Abstract: 【Aim】 This study aims to clarify the utilization of energy substances in flight muscles of Bactrocera dorsalis (Hendel). 【Methods】 The activities of five key enzymes related to energy metabolism in flight muscles of B. dorsalis, i.e, glyceraldehyde phosphate dehydrogenase (GAPDH), glycerol-3-phosphate dehydrogenase (GDH), lactate dehydrogenase (LDH), citrate synthase (CS) and 3-hydroxyacyl-CoA dehydrogenase (HOAD), were assayed and analyzed by tethered flight testing and biochemical methods in the laboratory. 【Results】 The activities of the five enzymes assayed changed with age (day-old) of B. dorsalis adults. The activities of GAPDH, GDH, LDH and CS peaked in the 4-day-old adults, while the HOAD activity peaked in the 20-day-old adults. During tethered flight, the activities of GAPDH, GDH and CS showed similar change trend, gradually increasing with tethered flight duration, while the activities of LDH and HOAD showed distinctively different change trend between male and female adults. The LDH activity in female adults during tethered flight was lower than that of female adults in resting state, while that in male adults was just the opposite except the 2 h tethered flight treatment. The HOAD activity in male adults fluctuated above the resting state level except the 24 h tethered flight treatment, while that in female adults fluctuated between the resting state level and below.【Conclusion】 Energy substrates in flight muscles of B. dorsalis include carbohydrate and lipid, but carbohydrate metabolism provides primary energy. During tethered flight, significantly different energy metabolisms exist between male and female adults. Both aerobic and anaerobic metabolisms are present in flight muscles of male adults, but only aerobic metabolism is present in female adults. Male adults can utilize lipids as energy substrate for flight, but female adults hardly utilize lipids as energy substrate for flight. Our study provided a scientific basis for further illuminating the mechanisms of the migratory behavior of B. dorsalis.

Key words: Bactrocera dorsalis, flight muscle, tethered flight, energy metabolism, enzyme activity