Larvae of the European corn borer (Ostrinia nubilalis Hubn.) were cold acclimated during different phases of diapause to determine if changes in the fatty acid composition lipids occur as part of a programmed diapause strategy, or as a response to low temperatures during winter. Cold acclimation of fifth instar larvae of O. nubilalis during diapause had modest effects further on the readjustments in fatty acid composition of triacylglycerols and phospholipids. Overall, FA unsaturation (UFAs/SFAs ratio) was stable, with the exception of the triacylglycerols fraction after exposure to -3 and -10 °C in mid-diapause (MD) when it significantly increased. Differential scanning calorimetry (DSC) was used to examine phase transitions of total body lipid of cold-acclimated larvae in diapause. Thermal analysis indicated that changes in the melt transition temperatures of whole body total lipids were subtle, but consistent with the modest changes in the level of FA unsaturation observed. We conclude that lipid rearrangements are a function of the endogenous "diapause program" rather than a direct effect of low temperatures, which proved to have limited impact on lipid changes in diapausing larvae of O. nubilalis.
Keywords: Cold acclimation; Fatty acid composition; Lipid melt transition temperatures; Ostrinia nubilalis; Phospholipid; Triacylglycerol.