Morphology and Ultrastructure of Brain Tissue and Fat Body from the Flesh Fly,Sarcophaga bullataParker (Diptera: Sarcophagidae), Envenomated by the Ectoparasitic WaspNasonia vitripennis(Walker) (Hymenoptera: Pteromalidae)

Abstract

This study tested the hypothesis that venom from the ectoparasitic waspNasonia vitripennistargets brain tissue and fat body from its flesh fly host,Sarcophaga bullata. By 1 h postenvenomation, some brain neurons began to show irregularities in nuclear shape, and though they were predominately euchromatic, there was evidence of heterochromatin formation. Irregularity in the nuclear envelope became more prominent by 3 h after envenomation, as did the condensation of heterochromatin. The severity of ultrastructural changes continued to increase until at least 24 h after parasitoid attack. At this point, cellular swelling and extensive heterochromatic inclusions were evident, multivesicular bodies occurred in the cytoplasm of some cells, and the rough endoplasmic reticulum was dilated in many of the cells. Immunohistochemical staining revealed significant apoptosis in neurons located in brain tissues. By contrast, there was no evidence of any morphological or ultrastructural disturbances in fat body tissues up to 24 h after envenomation, nor did any of the cells display signs of cell death.