DEVELOPMENTAL-CHANGES IN TERATOCYTES OF THE BRACONID WASP COTESIA-CONGREGATA IN LARVAE OF THE TOBACCO HORNWORM, MANDUCA-SEXTA

The endoparasitic wasp Cotesia congregata develops in the hemocoel of larval stages of the tobacco hornworm, Manduca sexta. Teratocytes were released from the serosal membrane during hatching of the first insta r wasp larva at 2-3 days after oviposition; about 160 cells were relea sed per embryo, The cells increased in diameter from about 10 to >200 mu m prior to wasp emergence, Nascent microvilli, visible on the cell surface before hatching of the first instar larva, rapidly increased i n length and number following release of the cells, Irrespective of wh en the wasps were due to emerge, or how many parasitoids were present in the host, dramatic cytological changes occurred in the cells during the last instar of the host's development, Many of these morphologica l and ultrastructural changes were symptomatic of the cytological feat ures of degenerating or apoptotic cells, and large numbers of vesicles appeared interspersed amongst the microvilli. The nucleus developed e xtensive dentritic ramifications, and the chromatin condensed in large clumps on the inner nuclear membrane, At the final stages of the wasp s' development, the nucleus occupied the bulk of the interior of-the c ell, The cytoplasm gradually grew dramatically more electronluscent an d less granular, as did the nucleoplasm, which is also indicative of i mpending cell death, Following the parasites' emergence, many of the c ells underwent extensive blebbing of the cell surface, Teratocytes wit hin a host appeared heterogeneous with respect to their morphological appearance, Analysis of the proteins secreted by teratocytes in vitro following labelling with S-35-methionine showed that many (> 30) polyp eptides were synthesized de novo and secreted by the cells; some prote ins were clearly targeted for secretion, We presume that the cells lik ely secrete a large number of proteins in vivo as well as in vitro. (C ) 1997 Elsevier Science Ltd. All rights reserved.