A conserved cold stress syndrome defines insect chill tolerance
The ability to withstand cold is arguably one of the most important traits defining the biogeographical distribution of insects. For most species, those classified as chill susceptible, cold tolerance is limited by the ability to maintain vital physiological functions at low temperature. However, there is currently no unified understanding of how physiological failure develops during cold stress…
Cold tolerance in insects is a crucial trait determining their distribution. While most species have limited cold tolerance, the exact mechanisms behind physiological failure during cold stress are unclear. Ion homeostasis disruption has been suggested to underlie chilling injury, but its role as a unifying physiological syndrome across different cold stress intensities and chill tolerance levels is uncertain.
To investigate this, researchers examined the relationship between cold mortality and hemolymph potassium ([K]) in Drosophila across varying cold stress intensities, 25 species with diverse cold sensitivity, biogeography, and phylogeny, and Drosophila melanogaster acclimated at different temperatures. They found that mortality was consistently associated with a specific cold-stress response: progressive hyperkalemia and death occurring when hemolymph [K] exceeded baseline by approximately 150% ([K]crit). This response was not influenced by adaptive or plastic variations in cold sensitivity.
Interestingly, the critical temperature (Tc) at which ion homeostasis failed explained adaptive and plastic variation in cold sensitivity among species. This framework, when applied to data from other insect orders, revealed remarkably similar [K]crit, suggesting that ionoregulatory collapse is a conserved physiological constraint defining insect cold survival.
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