Cold-Tolerance Mechanisms of the Antarctic Nematode<i>Panagrolaimus Davidi</i>

Abstract

ABSTRACT When free of surface water in air or liquid paraffin, the antarctic nematode Panagrolaimus davidi is freezing intolerant but avoids freezing by supercooling. Survival of long-term exposure is enhanced by sub-zero temperatures compared with controls maintained at 99% relative humidity and 15 °C. In water the nematodes are seeded by exogenous ice nucleation and a proportion are freezing tolerant. Ice formation appears to be restricted to the pseudocoel. The degree of freezing tolerance is dependent upon the age of the culture and its thermal history. P. davidi is freezing tolerant when exposed to sub-zero temperatures in water and freezing intolerant when free of surface water and able to supercool. These two strategies are not mutually exclusive as they are often thought to be in arthropods.