Original Paper

Journal of Comparative Physiology B

, Volume 179, Issue 7, pp 897-902

First online:

Simultaneous freeze tolerance and avoidance in individual fungus gnats, Exechia nugatoria

  • Todd SformoAffiliated withInstitute of Arctic Biology, University of Alaska Fairbanks Email author 
  • , F. KohlAffiliated withInstitute of Arctic Biology, University of Alaska Fairbanks
  • , J. McIntyreAffiliated withDepartment of Mathematics and Statistics, University of Alaska Fairbanks
  • , P. KerrAffiliated withPlant Pest Diagnostics Branch, California State Collection of Arthropods, California Department of Food and Agriculture
  • , J. G. DumanAffiliated withDepartment of Biological Sciences, University of Notre Dame
  • , B. M. BarnesAffiliated withInstitute of Arctic Biology, University of Alaska Fairbanks

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Freeze tolerance and freeze avoidance are typically described as mutually exclusive strategies for overwintering in animals. Here we show an insect species that combines both strategies. Individual fungus gnats, collected in Fairbanks, Alaska, display two freezing events when experimentally cooled and different rates of survival after each event (mean ± SEM: −31.5 ± 0.2°C, 70% survival and −50.7 ± 0.4°C, 0% survival). To determine which body compartments froze at each event, we dissected the abdomen from the head/thorax and cooled each part separately. There was a significant difference between temperature levels of abdominal freezing (−30.1 ± 1.1°C) and head/thorax freezing (−48.7 ± 1.3°C). We suggest that freezing is initially restricted to one body compartment by regional dehydration in the head/thorax that prevents inoculative freezing between the freeze-tolerant abdomen (71.0 ± 0.8% water) and the supercooled, freeze-sensitive head/thorax (46.6 ± 0.8% water).


Mycetophilidae Exechia nugatoria Supercooling Exotherm