Effects Of Juvenile Hormone On Reproduction And Longevity In Helicoverpa Armigera, And On The Development Of Its F₁Generation

Ultraviolet (UV) is a kind of important environmental stress factors, under UV exposure there are trade-offs between reproduction and longevity in the phototactic insect, Helicoverpa armigera. Hormones mediate the physiological responses of organisms to changes, which is the important regulator of life history. In insect, Juvenile hormone is one of the most important hormones, and plays a key role in regulating of metamorphosis, growth and reproduction. Therefore, here, we choose cotton bollworm as experimental material, the effects of the JHa on female adult reproduction and longevity as well as the development of the F1generation in H. armigera are investigated. The main results are as follows:(1) Effect of JHa on the female adult reproductionAmong the different concentrations of JHa0.1μg/2μL,1μg/2μL,5μg/2μL,10μg/2μL. Application of JHa yielded significant effects on the female adult reproduction. The mean total number of eggs laid per female adult increased first, then decreased with JHa concentrations increasing. Lower concentrations of JHa significantly increased the fecundity, but high concentrations had no significant effect, and tended to show some inhibitoey; the effect of JHa on female adult ovarioles development of H.armigera was similar to the effect on fecundity, JHa stimulates the reproduction by stimulating ovarioles development, the effect on fecundity mainly concentrate in the short days about four days after injection, and exogenous JHa stimulates the reproduction of H.armigera in a dose-dependent manner. The results showed that in insect, the effect of JHa on different physiological processes had sensitive period and different threshold.(2) Effect of JHa on the female adult longevityApplication of different concentrations of JHa yielded significant effects on the female adult longevity. Female adult longevity decreased gradually with JHa concentrations increasing. Lower concentrations of JHa (0.1μg/2μL and1μg/2μL) had no significant effect on female adult longevity, whereas significant decrease was observed in groups treated with higher concentrations (5μg/2μL and10μg/2μL)(P=0.035). (3) Effect of JHa on the development of the F1generationJHa does not significantly stimulate egg hatch, larval and pupal survival of the F1H. armigera, high dose (10μg/2μL) JHa causes a remarkable decline in pupal survival, and significantly lowers the cumulative survival of F1immature stages, however the other concentrations have no significant effect; but the developmental periods of F1larvae differ between intermediate dose (1μg/2μL and5μg/2μL) groups and control group. When adults are treated with intermediate concentrations JHa, F1larvae take shorter time to reach the pupal stage, but the groups treated with0.1μg/2μL and10μg/2μL JHa, the developmental periods of the F1larvae is still at control level; between the treatment and control groups, the developmental periods of F1pupae do not differ. The results suggest that the effect of JHa still exists in the F1generation of H. armigera. In conclusion, all of JHa treatments decrease survival rate and accelerate development of the F1generation.