| Heavy metal pollution has become one of the most important global environmental problems.Cadmium and zinc are common heavy metal pollutants.Cadmium does not exist alone in the environment,and it usually causes mixed pollution with zinc and lead.Heavy metals in the environment are easily absorbed by animals or plants and transmitted via the food chain,As an important component of the food chain,there is little research about the effects of complex heavy metal stress on insects.In this study,Spodoptera litura was treated with zinc,cadmium or zinc-cadmium respectively.Effects of different heavy metal stress on the growth and hormones of S.litura were studied.The results are as follows:1?Effects of Zn,Cd and Zn-Cd combined stress on growth and development of S.lituraZn,Cd and Zn-Cd combined stress significantly prolonged the larval duration of S.litura.The weight of female pupae increased under Zn stress,while the weight of male and female pupae decreased under other heavy metal treatments.Cd and Zn-Cd combined stress significantly inhibited adult emergence,while Zn stress had no significant effect.Zn,Cd and Zn-Cd combined stress all increased the proportion of female adults,but there was significant difference between zinc stress and control.There was no significant difference between male and female adults' longevity and control under single stress of Zn and Cd.Under the combined stress of Zn-Cd,the life span of males was significantly shorter than that of control.Under Zn stress,the spawning duration is prolonged and the spawning quantity is increased.Cd stress has no significant effect on spawning duration,but it led to the decrease of spawning quantity.Under the combined stress of Zn-Cd,the duration of spawning and the number of spawning decreased significantly.It decreased by 33%and 52%respectively.2?Effects of Zn,Cd and Zn-Cd combined stress on endogenous hormones of S.lituraZn stress significantly increased the titer of juvenile hormone in 3 and 5 day-old male and female adults,while molting hormone titers only increased significantly in 3 and 5 day-old male adults.Under Cd stress,the titer of JH in 1 day-old female adults decreased significantly,but increased significantly at 3 day-old.The titers of JH in male adults of 3 day-old and 5 day-old were significantly increased.MH was significantly increased in 3 day-old female and 5 day-old male adults.The titers of JH in 5 day-old female adults and 3 day-old and 5 day-old male adults were significantly increased under the combined stress of Zn-Cd.MH only increased significantly in 3 and 5 day-old male adults.In the control group,the titers of JH and MH in female moths were higher than those in male moths.After heavy metal stress,the titers of JH and MH in male and female moths showed irregular changes.3?Effects of Zn,Cd and Zn-Cd combined stress on the activities of key enzymes in endogenous hormone synthesis and metabolic pathway of endogenous hormoneThe effects of Zn-Cd combined stress on the activities of key enzymes(FaMeT,JHE,JHEH,JHDK,CYP450)in endogenous hormone synthesis and metabolism pathway are different at different ages of adults.(1)Zn stress significantly increased FaMeT activity in 5 day-old male and female adults.Under Cd stress,FaMeT activity increased significantly in 3 day-old male and female adults and 5 day-old male adults,but decreased significantly in 5 day-old female adults.Under the combined stress of Zn-Cd,it increased significantly in both 3 day-old female adults and 5 day-old male and female adults.(2)Under Zn stress,JHDK activity increased significantly in 3 day-old male adults and decreased significantly in 5 day-old male adults.JHEH activity increased significantly in 1 day-old female and 3 day-old male adults,and decreased significantly in 5 day-old male and female adults.JHE activity decreased significantly in 3 and 5 day-old male adults.Under Cd stress,JHDK activity increased significantly in 1 and 5 day-old female adults.JHE activity increased significantly in 1,3,5 day-old female adults and 5 day-old male adults,and decreased significantly in 3 day-old male adults.Under the combined stress of Zn-Cd,JHDK activity increased significantly in 1 day-Old female,3 day-old male and 5 day-old male and female adults.JHE activity decreased significantly in 3 day-old male adults and increased significantly in 5 day-old female adults.JHEH activity increased significantly in 1 day-old male and female adults,and decreased significantly in 3 day-old male and 5 day-old male and female adults.(3)Under Zn stress,the activity of CYP450 decreased significantly in 1 and 5 day-old female adults,while increased significantly in 3 day-old female adults and 1,3,5 day-old male adults.Under Cd stress,the enzyme activities of female adults decreased significantly on the 1st day,while increased significantly in 1 day-old male,3 day-old female and 5 day-old male adults.Under the combined stress of Zn-Cd,the enzyme activities of 1 and 5 day-old female adults decreased significantly,while those of 3 day-old female adults and 1,3,5 day-old male adults increased significantly.4?Effects of Zn,Cd and Zn-Cd combined stress on expression of related genes in endogenous hormone synthesis and metabolic pathway of S.lituraCombined stress of Zn-Cd affected the expression of related genes(FaMeT,JHEH,JHDK,Dib,Sad,Phm)in the pathway of endogenous hormone synthesis and metabolism.(1)Under Zn stress,the expression of FaMeT was significantly up-regulated in 5 day-old male adults.Cd stress significantly increased the expression of male and female adults on the 3rd and 5th day.Zn-Cd combined stress was significantly up-regulated only in 5 day-old male adults.(2)Under Zn stress,JHDK was significantly down-regulated in 3 day-old female adults and up-regulated in 3 day-old male adults.JHEH was significantly down-regulated only in 5 day-old male adults.Under Cd stress,JHEH and JHDK were significantly down-regulated in 3 day-old female adults.JHDK was significantly up-regulated in 5 day-old female adults.Under the combined stress of Zn-Cd,only JHDK was significantly up-regulated in 3 day-old male adults.(3)Zn stress significantly increased the expression of Phm and Dib in 3 day-old male and female adults,while Sad was only significantly increased in 3 day-old male adults.The expression of Phm and Sad was significantly down-regulated in 5 day-old female adults.Sad and Dib were significantly upregulated only in 5 day-old male adults.Under Cd stress,the expression of Phm in 3 day-old female adults and Sad in 5 day-old male adults were significantly up-regulated.The expressions of Phm,Sad and Dib were significantly up-regulated under the combined stress of Zn-Cd.In conclusion,the combined stress of zinc and cadmium will adversely affect the growth,development and reproduction of S.litura.It will also affect the synthesis and metabolism of juvenile hormone and ecdysone in adults.The results of this study provide a scientific reference for expounding the effects of complex heavy metal stress on population dynamics and reproductive regulation of S.litura. |
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