Osmotic stress effects on the freezing tolerance of the antarctic nematodePanagrolaimus davidi |
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Authors: | D A Wharton N B To |
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Institution: | (1) Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand, Fax: +64-3/479-7584, e-mail: david.wharton@stonebow.otago.ac.nz, NZ |
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Abstract: | The freezing and freezing survival of the Antarctic nematode Panagrolaimus davidi after exposure to solutions of different osmotic concentrations has been examined using a thermoelectric cooling stage and
multi-specimen cooling block to see if there is any evidence that freeze-induced desiccation prevents inoculative freezing.
The nematodes froze in all the test solutions used (up to 1138 mosmol ⋅ l-1) and at all cooling rates and nucleation temperatures tested. Freezing survival was at its maximum in 0.1 mol ⋅ l-1 NaCl in artificial tap water after 1 h exposure to the test solution and in artificial tap water after 24 h exposure. Hyperosmotic
and hyposmotic stress adversely affected the nematodes’ ability to survive freezing. In non-frozen controls survival declined
with increasing osmolality of the test solution. Measurements of the osmolality of water extracted from a variety of moss
samples indicate that the nematodes are exposed to an osmotic concentration of about 9 mosmol ⋅ l-1 in their natural habitat. This is close to that of artificial tap water. Our experiments, and measurements of freeze concentration
effects in the literature, indicate that freeze-induced desiccation is unlikely to prevent inoculative freezing and the survival
of nematodes over the winter.
Accepted: 5 May 1996 |
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Keywords: | Freeze-induced desiccation Inoculative freezing Moss Osmolality |
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