Effects Of Simulated Change In Geomagnetic Field Intensity On The Growth,Development,Reproduction And Behavior Of Brown Planthopper(Nilaparvata Lugens) And The Respective Mechanisms

Organisms(including migratory insects)on the earth are constantly affected by the geomagnetic field(GMF).The migratory insects can have a long distance migration,and there is a perceptible difference in the GMF intensity between the emigration and immigration regions,which affects the population fitness of migratory insects.This study was carried out to clarify the magnetobiological effects on migratory insect populations so to help predict the occurrence of migratory insect pests.In this paper,the brown planthoppe,Nilaparvata lugens,was taken as the research object,and the direct current Helmholtz coil was used to simulate the geomagnetic field environment of the migratory pests of the imigration regions(Guangzhou:GMF45μT)and the emigration regions(Nanjing:GMF50μT).The effects of changes in the magnetic field intensity of the emigration regions andimmigration regions on its development,reproduction and behaviour.The results are as follows:1.Population fitness of N.lugens in response to the change of geomagnetiv field intensityThe simulated change in geomagnetic field(GMF45 μT vs.GMF50 μT)significantly affected the egg hatching rate and egg duration of N.lugens,and there were significant differences between generations.In addition,it significantly affected the longevity of females adults of N.lugens.There was significant differerce in body weight between male and female adults.The results showed that in the immigration region(GMF50 μT),the egg duration of N.lugens was slightly shortened(0.50%),the egg hatching rate was significantly enhanced(6.11%),the developmental duration of female and male nymphs was lengthened by 5.26%and 2.37%,respectively,the body weight of the newly hatched female and male adults was increased by 0.66%and 9.56%,respectively,and the developmental duration of female and male adults was shortened by 35.34%and 26.15%,respectively,as compared with those in the emigration region(GMF 45 μT).Moreover,the fecundity of female adults was significantly enhanced(30.13%)and the relative transcription level of Vg was significantly enhanced(259.25%).Furthermore,compared with the GMF intensity 45 μT,the GMF intensity 50 μT significantly decreased the egg duration(2.52%)and significantly increased the egg hatching rate(10.83%)of the F1 generation of N.lugens.The results suggest that the GMF intensity of the region where N.lugens is located after northward migration in spring is positive for its migration to enhance the population fitness,further advantageous for the population occurrence and increasing the risk of population outbreak and damage in the immigration regions in spring.2.Effects of simulated change in geomagnetiv field intensity on wing differentiation and the phototaxis of N.lugensThe simulated change in geomagnetic field(GMF45 μT vs.GMF50 μT)significantly affected the wing-type differentiation ratio,positive phototaxis and expression of magnetoreception-related multifunctional genes cryptochromes(i.e.Cryl and Cry2)and IscAl(i.e.MagR)of female and male adults of N.lugens.Compared with the GMF45 μT of Guangzhou,the macropterous ratio of male and female adults of N.lugens increased significantly(+75.85%and+17.60%)under the GMF50 μT of Nanjing.Compared with the macropterous female adults,the ratio of macropterous males increased significantly(+50.80%and +127.50%)under GMF50 μT and GMF45 μT.In addition,the positive phototaxis of male and female adults of N.lugens significantly decreased(-30.03%and-14.09%).Further studies found that the simulated change in geomagnetic field intensity significantly affected the magnetoreception-related multifunctional genes cryptochromes(i.e.Cryl and Cry2)and IscAl(i.e.MagR).Compared with the GMF45 μT,the GMF50 μT significantly reduced expression level of Cry1 on the2nd and 3rd day(-34.66%and-54.42%;P<0.05),Cry2 on the 2nd day(-71.26%;P<0.05)and MagR on the 1st day(-43.73%;P<0.05)in females,this result is consistent with the change of positive phototaxis,in addition,it also significantly decreased the expression level of Cry1 on the 1st and 3rd day(-17.31%and-4.53%;<0.05),Cry1 on the 3rd day(-112.26%;P<0.05)in males,and significantly increased the expression level of MagR on the 3rd day(+54.72%;P<0.05)in males,it can be seen that the decrease of positive phototaxis is related to the expression of cryptochrome gens(Cry1 and Cry2),but not consistent with the expression of MagR.The results showed that the northward migration in spring,with the increase of geomagnetic field intensity,the ratio of macropterous male and female adults of N.lugens increased,thus increasing the migrating population;in addition,the down-regulation of the expression of key genes of magnetoreception leads to the decrease of the positive phototaxis of macropterous female and male adults,which is reduces the proportion of migratory populations,which is not conducive to migtation and diffusion of N.lugens.3.Effects of simulated change in geomagnetic field intensity on flight and energy materials of macropterous N.lugensThe simulated change in geomagnetic field(GMF45 μT vs.GMF50 μT)had significant sex dferernce on the flight distance of macropterous N.lugens,and there was interaction between GMF and sex;meanwhile,the contents of trehalose and trehalase in the macropterous adult of N.lugens were significantly affected.The results showed that compared with GMF45μT,the flight distance of macropterous male adult of N.lugens was significantly prolonged(+38.84%)and the flight distance of macropterous female adult of N.lugens was shortened(-24.04%),,and the activity of trehalase in the N.lugens was decreased(-4.57%),and the content of glucose and triglyceride were significantlt increased(+39.86%and+123.33%)under the GMF50 μT treatment.In addition,compared with macropterous females,the trehalose content of macropterous males decreased(-58.07%and-24.59%),while the trealase activity of macropterous males significiantly increased(+127.48%and+137.27%)under the GMF45 μT and GMF50 μT treatment.The results showed that the female and male adults used different energy materials during the northward migration of N.lugens in spring,which led to the difference of migration distance.It was speculated that the magnetic field migration range of N.lugens was smaller with the increase of magnetic field intensity.It’s not good for its migration and diffusion.4.Analysis of N.lugens transcripts under simulated change in geomagnetic field intensityThe simulated change in geomagnetic field(GMF45 μT vs.GMF50 μT)for transcriptome analysis of 2d female N.lugens,GO classification of the DEGs(OBF/BF)and KEGG classification of Unigenes in the transcriptomes of newly emerged adult females showed that energy metabolism,protein synthesis and signal transduction related pathways were significantly enriched in N.lugens under the change of geomagnetic field intensity,which indicated that these genes played an important role in the resopnse of N.lugens to the change of geomagnetic field intensity.