Meeting Abstract
Climate change is increasing environmental temperatures and droughts around the world. Many tropical anurans lay terrestrial eggs, relying on environmental moisture for embryonic development. These eggs are vulnerable to dehydration, which may alter development or cause mortality. However, in some species, embryos can hatch prematurely to escape from drying eggs. Although warm temperatures can accelerate hatching by speeding development, it is unknown if embryos also respond behaviorally to warming, showing a voluntary thermal maximum (VTMax) at which they leave the egg. Further, it is unknown if embryo VTMax depends on hydration. We used a warming experiment to evaluate if Agalychnis callidryas embryos hatch early as an immediate behavioral response to high temperatures. We discovered that these embryos make a behavioral escape-hatching decision to avoid excess warming, showing a VTMax. Second, we examined if hydration level of eggs and egg-clutch jelly influence the response of embryos to warming. We found the hatching response varies with hydration state. Fully hydrated eggs and clutches warmed substantially slower than dehydrated ones, suggesting hydration buffers embryos from environmental warming via evaporative cooling. Moreover, embryos tolerated higher temperatures before hatching if they were initially well-hydrated. Our results demonstrate a convenient behavioral assay for thermal tolerance of terrestrial anuran embryos and reveal interacting effects of dehydration and high temperatures at an early life stage.
