THE GROWTH AND ROLE OF MICROPLITIS-DEMOLITOR TERATOCYTES IN PARASITISM OF PSEUDOPLUSIA-INCLUDENS

The growth and function of Microplitis demolitor teratocytes in Pseudoplusia includens larvae was investigated. An average of 542 teratocytes was produced per M. demolitor egg. The number of teratocytes present per host declined during the course of parasitoid development, but the size of individual cells increased. The ploidy levels of teratocytes ranged from 2 to 8C at hatching, but had increased to 128-256C at the completion of parasitoid development. Injection of in vitro cultured teratocytes into fourth stadium P. includens larvae had an inconsistent effect on development. Most larvae pupated without delay when injected with a physiological dose of 600 teratocytes, but 54% of larvae failed to pupate when injected with a superphysiological dose of 2400 teratocytes. Examination of teratocytes indicated most cells were encapsulated by P. includens haemocytes within 24 h of injection. However, prior injection of larvae with M. demolitor calyx fluid or polydnavirus plus venom suppressed the encapsulation response. Further, 87% of larvae injected with polydnavirus plus venom and 600 teratocytes exhibited alterations in growth that were very similar to parasitism by M. demolitor.