Effects of contrasting relative humidities on the cold tolerance of an Antarctic mite

Samples of adult Alaskozetes antarcticus, an Antarctic cryptostigmatid mite, were collected in winter and summer. In 4 separate experiments, mites were maintained under relative humidities in the range: 0, 26, 42, 55, 86 and 100% at 4°C. Changes in cold hardiness (measured as supercooling points, body water contents, cryoprotectants and percentage survival) and live weights were monitored for up to 93 days. Under saturated conditions, winter-collected mites showed a gradual loss of cold hardiness; with increased supercooling points, and substantial loss of glycerol. For mites kept in dry conditions (<55% r.h.), glycerol levels were relatively high, and supercooling points remained mainly unchanged, despite large decreases in live weight and body water content. Under desiccating conditions, glycerol accumulation was directly related to the rate of water loss. For summer-collected mites, rapid increases in cold hardiness occurred as a result of starvation, but the extent of these increases was proportional to the saturation deficit: i.e. supercooling ability increased most under the driest conditions. These findings are discussed in relation to theories concerning the relative proportions of bound and bulk water, and support the hypothesis that potential nucleators are present throughout the year in such freezing-susceptible species.


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Authors: Cannon, Raymond J.C.

1 January, 1986
Journal of Insect Physiology / 32
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