Temperature drives physiological performance, disease expression and ecological interactions in freshwater ectotherms. For host-pathogen systems, warming can alter both host tolerance and pathogen dynamics, yet empirical tests of how thermal stress interacts with disease history at the population level remain unknown. Crayfish are keystone species and ecosystem engineers whose individual condition and performance can strongly influence community structure and ecosystem processes. In Montana, USA, lesion prevalence from Aphanomyces astaci, the oomycete responsible for crayfish plague, varies widely in Faxonius virilis populations.
We experimentally evaluated how warming temperature regulated physiological and behavioral stress responses in F. virilis originating from populations with contrasting plague expression histories (high versus low lesion prevalence). Individuals were acclimated to multiple temperature treatments and monitored for survival, molting success, lesion progression, growth and behavioral performance under thermal challenge. We found that short term survival was high across temperature treatments and did not differ strongly between crayfish from high and low lesion prevalence populations. Instead, temperature primarily influenced physiological performance, as acclimation history strongly shaped loss of righting response during thermal ramps, while lesion prevalence structured baseline lesion burden and recovery after exposure to thermal stress.
Considering that crayfish exert both strong top-down and bottom-up effects in freshwater ecosystems, temperature-disease interactions at the individual level may scale to influence community structure and ecosystem function under future climate scenarios.