COLD TOLERANCE AND DEHYDRATION IN ENCHYTRAEIDAE FROM SVALBARD

When cooled in contact with moisture, eight species of arctic Enchytra eidae from Svalbard were killed by freezing within minutes or hours at -3 and -5 degrees C; an exception was Enchytraeus kincaidi which surv ived for up to 2 days. When the temperature approached 0 degrees C the enchytraeids apparently tried to escape from the moist soil. The supe rcooling capacity of the enchytraeids was relatively low, with mean su percooling points of -5 to -8 degrees C. In contrast, specimens of sev eral species were extracted from soil cores that had been frozen in th eir intact state at -15 degrees C for up to 71 days. Compared to freez ing in a moist environment, higher survival rates were obtained during cooling at freezing temperatures in dry soil. Survival was recorded i n species kept at -3 degrees C for up to 35 days, and in some species kept at -6 degrees C for up to 17 days. Slow warming greatly increased survival rates at -6 degrees C. The results strongly suggest that arc tic enchytraeids avoid freezing by dehydration at subzero temperatures . In agreement with this, weight losses of up to ca. 42% of fresh weig ht were recorded in Mesenchytraeus spp. and of up to 55% in Enchytraeu s kincaidi at water vapour pressures above ice at -3 to -6 degrees C. All specimens survived dehydration under these conditions.