The Effect Of Sublethal Tebufenozide And Diapause On The Immunity Of Ostrinia Furnacalis (Guenée)

Ecological immunology is a newly established subject that concerning the effects ofenvironmental factors on the immunity of organisms. Its core idea is trade-off, whichinvolve how the ecological factors regulate the immune system, such as balance thecellular immunity and humoral immunity; and the balance of immune system and otherssystems, namely energy system. Recently, researches of ecological immunology based onthe invertebrate system increase rapidly. They have illuminated some effects ofenvironmental factors, such as temperature, light, host genotype, pathogen genotype, onthe immunity of host. Accordingly, my study explores how the insecticides and diapauseaffect the immunity of insect using the Asian corn borer (ACB) as a model insect.1. Immune response and transgenerational immune priming of ACB afterimmune challengeThe heat killed Escherichia coli and Ringer’s solution was injected into the hemocoelof ACB larvae, the larvae not injected were set as control. The hemocytes density andphenoloxidase activity and lysozyme activity were assayed12hours after injection. Theresults showed there were no differences of hemocytes density and phenoloxidase (PO)activity between immune challenged and not challenged larvae. However, lysozymeactivity did not observed in unchallenged larvae, but it showed a high level in challengedlarvae. The results manifests that immune challenge may not change the hemocytes leveland phenoloxidase activity, but induce the antimicrobial peptides and lysozyme.I further tested the in vitro antimicrobial activity of eggs produced by immunechallenged and unchallenged individuals. Results showed almost half of the egg mass hadantimicrobial activity except those laid by unchallenged individuals. This meanstransgerational immune priming also presented in ACB.2. The effect of tebufenozide on the development and immunity of ACBIndividuals treated with sublethal dose of tebufenozide had a lower pupa weight, butan equal pupa duration when compared with untreated individuals. Immune challenge alsohad a simillar effect on both tebufenozide treated and CK larvae. An interactive effectbetween tebufenozide and immune challenge reduced the pupa duration.After insecticide treatment, the constitutive immune components increased. Thehigher PO activity and hemocytes density were observed in insecticide treated individuals.I further used alive bacteria E. coli to challenge the insecticide treated and non-treatedlarvae and tested its bacterial tolerance and resistance. Results shows insecticide treatedlarvae has a higher survival rate and equal cleaning rate of E. coli, indicating highertolerance but equal resistance capability. 3. The effect of diapause on the immunity of ACBI compared the constitutive immune parameters of diapause and non-diapause. Therewas no difference of hemocytes density between two groups of individuals. The total POactivity was higher in non-diapause group, but the active PO was on the same level in twogroups. After immune challenge, the active and total PO activity were higher innon-diapause individuals. The hemocytes density are not different between diapause andnon-diapause group. Importantly, lysozyme activity are significantly higher in diapausegroup. Another surprising finding was the decreasing of the PO activity after immunechallenge in the diapause group.I compared the bacterial tolerance of diapause and non-diapause group by injectingalive E. coli and Bacillus thuringiensis into the hemocoel of larvae. The survival rate arehigher in diapause larvae when either treated with E. coli or Bacillus thuringiensisindicating a higher tolerance capability in diapause larvae.