Effects of JH III and JH analogues on phase-related growth, egg maturation and lipid metabolism in Schistocerca gregaria females

Abstract

Adult growth, egg maturation, fat body development and the strength of the adipokinetic reaction triggered by flight have been determined in laboratory-bred gregarious and solitary female Schistocerca gregaria. The body weight in young, maturing solitary females was higher than in gregarious ones. Egg maturation, i.e. vitellogenin synthesis, vitellogenin incorporation into the terminal oocytes and oocyte growth, started earlier in solitary than in gregarious females. Fecundity was also higher in solitary females. However, the proportion of fat body content and strength of the adipokinetic reaction were much higher in gregarious females, which is seen as a prerequisite for long-distance migratory flights. JH III and JH analogues were applied to newly emerged gregarious females. JH III and JH analogues induced egg maturation soon after application; in the case of fenoxycarb and BASF 228743 even much earlier than in control solitary females. The latter JH analogues also increased fecundity. JH III and JH analogues inhibited fat body development and suppressed the adipokinetic reaction. Thus they may suppress migratory flights. A possible employment of JH analogues in alternative locust control is discussed. JH III and JH analogues had an effect on the fatty acid composition of the haemolymph 1,2-diacylglycerols. The treatment increased the proportion of the polyunsaturated fatty acids. The effects of JH III and JH analogues on gregarious locusts are interpreted as solitarization effects. The role of JH in phase-related lipid metabolism and egg maturation is discussed. Our results are consistent with the hypothesis proposed for migratory insects, that migration and the underlying physiological processes are facilitated by low and female reproduction by high JH titres.