| Helicoverpa armigera(Hübner)is a worldwide pest,which is widely damaged because of its wide host range and strong ability of survival and reproduction.With the change of planting structure and climate,the control of cotton bollworm has changed from the main control of larvae to the control of both larvae and adults.Starvation is a stress factor for cotton bollworm,which affects its life activities,especially its reproductive ability,and will be related to the reproduction of its offspring.Therefore,studying the effect of starvation on the reproduction of will help to systematically understand the fitness under starvation.In this study,the growth,development and reproduction under starvation stress in different developmental stages were observed,and the fitness under starvation stress were studied.At the same time,observe the development of eggs at different levels by dissecting the ovaries,record the fresh weight of ovaries and the length of ovarian tubes,and clarify the influence mode of adult starvation on ovarian development.This study also measured the juvenile hormone,triglyceride,glycogen,protein and other substances after starvation stress,and systematically analyzed the changes of juvenile hormone and energy substances under starvation stress.The main results of the study are as follows:1.The longer the starvation time in the larval stage of cotton bollworm,the greater the impact on the growth and development of the larva.The development time of 4th instar larvae starved for 1 d,2 d and 3 d were prolonged by 1.73 d,5.3 d and 6.22 d respectively.After 3 d of starvation,there were significant differences in pupal duration and pupal weight compared with the control.The pupal duration was shortened by 1.72 d and the pupal weight was reduced by 10.71%.The development time of 5th instar larvae was prolonged by 0.96 d,2.53 d and 5.11 d after starvation for 1,2 and 3 d,respectively.Compared with the control,the pupal duration was significantly prolonged by 2.39 d after 3 d of starvation,and the pupal weight decreased by 15.57%.With the prolongation of starvation time in larval stage,the oviposition of females decreased continuously.After 3 d of larval starvation,the oviposition reached the lowest,which were 277.29 ± 62.13 and 328.65 ± 45.65 respectively,which decreased by 65.21% and 58.76% respectively compared with the control.In addition,the pre-oviposition period of females was prolonged by larval starvation.After 3 d of starvation of 4th and 5th instar larvae,the pre-oviposition period of females was significantly prolonged by 0.43 d and 0.58 d,and the oviposition period was shortened by 2.78 d and 3.85 d respectively.The life span of adults was shortened after starvation treatment of 4th and 5th instar larvae,but there was a significant difference between the 4th instar larvae and the control,while the 5th instar larvae had no significant effect on the life span.After the normal death of females,the percentage of females who experienced starvation whose ovarian development level did not reach level V increased,and the number of unlaid eggs in the ovary was less than that in the control.There was no significant difference in the hatching rate of eggs between treatments and the control.2.After starvation treatments,there was no significant effect on the number of eggs laid by adults,which was 986.58 ± 33.28.The pre-oviposition period of females was prolonged by starvation,and the oviposition period and life span were shortened with the prolongation of starvation,but there was no significant difference.Starvation in adult stage reduced the hatching rate of eggs,but had no significant effect.Starvation for 1 d in adult stage had no significant effect on the survival rate of females,and the survival rate after starvation for 2d and 3 d was significantly lower than that of the control.After dissecting the dead females,it was found that the number of eggs left in the body was more after 1 d and 2 d of starvation,while the number of eggs left in the body decreased after 3 d of starvation.It was found that the number of level III mature eggs in the living ovary decreased after starvation for 1,2 and3 d,while re-feeding after starvation was conducive to the formation of mature eggs.The length of ovarian tube was shortened by 13.57%,15.78% and 13.74% after starvation for 1,2 and 3 d,respectively.After 3 d of starvation,the proportion of ovary decreased significantly,14.78% compared with the control.The number of mature eggs in the control female decreased significantly and the ovarian tube contracted,while starvation delayed the time of laying a large number of eggs,resulting in the number of mature eggs and the length of ovarian tube in the starvation treatment group on the fourth day being higher than that in the control.3.Double starvation treatment had a great impact on the fecundity and survival rate of female,resulting in a 71.56% reduction in oviposition and a significant reduction in survival rate compared with the control.Compared with the control,the pre-oviposition period of females was significantly prolonged by 0.73 d after double starvation.Compared with the control,the spawning period and life span of females were significantly shortened by 5.65 d and 6.44 d.Dissecting the normal dead females after double starvation treatment,it was found that the number of eggs left in the body was 69.83% lower than that in the control.After starvation treatment in different developmental stages,the order of reproductive indexes is as follows: oviposition: control > adult starvation > larval starvation > double starvation,pre-oviposition: Double starvation > larval starvation > adult starvation > control,oviposition period and life span: control > adult starvation > larval starvation > double starvation,Through the comparison of the above reproductive indicators,it can be concluded that double starvation has a cumulative effect on the fecundity of females,which seriously affects the survival and reproduction of females.4.Starvation in larval stage and adult stage had no significant effect on the triglyceride content in the female,but double starvation had a cumulative effect,resulting in a significant decrease in triglyceride content in female,which decreased by 77.19% compared with the control.The glycogen content of adults decreased significantly after starvation for 2 and 3d,and decreased by 82.36% and 55.43% respectively compared with the control.After starvation for 3 d and feeding for 1 d,the content of glycogen increased by 56.10% compared with the control.In the starvation treatment at different developmental stages,the protein content increased by 27.88% and 21.02% respectively compared with the control.Starvation for 1,2 and 3 d in adult stage had no significant effect on protein content.5.The regulation mode of juvenile hormone under different starvation conditions is complex.3 d of larval starvation and 1 d of adult starvation have no significant effect on the titer of juvenile hormone in the female,while the titer of juvenile hormone after 2 and 3 d of adult starvation increased significantly by 124.02% and 324.34% compared with the control,respectively.After double starvation,the titer of juvenile hormone decreased significantly,66.53% compared with the control.By systematically comparing the effects of starvation treatments in different periods on the reproductive development and energy substances,it was found that starvation treatments in different periods had adverse effects on the fecundity.Among them,starvation in adult stage had less effect on the fecundity,starvation in larval stage had a greater effect on the fecundity,and the effects of common starvation in larval stage and adult stage on the reproduction had a cumulative effect,it seriously affects the survival and reproduction of female insects and the content of energy substances and juvenile hormone. |
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