Sex-dependent latent chilling injury changes estimates of thermal tolerance in a model insect

Abstract

Thermal injury sets limits to ectotherm mobility and survival. These limits are frequently integrated into models describing or predicting climate suitability for species of interest. Cold stress severity, sex, and prior thermal acclimation status can all influence lower thermal limits. There is a growing understanding of how chilling injuries initially manifest, but despite reports of latent injury or repair that may happen after rewarming, we poorly understand these phenomena. We exposed male and female Drosophila melanogaster to an acute or chronic cold stress before assessing their mobility over a 24 h period. Females progressively worsened under both conditions, but male mobility neither worsened nor improved. Female mobility declined slower in flies recovering at cooler temperatures, and cold acclimation significantly mitigated latent injury in females following the same degree of initial injury, regardless of recovery temperature. We conclude that latent chilling injury can be sex-specific, occurs independently from mechanisms driving tissue damage in the cold, is temperature-dependent, and is mitigated by prior thermal acclimation. We argue that latent chilling injury and the factors that influence it should be more carefully considered in estimating tolerance limits.