Abstract: Parasitic castration often takes place in host insects parasitized by endoparasitoids. Using the morphological method and protein technology, we studied the effects of parasitization on the testicular development of Plutella xylostella parasitized by Oomyzus sokolowskii Kurdumov (Hymenoptera: Eulophidae), Diadegma semiclausum Hellén (Hymenoptera: Ichneumonidae) or Cotesia plutellae (Kurdj.) (Hymenoptera: Braconidae), respectively. The results showed that neither the testicular appearance and structure of the host larvae, nor the content and categories of proteins extracted from its host testes changed compared with the control when the host larvae were parasitized by O. sokolowskii. However, when parasitized by D. semiclausum, the testicular development of P. xylostella larvae was adversely affected with deformed nuclei and condensation of chromatin observed in germ cells, but some elongated sperms could still come into being in the testes of parasitized larvae; the content of proteins in a pair of testes decreased significantly after parasitization, but the constitution of proteins had no alteration compared with that of the control. The most pronounced parasitic castration was observed in the host larvae parasitized by C. plutellae, spermatogenesis in the parasitized larvae was inhibited completely, many degenerated testicular cells and the debris of sperm were found in the atrophic testes, and the content of total proteins in these testes sharply declined. Furthermore, SDS-PAGE profiles of testicular total proteins revealed that a protein of an approximate molecular mass of 63.4 kD was absent in testes of P. xylostella larvae parasitized by C. plutellae compared with the non-parasitized host larvae.

Key words: Endoparasitoids, Oomyzus sokolowskii, Diadegma semiclausum, Cotesia plutellae, Plutella xylostella, spermatogenesis, parasitic castration