The molecular and metabolic essentials for long-distance flight in insects

Summary The mechanism of long-distance flight in insects was investigated by comparing lipid mobilization and transport in gregarious- and solitary-phase locusts and in the American cockroach. Unlike the gregarious-phase locust, both the American cockroach and the solitary locust were unable to form low-density lipophorin (loaded with increased amount of diacylglycerol) even when injected with adipokinetic hormone (AKH). The cockroach fat body responded to AKH. However, not only does the American cockroach lack apolipophorin-III (apoLp-III) in the haemolymph, but the fat body contains only an extremely small amount of diacylglycerol and a relatively large triacylglycerol pool. By contrast, the solitary-phase locust had apoLp-III in the haemolymph, but the fat body was only one-seventh or less in weight of the fat body of the gregarious locust. Furthermore, the fat body of the solitary locust contains a very small amount of triacylglycerol (1/20 or less of that of the gregarious locust) with only a trace of diacylglycerol. It was concluded that in the American cockroach and the solitary locust, the stores of fuel in the fat body are insufficient to maintain prolonged flight.Abbreviations AKII adipokinetic hormone - apoLp-III apolipophorin III - HDLp high-density lipophorin - LDLp low-density lipophorin - LTP lipid transfer particle - MW molecular weight - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis