PARASITIC CASTRATION OF PSEUDALETIA-SEPARATA BY COTESIA-KARIYAI AND ITS ASSOCIATION WITH POLYDNAVIRUS GENE-EXPRESSION

Parasitization by the endoparasitoid Cotesia kariyai caused the inhibi tion of spermatogenesis of Pseudaletia separata. This phenomenon is ca lled parasitic castration. The degree of castration was dependent on t he host stage parasitized. Host parasitized on day 1 of the 4th stadiu m (the time of primary spermatocyte accumulation), had testicular cell s with abnormal chromosomes appearing two days after parasitization, a nd spermiogenesis was completely inhibited. However, when hosts were p arasitized on day 0 of the 6th (final) stadium, the degree of castrati on was less severe, and elongated cells appeared similar to those foun d in nonparasitized larvae. Results of this study involving injection of C. kariyai polydnavirus (CkPV) and venom suggested that these wasp components caused the appearance of abnormal chromosomes in specific g erm cells, which were in mitotic or meiotic prophases. The amount of C kPV gene expression in host testes increased immediately after parasit ization and reached a maximum 12 h later. The early-expressed CkPV gen e(s) may be related to the parasitic castration phenomenon. (C) 1998 E lsevier Science Ltd. All rights reserved.