Effect of precocene II on fatty acid metabolism in the pea aphid, Acyrthosiphon pisum, under cold stress

Pea aphids, Acyrthosiphon pisum (Harris), reared at 10 °C contain higher levels of fatty acids than those reared at 25 °C. This is primarily the result of an accumulation of triacylglycerols containing myristic acid. When aphids reared at 25 °C were transferred to 10 °C there was a gradual increase in triacylglycerol content that reached a maximum at 16 days post-transfer. Treatment of aphids with precocene II prior to transfer to 10 °C blocked the accumulation of fatty acids including myristic acid. A single application of 2 μg precocene II/aphid or two applications of 0.5 μg precocene II/ aphid administered on consecutive days resulted in aphids moved to 10 °C maintaining the same fatty acid profile as aphids maintained at 25 °C. Aphids that were treated with precocene II and maintained at 25 °C did not show changes in fatty acid profiles. Rearing aphids at 10 °C resulted in lower rates of reproduction and lower total numbers of progeny with longer longevity. Treatment with precocene II significantly decreased the total number of progeny produced at both temperatures. Precocene II did not reduce life span of aphids reared at 25 °C, however, the life span of treated aphids reared at 10 °C was decreased. The mechanism by which precocene II prevents the accumulation of myristic acid in aphids reared at 10 °C remains to be determined.