Coping with the longest winters in the world: Energetics in an Antarctic insect

The long, cold winters in polar regions provide unique energetic challenges for the insects that live there. The Antarctic midge, Belgica antarctica, is the only endemic insect in Antarctica, and it must accumulate sufficient energy during a short growing season (~3-4 months) to fuel overwintering metabolism, support energetically demanding molecular responses to environmental stress, and provide fuel to resume activity and development when conditions are favorable. Here, we present several factors that influence the energy budget of B. antarctica. First, terrestrial Antarctic features dramatic environmental heterogeneity in its habitats, and fine-scale variation in microclimate (primarily temperature) drives variation in energy accumulation and expenditure during the growing season. In addition, overwintering energy use is strongly influenced by temperature; experimental winter warming of only 2°C led to significant energy depletion, suggesting that the increasingly warming winters in Antarctica may be detrimental for terrestrial insects. Lastly, the stress responses needed by B. antarctica to cope with its harsh terrestrial environments are energetically costly. In previous work we demonstrated that recovery from acute ecologically relevant stressors is energetically demanding in the short-term, and in ongoing work we are determining whether stress responses incur long-term costs. Given the short growing season and the inability of B. antarctica to feed as an adult, energetically costly repair processes may have permanent fitness consequences. Together, our work indicates that survival in Antarctica is energetically challenging, and additional work is needed to fully characterize the energy budget of Antarctic insects in relation to rapidly changing environmental conditions.