ULTRASTRUCTURE OF MICROPLITIS-CROCEIPES (CRESSON) (BRACONIDAE, HYMENOPTERA) TERATOCYTES

The developing embryo of the braconid, Microplitis croceipes (Braconid ae : Hymenoptera), is encased in an extraembryonic serosal membrane. H atching of the parasitoid within the larva of its habitual host, Helio this virescens (Noctuidae Lepidoptera), is initiated about 40 hr after oviposition when held at 25 +/- 2-degrees-C. At this time, the monola yered serosal membrane begins to dissociate into individual cells (ter atocytes). After dissociation, teratocytes become dispersed in the hem olymph of the host. The average number of teratocytes released from ea ch parasitoid embryo is 914 +/- 43. Teratocytes average 14.1 +/- 2.4 m um in diameter when first released, and reach a maximum average diamet er of 68.1 +/- 4.6 mum 6 days after liberation. Newly released teratoc ytes have ovoid nuclei, simple mitochondria and a limited number of pr ofiles of the endoplasmic reticulum, all of which indicate relative me tabolic inactivity. The ramified nuclei, extensive endoplasmic reticul um, polymorphic mitochondria and accumulation of glycogen granules and lipid droplets observed in older teratocytes provide circumstantial e vidence that protein synthesis is occurring. Within hours after dissoc iation, microvilli begin to cover the surface of the teratocytes. Anat omical deformation (blebs) that occurred on some older (8-day-old) ter atocytes probably resulted from enlargement or expansion of microvilli .