brannelly et al., 2019). Alternatively, if resources are sufficiently limited during dry years, we might expect reduced investment in all measurable life‐history outcomes, such that individuals are not only suffering reduced immune function, but also experiencing reductions in other critical life‐history traits such as growth and reproduction.…”

Stress hormones mediate developmental plasticity in vertebrates with complex life cycles

“…Earlier reproductive maturity increases the proportion of individuals that survive to reproduce, and thus can substantially increase the population growth rate ( Birch, 1948 ; Cole, 1954 ) as well as individual fitness (greater lifetime fecundity) ( McGraw and Caswell, 1996 ). Tadpoles exposed to pond drying accelerated metamorphosis and metamorphosed at a smaller body size, which caused performance deficiencies in locomotion and immune function of juvenile frogs ( Brannelly et al, 2019 ; Sinsch et al, 2020 ). On the other hand, frogs from tadpoles reared in the presence of predators had longer limbs, which provide for better jumping ability to escape predators ( Emerson, 1978 ; Nicieza et al, 2006 ; Relyea, 2001a ; Van Buskirk and Saxer, 2001 ).…”

Susceptibility of frogs to chytridiomycosis correlates with increased levels of immunomodulatory serotonin in the skin

“…Photos of granular glands were taken with a microscope, at 20× magnification. Photos of glands were analysed for size and fullness, following Brannelly, Ohmer, Saenz, and Richards‐Zawacki using ImageJ (Schneider, Rasband, & Eliceiri, ). The protocol for measuring gland fullness consisted of fixing the photo white balance, outlining the gland, adjusting photo saturation and brightness, analysing the area within the outlined gland, and calculating the proportion full.…”