Regulation of host defense reaction gy parasitoid

当寄生在适宜的寄主上时，卵和幼虫都能避开寄主的防御反应。本课题研究了伪盘绒茧蜂-Cotesiakariyai系统中卵和幼虫不被包裹在宿主血腔中的原因。将葡聚糖凝胶珠作为外源物质注入宿主体内，观察寄生后包囊能力的变化。产卵后，葡聚糖凝胶珠周围的包裹层厚度随时间的推移而减小。其厚度的减少似乎取决于两个原因：一是血细胞数量的减少，二是受体血细胞的变化，以区分外来物质。但血细胞数量的完全抑制使寄生蜂处于不利地位，易被细菌感染。血细胞计数表明，寄生后1天内血细胞数下降至未寄生寄主的1/5，并一直维持到寄生蜂羽化。寄生后宿主血细胞数量的短期减少是由多DNA病毒和产卵时注入宿主体内的毒液共同引起的。人工注射多脱氧核糖核酸病毒和毒液引起注射后1小时内血细胞数量减少。玻璃板上粘附的血细胞与包封处理有关。产卵后，随着时间的推移，附着的血细胞数量也减少。随着寄生后天数的增加，通过parcoll梯度分离的血细胞组分中的粒细胞减少。在体外孵育体系中，用多DNA病毒和蛇毒预处理6 h的血细胞很难包被蛇毒包被的葡聚糖凝胶。这些结果表明，在卵期，卵被毒液包被很难被鉴别为异物。此外，同时，多脱氧核糖核酸病毒和

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