Variations in glycerol content and its influence on cold hardiness in the Alaskan carabid beetle, Pterostichus brevicornis

Quantitative paper chromatographic determinations of glycerol content in the haemolymph of adult P. brevicornis have revealed seasonal variations in the concentration of this substance. Mean glycerol concentrations in excess of 22 g% have been measured during winter with the values decreasing to less than 1 g% during spring and summer. Acclimation studies gave similar results. In the artificially warmed winter beetles glycerol content decreased to less than 1 g% within 36 hr at 20°C. Glycerol concentrations were closely correlated with the changing supercooling points and haemolymph freezing points in both the naturally acclimatized and laboratory acclimated specimens. Temperature preferences showed a positive correlation with changes in cold tolerance.