Simultaneous freeze tolerance and avoidance in individual fungus gnats, <Emphasis Type="Italic">Exechia nugatoria</Emphasis> |
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Authors: | Todd Sformo F Kohl J McIntyre P Kerr J G Duman B M Barnes |
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Institution: | (1) Institute of Arctic Biology, University of Alaska Fairbanks, PO Box 757000, Fairbanks, AK 99775-7000, USA;(2) Department of Mathematics and Statistics, University of Alaska Fairbanks, Chapman Building Room 101, Fairbanks, AK 99775, USA;(3) Plant Pest Diagnostics Branch, California State Collection of Arthropods, California Department of Food and Agriculture, 3294 Meadowview Rd., Sacramento, CA 95832, USA;(4) Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA |
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Abstract: | 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). |
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