ROLE OF GLYCEROL IN THE COLD-HARDENING OF BRACON CEPHI (GAHAN)

Abstract

Concentrations of glycerol as great as 5 molal are built up in larvae of Bracon cephi (Gahan) after hibernation begins in the fall, and are lost again in the spring. The source of the glycerol was not determined, but is not glycogen. Large solute concentrations, composed mostly of glycerol, depress the melting points of the haemolymph to as low as −17.5 °C. Supercooling points of the intact larvae are lowered even more than their melting points, and this excess is proportional to the melting point depression.Glycerol is directly responsible for the cold-hardening of the larvae in two separate ways: by increasing supercooling, it increases the ability of the larvae to avoid freezing, and by its protective action it allows the larvae to survive even if they do freeze.