Effects of low temperatures on the fatty acid composition of Hepialus jianchuanensis larvae

The larvae of Hepialus insects are the host of Ophiocordyceps (Berkeley) Saccardo with extreme cold- tolerance. The fatty acid composition of the whole caterpillar was determined by gas chromatography- mass spectrometer (GC- MS) after the sixth instar larvae of Hepialus jianchuanensis were exposed to low temperatures. The result indicated that the contents of total lipids and unsaturated fatty acids (UFAs) were increased, while the content of saturated fatty acids (SFAs) were decreased. The ratios of UFAs to SFAs were increased from 1.13 to 1.40 with temperature reduction. In addition, the linolenic acid (0.59-0.91%) was induced in the larvae after treatment of low temperatures, -3°C and 0°C. The regular changes in the fatty acid composition may result from their self-adaptation to the low-temperature environment.