Regulation of host defense reaction gy parasitoid

当寄生在合适的寄主上时，寄生蜂的卵和幼虫都能避免寄主的防御反应。本项目分析了假蝇- cotesiakariyai系统中卵和幼虫未被寄主血膜包裹的原因。为了观察寄生后葡聚糖微球作为外来物注入寄主体内对其包封能力的影响。产卵后，丝粘胶珠周围包被层厚度随产卵天数的增加而减小。其厚度的减少似乎取决于两个原因：血细胞数量的减少或受体血细胞识别外来物质的改变。但由于血细胞数量的完全减少，易被细菌感染，使拟寄生虫处于不利地位。总血细胞计数表明，寄生后1天内血细胞数量减少至未寄生寄主的1/5，并一直保持到寄生蜂出现。寄生寄主体内血细胞数量的短期减少是由寄生寄主在产卵时注射多dna病毒和毒液引起的。人工注射多核酸病毒和蛇毒均可在注射后1小时内引起血细胞数量减少。玻璃板上附着的血细胞与异物封装处理有关。随排卵天数的增加，附着的血细胞数量也减少。寄生后随着时间的推移，经parcoll梯度分离的血细胞片段中粒细胞减少。在体外培养系统中，注射前6 h用多dna病毒和毒液预处理的血细胞难以包被涂有毒液的葡聚糖珠。这些结果表明，在卵期，被毒液包裹的卵很难被区分为异物。同时，多dna病毒和dna病毒的作用使血细胞数量减少

Both eggs and larvae of parasitoids can avoid defense reaction of hosts when parasitization occurred in suitable host. In this project, the reason why eggs and larvae are not encapsulated in the hemocoel of host was anslysed in Pseudaletia-Cotesiakariyai system. To examine the change of the ability of encapsulation by parasitization, Sephadex beads as foreign substance were injected into hosts. Thickness of encapsulation layr around Sephadex beads decreased with lapse of days after oviposition. Its decreasing thickness seems to depend on two causes : decreasing of number of hemocytes or change of receptor hemocytes to discriminate the foreigh substances. However, completely depression of number of hemocytes made the parasitoid disadvantage because of easy infection by bacteria. Counting of total hemocyte made clear that number of hemocytes decreased to 1/5 compared with one of unparasitized hosts in one days after parasitization, was maintained until emerge of parasitoid. Decreasing the number of hemocytes for a short term in parasitized host was caused by both polydnavirus and venom, which was injected into the host at the time of oviposition. Artificial injection of both polydnavirus and venom caused reduced number of hemocytes within 1 hr post-injection. Attached hemocytes on glass plate were so related with processing of encapsulation against foreign materials. Number of attached hemocytes was also decreased with lapse of days after oviposition. A fewer granulocyte in hemocyte fraction separated by parcoll gradient was observed with lapse of days after parasitization. Sephadex beads coated with venom were hard to be encapsulated by hemocytes preconditioned with polydnavirus and venom 6 h before injection in in vitro incubation system. These results suggested that during egg stage, eggs coated with venom was hard to be distinguished as foreign substance. Additionally, at the same time, the number of hemocytes was decreased by the function of both polydnavirus an