Chilled, starved or frozen: insect mitochondrial adaptations to overcome the cold

Abstract

Physiological adaptations to tackle cold exposure are crucial for insects living in temperate and arctic environments and here we review how cold adaptation is manifested in terms of mitochondrial function. Cold challenges are diverse, and different insect species have evolved metabolic and mitochondrial adaptations to i) energize homeostatic regulation at low temperatures ii) stretch energy reserves during prolonged cold exposure, and iii) preserve the structural organization of organelles following extracellular freezing. While the literature is still sparse, our review suggests that cold-adapted insects preserve ATP production at low temperatures by maintaining preferred mitochondrial substrate oxidation, which is otherwise challenged in cold-sensitive species. Chronic cold exposure and metabolic depression during dormancy are linked to reduced mitochondrial metabolism and may involve mitochondrial degradation. Finally, adaptation to extracellular freezing could be associated with the superior structural integrity of the mitochondrial inner membrane following freezing which is linked to cellular and organismal survival.