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Snow flies self-amputate freezing limbs to sustain behavior at sub-zero temperatures

Golding, Dominic1; Rupp, Katie1; Sustar, Anne1; Pratt, Brandon1; Tuthill, John1

Research facility: University of Washington
Published Nov 07, 2023 on Dryad. https://doi.org/10.5061/dryad.7sqv9s4xz

Data files

Abstract

All living things are profoundly affected by temperature. In spite of the thermodynamic constraints on biology, some animals have evolved to live and move in extremely cold environments. Here, we investigate behavioral mechanisms of cold tolerance in the snow fly (Chionea spp.), a flightless crane fly that is active throughout the winter in boreal and alpine environments of the northern hemisphere. Using thermal imaging, we show that adult snow flies maintain the ability to walk down to an average body temperature of -7 °C. At this supercooling limit, ice crystallization occurs within the snow fly’s hemolymph and rapidly spreads throughout the body, resulting in death. However, we discovered that snow flies frequently survive freezing by rapidly amputating legs before ice crystallization can spread to their vital organs. Self-amputation of freezing limbs is a last-ditch tactic to prolong survival in frigid conditions that few animals can endure. Understanding the extreme physiology and behavior of snow insects is important at this moment when the alpine ecosystems they inhabit are rapidly changing due to anthropogenic climate change.