Prasitism of Lacanobia oleracea (Lepidoptera) by the Ectoparasitic Wasp, Eulphus pennicorni, Disrupts the Cytoskeleton of Host Haemocytes and Suppresses Encapsulation In Vivo

摘要

Parasitism of Lacanobia oleracea larvae by the ectoparasitic wasp Eulophus pennicornis suppreassed host haemocyte-mediated encapsulation of Sephadex DEAE A-25 beads in vivo. Beads dissected out of parasitized larvae had fewer haemocytes associated with them. Moreover, those haemocyte that were associated with the beads tended to retation a rounded configuration and rarely flattened. Similar results were obtained using in vitro encapsulation assays. SDS PAGE indicated that for parasitized and PBS injected larvae, these were some differences in the plasma proteins that boudn to Sephadex DEAE A-25 beads, suggesting that parasitism-mediated changes to host plasma proteins might contribute to the differences in the encapsulation response occurring in these larvae. However, in vitro encpsulation assays using beads that had been pre-incubated in plasma from parasitized and unparasitized larvae,demonstrated that major differences in the extent of encapsulation did not occur. These results, plus in vitro haemocyte attchement and spreading assays, suggest that parastism-mediated suppression of encapsulation is primarily due to reductions in the ability of host haemocytes of actin in the haemocyte cytoskeleton by FITC-labelled phalloidin, which indicated that parasitism disrupts the formation of stress fibers and focal adhesions in plasmatocytes. By contrast, experimental injection of adult female wasp venom into unparasitized L. Oleracea larvae had no significant effect on in vivo encapsulation responses or the haemocyte cytoskeleton. Arch. Insect Biochem. Physiol.