Young mated male Caribbean fruit flies [Anastrepha suspensa (Loew)] have greater sexual prowess than their virgin counterparts. After mating for the first time, 6- to 7-day-old males released twice as much sex pheromone and acquired another mate in less than half the time required by virgin males of the same age. Mass spectroscopic analysis of extracts of hemolymph from mated and virgin 7-day-old males resulted in identification of juvenile hormone III bisepoxide and juvenile hormone III in a ratio of 2.5:1. Extracts from mated males contained 3-fold more juvenile hormone than did extracts from virgins. Enhancement of sexual signaling, pheromone release, and mating was induced by topical application of juvenile hormone, methoprene, or fenoxycarb. Newly eclosed adult males treated with juvenoids engaged in sexual signaling, released pheromone, and mated at significantly earlier ages than control males. We conclude that juvenile hormone mediated a positive feedback system that imparted a competitive advantage, guaranteeing that males who mated at an early age would out-compete virgins of the same age for mating opportunities. Additionally, the results support the hypothesis that juvenile hormone is a pivotal hormone coordinating the development of sexual signaling and reproductive maturity in these flies.
The sterile insect technique (SIT) may offer a means to control the transmission of mosquito borne diseases. SIT involves the release of male insects that have been sterilized by exposure to ionizing radiation. We determined the effects of different doses of radiation on the survival and reproductive capacity of local strains of Aedes aegypti and Ae . albopictus in southern Mexico. The survival of irradiated pupae was invariably greater than 90% and did not differ significantly in either sex for either species. Irradiation had no significant adverse effects on the flight ability (capacity to fly out of a test device) of male mosquitoes, which consistently exceeded 91% in Ae . aegypti and 96% in Ae . albopictus . The average number of eggs laid per female was significantly reduced in Ae . aegypti at doses of 15 and 30 Gy and no eggs were laid by females that had been exposed to 50 Gy. Similarly, in Ae . albopictus , egg production was reduced at doses of 15 and 25 Gy and was eliminated at 35 Gy. In Ae . aegypti , fertility in males was eliminated at 70 Gy and was eliminated at 30 Gy in females, whereas in Ae . albopictus , the fertility of males that mated with untreated females was almost zero (0.1%) in the 50 Gy treatment and female fertility was eliminated at 35 Gy. Irradiation treatments resulted in reduced ovary length and fewer follicles in both species. The adult median survival time of both species was reduced by irradiation in a dose-dependent manner. However, sterilizing doses of 35 Gy and 50 Gy resulted in little reduction in survival times of males of Ae . albopictus and Ae . aegypti , respectively, indicating that these doses should be suitable for future evaluations of SIT-based control of these species. The results of the present study will be applied to studies of male sexual competitiveness and to stepwise evaluations of the sterile insect technique for population suppression of these vectors in Mexico.
We have been studying the behavioural and physiological mechanisms associated with coordination of reproductive maturity and sex pheromone communication in male tephritid flies in order to develop methods for acceleration of reproductive maturity among sterilized males. Our studies revealed that exposure to the juvenile hormone analogue methoprene can accelerate the rate of sexual maturity in some but not all tephritid species tested. Additionally, we have determined that incorporation of protein hydrolysate into the adult diet improves sexual performance of sterile males. Coupling a diet enriched with protein hydrolysate for adult food and application of methoprene to adult males or pupae was found to advance significantly the age at which males of a number of species of flies from the genus Anastrepha and Bactrocera cucurbitae (Coquillet) become sexually mature and improve reproductive success of the males. These results have led to the development of a novel strategy to accelerate the reproductive development and increased competitiveness of mass‐reared fruit flies for use in the sterile insect technique by incorporating methoprene treatment and protein hydrolysate diets into protocols for fruit fly emergence and release facilities. The following reviews research conducted to develop the system and our suggestions for use in improving efficacy of mating by sterile males destined for release in programmes to control some species of tephritid flies using the sterile insect technique.
The sterile insect technique (SIT) has been used successfully for the control of fruit flies. The efficiency of this technique can be significantly reduced when sterile released insects are exposed to adverse conditions and predators, as a great number of sterile insects die before reaching sexual maturity and thus fail to mate with wild females. Treatments with juvenile hormone (JH) analogues such as methoprene (M) significantly reduce the time to reach sexual maturity by sterile Anastrepha ludens (Loew) (Diptera: Tephritidae) males. In this study, we compared the sexual performance of non‐treated sexually mature males with young males that had been sexually accelerated with M. Furthermore, we compared the ability of M‐fed males in inhibiting female remating compared with sexually mature males. Results showed that at 5 days M‐fed males had lower mating success than mature males; however, 6‐day‐old (0.1%) M‐fed males had the same amount of matings as mature 13‐day‐old males. Young 5‐ to 10‐day‐old M‐fed males also had similar number of matings as mature non‐treated 12‐ to 17‐day‐old males. There were no differences in copula duration between treatments. Moreover, there were no differences between the fertility, fecundity or refractory period of females mated with either young male fed M or normal sexually mature males. These results indicated that young males that were sexually accelerated with M have the same sexual performance as non‐treated sexually mature males. Implications of using M as a pre‐release treatment for A. ludens controlled through SIT are discussed.
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