Abstract
Overwintering larvae of the rice stem borer, Chilo suppressalis obtains freezing tolerance to about -25℃ by the accumulation of glycerol in the haemolymph and replacing water with glycerol in the cell through the water channel during freezing. Moreover, when fat body tissue was frozen with an inhibitor of the water channel, the degree of freezing injury in overwintering larvae was significantly lower than that in non-diapausing larvae. In the present study the qualitative and quantitative changes of phospholipids in the last instar larvae of the rice stem borer were examined in summer and winter. Results showed that the total amount of their phospholipids did not change significantly between summer and winter and that the sum of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) comprised about 85% of their total phospholipids. In summer, the ratio of the PE to PC was almost one, while from autumn to mid winter it increased and reached three in February. The fatty acid compositions of PC hardly changed, and their percentage of unsaturated fatty acids did not exceed 50%. In contrast, the percentage of unsaturated fatty acids of PE in overwintering larvae increased up to 80% as ambient temperatures fell and oleic acid mainly contributed to the high percentage of unsaturation.
