RELATIONSHIP BETWEEN SUPERCOOLING CAPABILITY AND CRYOPROTECTANT CONTENT IN EGGS OF PARARCYPTERA MICROPTERA MERIDIONALIS (ORTHOPTERA: ACRYPTERIDAE).

ABSTRACT

BACKGROUND: Grasshoppers are major agricultural pests throughout the world. The egg stage is important for the low temperature resistance, and almost all grasshoppers overwinter in the egg stage. OBJECTIVE: To study the relationship between cold hardiness and cryoprotectant content in Pararcyptera microptera meridionalis eggs. MATERIALS AND METHODS: The supercooling point (SCP) of the eggs was measured, along with the contents of water, fat, amino acids, low molecular sugars and polyols. RESULTS: SCP, water content and glucose concentration decreased during egg development, whereas the contents of fat, trehalose, glycerol, inositol and sorbitol increased. SCP is negatively correlated with the concentrations of fat, trehalose, glycerol, inositol and sorbitol, but positively with water content and glucose concentration. Among low molecular weight sugars and polyols tested in eggs, trehalose concentration was highest, followed by glycerol. Although total content of free amino acids did not change much, of the tested 17 free amino acids in eggs, proline and glutamine had increased by 46.3 % and 13.2 %, respectively, and both showed a negative correlation with SCP. Stepwise regression analysis showed that proline, glycerol, trehalose and inositol contribute most to the SCP depression. Cold acclimation at 0 degree C increased the contents of trehalose and glycerol, and decreased SCP. CONCLUSION: The increase of the supercooling capacity in P. microptera meridionalis eggs during development could be attributed mainly to proline, glycerol, trehalose and inositol. Cold acclimation enhances supercooling capacity via glycerol and trehalose.