Life at the freezing edge

The fact that any small, cold blooded animal such as the insects can sustain temperatures below the freezing point of water has to be one of the most remarkable features of animal evolution. Even more impressive, the “snow fly” Chionea alexandriana is part of an elite group of insects that can maintain high levels of activity at sub-freezing temperature, and can often be spotted running on the snow-covered ground at temperatures between +3 and -5°C.

Image created by Sarah Becan for the Gallio Lab

To investigate the molecular adaptations that make this cold tolerance possible, we assembled the chromosome-length genome of the snow fly Chionea alexandriana. The assembly was created using a combination of PacBio HiFi and Hi-C sequencing from a a single male individual collected in the La Bohn Gap (47.55317, -121.24306). The work was supported in part by a grant from the Trienens Institute for Sustainability and Energy at Northwestern University (to Marco Gallio) and from the Crafoord foundation (to Marcus Stensmyr).

The analysis of the genome revealed several molecular adaptations including antifreeze proteins that prevent ice crystal formation, genetic pathways enabling cellular thermogenesis, and modifications to sensory and stress-response systems that enhance tolerance to extreme cold. You can read more about this work in

Capek M, Suhendra R, Yang Z, Omer AD, Weisz D, Dudchenko O, Tuthill J, Lieberman Aiden E, Kath WL, Para A, Stensmyr M and Gallio M. Coordinated molecular and physiological adaptations enable active behavior at subfreezing temperature in the snow fly Chionea alexandriana. Current Biology. 2026. https://doi.org/10.1016/j.cub.2026.02.060

Explore the interactive Hi-C contact map for the snow fly below, and check out the assembly page for more details and fasta links.