Cold acclimation and cryoprotectants in a freeze-tolerant Antarctic nematode, Panagrolaimus davidi

Panagrolaimus davidi is a freeze-tolerant Antarctic nematode which survives extensive intracellular freezing. This paper describes the development of culture techniques which provide clean samples, with a high degree of freez e tolerance and in sufficient quantities for the analysis of potential cryo protactants. Cultures grown at 20 degrees C survived a short-term freezing stress but survival declined with the time spent frozen. Acclimation of cul tures at 5 degrees C enhanced the long-term survival of freezing. Starvatio n, however, reduced the nematode's ability to survive short-term freezing. The principal cryoprotectants detected by gas chromatography were trehalose and glycerol. The levels of trehalose, but not those of glycerol, increase d significantly after acclimation, Trehalose may stabilise membranes and pr otect them against the dehydrating effects of the osmo tic stresses resulti ng from freeze concentration effects but other factors, such as recrystalli sation inhibition, may be involved in long-term survival.