| The magnetic field(MF) and electrical field(EF), as the environmental factor, has been significant influence on living beings. In recent years, MF has led to an overwhelming increase in the presence of electromagnetic fields(EMF) of a wide spectral range, which due to the industrial and household machines and appliances, high voltage power grids and medical devices, these radiations were only some of the products of modern material civilization that produce additional MF, and these fields exceed the natural presence of this factor by several orders of magnitude. The biological effects of living systems have been studied for many years under the exposure of magnetic fields and electrical field, however, living system show a variety of responses to electric fields are only associated with immediate effects, and in biomagnetics, a problem has arisen that is frequently seen in such rapidly developing fields: the difficulty of finding suitable systems for direct study of the phenomena, the magnetic effect on biological material is almost certain to be very small, if the biological system is so complicated as to mask the effect looked for. On the other hand, if the system is too simple, the sensitivity may be lost. Sitobion avenae(Homoptera: Aphididae) can be the good material of researching adaptation and evolution of insects as their biological characteristics of parthenogernesis and high fecundity; the armyworm, Mythimna separata(lepidopteran) can be as the materials of biological density pressure because of the density-dependent prophylaxis(DDP)The present study explore the short-term effects of magnetic field on the development and population parameters of Sitobion avenae, and the long-term effects of electrical field on the development, the activity of antioxidant enzymes and carboxylesterase(Car E), the DNA mutation;meanwhile, the functional regulation of insect cytokine growth-blocking peptide(GBP) in the density-dependent color change was investigated to explore the effects of the density pressure. The research results are as follows:1、The development, fecundity and population parameters of S. avenae were estimated after radiating the first instar nymphys by conyiuous 30 generation electrical field exposure in different dose(0 k V/cm, 2 k V/cm, 4 k V/cm,6 k V/cm). The results demonstrated that the age-stage specific survival rates(sxj) of 4 k V/cm were significantly lower than that of the control group using the binomial fitting equation. The population parameters of the intrinsic rate of increase(r), net reproductive rate(R0) were fluctuated as the increase of the exposure generation, but all of the exposure intensities were with the lowest intrinsic rate of increase(r) under the sixth generation. Therefore, the long-time exposure inhibits the development and fecundity of the S. avenae, and the 4 k V/cm and the sixth generation were the critical dose and stage for S. avenae.2、The effect on activity of antioxidant enzymes and carboxylesterase(Car E) of S. avenae were estimated under the exposure of electrical field for 30 generation consequently. The results showed that only the 4k V/cm were significantly difference among the generations. The activity of superoxide dismutase(SOD) and Car E were fluctuated but higher than that of the control group. The activity of peroxidase(POD) and catalase(CAT) were significantly lower than that of the control group but with the high activity in the sixth generation. The results indiacted that SOD and Car E were exhibited the mechanism of the protection and CAT and POD were restricted under the 4 k V/cm electrical field exposure. The most significant influence was occurred at the intensity of 4 k V/cm. The sxith generation was more sensitive for S. avenae.3、The analysis of SSR-PCR with enetic indentity and clustering analyzing showed that the genetic difference of S. avenae populations was signicant. The genetic toxic effects were observed after the thirty generation exposure: the NTSYS pc 2.1 software anlyasis showed that the lower electrical field(2k V/cm) with the less genetic difference while the higher electrical field(6 k V/cm) with the higher genetic difference. However, the most significant diffence were observed in the medium electrical field(4 k V/cm).4、The development and population parameters of S. avenae were estimated after short-time radiating the first instar nymphys by 0.176 T and 0.065 T magnetic filed under four different periods(15 min, 30 min, 60 min, 120 min). The adult longevity, survival rate and the intrinsic rate of increase were lowest in 0.176 T-30 min and 0.065 T-60 min, respectively, what is more, the combination of the 0.065 T-60 min were lower than that of the 0.176 T-30 min. therefore, the toxic effects were showed in the short-time magnetic field exposure, and there is the interaction between the dose intensities and exposure periods, the combination of lower intensities-long period showed the more toxic effects than that the higher intensities-short period exposure.5、The magnetic hysteresis loop measurements in aphid S. avenae :the Hysteresis loop was closed in the 60000 Oe, and it showed that magnetic substance can be detected existing in adult aphid, which provide the material theory of the biological effects of magnetic field on S. avenae.6、Cuticular melanization is one of the forms of phase polyphenism in lepidopteran insects in which the expression of a variety of traits can be affected by local population density. We tested for the expression of density-dependent cuticular melanization in the armyworm, Mythimna separata. When reared at high densities, the larvae exhibited darker cuticular melanization than larvae reared at low densities. The functional regulation of insect cytokine growth-blocking peptide(GBP) in the density-dependent color change was investigated. It demonstrated that the gene expression of GBP in armyworm increased with the population density of larvae. In order to confirm further regulation mechanisms of GBP in cuticular melanization, we used direct injection of protein GBP into the body of larvae and compared the difference of cuticular melanization before and after the treatments, and found the body color of armyworm injected GBP was darken than that of the control injected the Ringer’s solution.In summary, the present study includes that the electrical field exerts the long-term significant effects on the development, enzyme actives and gene variation of the Sitibion avenae; the magnetic field show the biological effects on the development and Hysteresis loop of the Sitibion avenae. It concludes that Sitibion avenae can be the good material of researching adaptation and evolution of insects as the biological effects of electromagnetic biological effecs, and it also explores the research range of the electrical and magnetic biological effects. |
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