Nakamatsu Y, Tanaka T, Harvey J A
Applied Entomology, Graduate School of Bio-Agricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
Arch Insect Biochem Physiol. 2007 Sep;66(1):1-8. doi: 10.1002/arch.20189.
Mature larvae of the gregarious endoparasitoid Cotesia kariyai construct cocoons for pupation approximately 10 days after parasitization and emerge from their host Pseudaletia separata under a long day photo-regime (16L8D) at 25 +/- 1 degrees C. The parasitoid larvae make capsules in the host hemocoel just prior to their emergence. These capsules function as "anchors," which enable them to press against the host integument from inside the host. It was predicted that this anchor might be composed of silk proteins secreted from the parasitoid larvae, because a previous study showed that the anchor was made up of a glycoprotein and that the silk gland of parasitoid larvae developed from 2nd larval stage. Fibroin-like proteins in C. kariyai larva mainly consist of two proteins with molecular masses of the 300.6 and 46.7 kDa estimated by SDS-PAGE. The fibroin-like proteins with the same molecular mass were detected from the anchor proteins just prior to parasitoid emergence. These results indicate that the anchor was assembled with fibroin-like proteins and was formed just before parasitoid emergence while in the host body cavity. Injection of bovine pancreatic trypsin inhibited the emergence of parasitoid larvae from the host because the anchor was decomposed by trypsin. Trypsin activity in the parasitized host hemolymph increased only after parasitoid emergence.
群居性内寄生蜂卡里亚侧沟茧蜂的成熟幼虫在被寄生后约10天结茧化蛹，并在25±1℃的长日照光周期（16小时光照8小时黑暗）下从寄主黏虫体内羽化而出。寄生蜂幼虫在羽化前会在寄主血腔中制造胶囊。这些胶囊起到“锚”的作用，使它们能够从寄主体内抵住寄主的体表。据推测，这个“锚”可能由寄生蜂幼虫分泌的丝蛋白组成，因为先前的一项研究表明，“锚”是由一种糖蛋白构成，且寄生蜂幼虫的丝腺从幼虫第二阶段开始发育。卡里亚侧沟茧蜂幼虫中的类丝心蛋白主要由两种蛋白质组成，通过SDS-PAGE估计其分子量分别为300.6 kDa和46.7 kDa。在寄生蜂羽化前，从“锚”蛋白中检测到了分子量相同的类丝心蛋白。这些结果表明，“锚”是由类丝心蛋白组装而成，并且是在寄主体腔内寄生蜂羽化前形成的。注射牛胰蛋白酶会抑制寄生蜂幼虫从寄主中羽化，因为“锚”会被胰蛋白酶分解。只有在寄生蜂羽化后，被寄生寄主血淋巴中的胰蛋白酶活性才会增加。
