Effects Of Near-Zero Magnetic Field On Development,Reproduction And Flight Behavior In Mythimna Separata(Walker)

Geomagnetic field,as the basic physical factor on the Earth,affects the development and evolution of all living things on the earth at all time.Mythimna separate,a typical long-distance migratory pest,show group migration and common orientation behavior during migration.M.separata go back and forth from North Chian to South China every year,causing great harm to China’s crop yield.Studies have shown that the M.separata may orienteed by percive the magnetic field cue.In order to further explore the mechanism of the M.separata response to magnetic field changes,clarify the biological magnetic sensory mechanism,provide new strategies and technologies for biological control,this article takes the M.separata as the research object and the change of the magnetic field intensity as the environmental impact factor to clarify the effect of near-zero magnetic field on growth and development,stability of reference genes,and the transcriptome respons of M.separata..The main results are as follows:1.With the M.separata as the research object,we explored the biological effect of the near-zero magnetic field on the growth and development of M.separata to gain sight to the adaptive strategy of M.separata to the magnetic field varities.The experimental results show that,compared with the normal geomagnetic field,the near-zero magnetic field has no significant effect on the hatching durations and hatching rates of eggs of M.separata,but significantly prolongs the larvae development durations by 1.3d(P<0.01)and pupa development durations by 0.2d(P<0.01);the near-zero magnetic field significantly reduces the pupa weight of M.separata.The longivity of male moths was significantly prolonged by 1.7d(P=0.003).The longivity of female moths was reduced but not reached a significant level under the near-zero magnetic field(P>0.05).In addition,the near-zero magnetic field had no significant difference in the reproduction of female moths(P>0.05),but significantly reduced the relative expression level of the vitellogenin(Vg)gene in newly emerged females(P<0.01).Moreover,the mating rate of M.separate under the near-zero magnetic field was significantly reduced by 10.03%(P <0.01).2.The influence of near-zero magnetic field on the flight ability of M.separata was clarified by using the flying mill system.The near-zero magnetic field significantly reduced the average flight speed and distance of adult M.separata,and the percentage of long-distance flying M.separate was reduced.An insect autonomous flight test system developed by our laboratory was used to Identify the effects of near-zero magnetic fields on the free-flight of M.separata.Results show that near-zero magnetic field has a certain effect on the flight rhythm of M.separata.The total flight activites of adult M.separata show a apparent but nonsignificant decreased during the 12 h test period in near-zero magnetic field.Under the near zero magnetic field,the peak of flight activity of the armyworm moth last about three hours,starting from 6-8 hours after dark,while the flight activity of the armyworm under normal geomagnetic field continued to increase to 9-10 h.At 9-10 h,the flying activity of M.separata under the near-zero magnetic field was significantly smaller than that under the normal magnetic field(P <0.05),indicating that the night-time magnetic rhythm of Mythimna separata under the near-zero magnetic field changed.3.A study was conducted on the newly emerged female M.separata,GeNorm、BestKeeper、Normfinder、Reffinder were used to study the stability of the reference gene of the female moth of M.separata.under different magnetic field conditions to selected suitable referrence gene for subsequent quantitative real-time PCR(qRT-PCR)experiments,which can provides a accuracy guarantee for the transcriptomics analysis of the magnetic response of M.separata.in the near-zero magnetic field.The experimental results show that under the near-zero magnetic field:β-Actin and 18 S are most stable in newly emerged female adults of M.separata.4.Analysis of the transcriptome of M.separata in the near-zero magnetic field revealed that compared with the local magnetic field,M.separata larvae had 439 differential genes in the near-zero magnetic field,of which 215 genes were up-regulated and 224 genes were down-regulated;1671 differential genes was identified in female moths,of which 545 were up-regulated and 1056 were down-regulated.1401 differential genes were identified in male moths,of which 545 were up-regulated and 856 were down-regulated.GO function enrichment of differential genes found oxidoreductase activity,DNA polymerase activity,G protein coupled receptor activity,cell development and growth,trehalose transport,immune response,chemical homeostasis,response to external biological stimuli in larvae,defensive response and other items were significantly enriched inlarvae.Catalytic and binding processes such as DNA metabolism,fatty acid metabolism,sulfur compound metabolism,eggshell formation,hydrolase,peptidase,and nuclease activity.In the male moth,DNA metabolism,enzyme activities,transposition,transferase,polymerase,peptidase,and nuclease were significantly enriched in female moths.Pathway functional enrichment analysis of different expression genes showed that pentose phosphate pathway was significantly enriched in larvae.Lysosomes,platelets,focal adhesion adenylate-activated kinase,extracellular matrix receptor interaction pathway,and pyruvate metabolism pathways were significantly enriched in female moth.The near-zero magnetic field may affect the activities of these proton(ion)transport and binding in the enzymes and proteins containing metal of the armyworm,and then affect the activity,structure and function of the enzymes and proteins,further affectinga series of physiological and biochemical reactions.