Characteristics of a developmental arrestant in the venom of the ectoparasitoid wasp Euplectrus comstockii

Abstract

Parasitic Hymenoptera regulate their hosts in order to provide a suitable source of nutrition and dwelling for their offspring. Few regulatory factors known to cause a specific effect on the host have been structurally characterized. The larval ectoparasitoid Euplectrus comstockii Howard (Hymenoptera: Eulophidae) arrests larval-larval ecdysis in its lepidopteran hosts. Prior to oviposition, the female wasp injects a venom into the hemocoel of the host and that venom alone is effective in causing the arrestment. A venom gland-reservoir structure connected to the lower reproductive tract of the wasp contains a complex mixture of proteins. There are no obvious similarities among the electrophoretic banding pattern (native or denatured) for venom proteins of E. comstockii and several other parasitic hymenopteran species. Venomous protein, separated by electrophoretic techniques, with a native mol. wt of c. 66,000, was capable of arresting larval-larval ecdysis in 4th instar larvae of Trichoplusia ni (Lepidoptera : Noctuidae). Nanogram quantities of the protein were sufficient to cause arrestment. The activity of the protein was sensitive to temperature, pH, organic solvent, and protease.