Compensatory growth partially mediates the effects of stressors associated with climate change on amphibian physiology

Human-induced climate change and urbanization are predicted to
dramatically impact landscape hydrology, which can have devastating
impacts on aquatic organisms. For amphibians that rely on aquatic
environments to breed and develop, it is essential to understand how the
larval environment impacts development, condition, and performance later
in life. Two important predicted impacts of climate change and
urbanization are reduced hydroperiod and increased larval density. Here we
explored how larval density and hydroperiod affect development,
morphology, physiology, and immunity at metamorphosis and 35 days post
metamorphosis in the frog Rana pipiens. We found that high density had a
large negative impact on development and morphology, which resulted in
longer larval periods, reduced likelihood of metamorphosis, smaller size
at metamorphosis, shorter femur-to-body length ratio, and reduced
microbiome species evenness compared to animals that developed in
low-density conditions. However, animals from the high-density larval
conditions experienced compensatory growth post-metamorphosis,
demonstrating accelerated growth in body size and relative femur length
compared to animals from the low-density treatments. We also saw an
increase in relative gut length and relative liver size in animals that
had developed in the high-density treatment, as well as increased immune
function, and greater jump distances relative to their leg length across
different temperatures, which further supports post-metamorphic growth
compensation following a stressful developmental period. Finally,
metabolic rate was higher overall but especially at higher temperatures
for animals that developed under high-density conditions. A higher
metabolic rate at warmer temperatures might indicate a reduced ability to
acclimate quickly to increasing environmental temperatures.