菜蛾盘绒茧蜂多分DNA病毒的特性及其对小菜蛾幼虫的生理效应

对菜蛾盘绒茧蜂Cotesia plutellae多分DNA病毒的特性及其对寄主小菜蛾Plutella xylostella幼虫的生理效应进行了研究。结果表明：菜蛾盘绒茧蜂雌蜂输卵管萼中含有大量的多分DNA病毒（polydnavirus, PDV）；一个PDV内含多个核衣壳，最多可达16个；核衣壳长40～168 nm，直径39～40 nm；PDV仅在输卵管萼细胞内复制；雌蜂产卵时，随蜂卵将PDV注入寄主血腔，并扩散到寄主的许多组织中；PDV可能先通过脱膜再侵染寄主组织。雌蜂经Co⁶⁰辐射处理后再寄生（即假寄生）小菜蛾2龄、3龄和4龄初期的幼虫，被寄生后的寄主幼虫几乎全部不能化蛹，但末龄（即4龄）幼虫期显著延长，并在寄生后期，幼虫胸部有褐色的短翅芽出现；即将化蛹的4龄末小菜蛾幼虫被假寄生后，即使每头寄主被过寄生9次，依然能正常化蛹，但不能羽化。假寄生与正常寄生后寄主的脂肪体数量和形态结构有明显的不同，推测在正常寄生的情况下蜂卵孵化时释放的畸形细胞及随后的幼蜂可能对脂肪体的结构产生了作用。

Characterization of Cotesia plutellae polydnavirus and its physiological effects on the diamondback moth, Plutella xylostella larvae

The polydnavirus of Cotesia plutellae (Hymenoptera: Braconidae) was characterized and its physiological effects on the host larvae of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae) were studied in this paper. The results showed that the virion of polydnaviruses (PDVs) in the calyx region of female ovary had a tail and multiple nucleocapsids (up to 16) enveloped; the nucleocapsid measured 40-168 nm in length and 39-40 nm in diameter; PDVs replicated only in calyx cells that underwent lysis after replication completed; the calyx fluid was injected into the host larval haemocoel while female wasps laid eggs; large numbers of PDV virions were observed along the sheaths of the host tissues; it appeared that PDVs emerged from their envelopes first, and then infected the host tissues. When 2nd, 3rd and early 4th instar host larvae were parasitized by female wasps irradiated with Co⁶⁰ (resulting in pseudoparasitism), almost all of them were not able to pupate, but the period of the last instar larvae was significantly prolonged and a pair of brown short wing buds appeared on the thorax of host larvae at the end of the last instar; however, when host larvae of the late 4th instar were pseudoparasitized, and even if super-pseudoparasitized 9 times, they were still able to normally pupate, but not able to emerge. These results suggest that the PDVs and venom could prolong the developmental period of host larvae under conditions where there were no parasitoid eggs hatching, no teratocytes released and no parasitoid larvae present, but they seemed to have limited effect on the late 4th instar larvae. The numbers and micromorphology pattern of fat bodies of host larvae pseudoparasitized by the irradiated female wasps were distinctly different from those of normally parasitized hosts, suggesting that the teratocytes and parasitoid larvae may have some effects on the fat bodies of host larvae.