Ultrastructural studies on spermatogenesis in a parthenogenetic type of Paragonimus westermani (Kerbert 1878) proposed as P. pulmonalis (Baelz 1880).

Spermatogenesis in a parthenogenetic type of P. westermani (Kerbert 1878) called P. pulmonalis (Baelz 1880) throughout this study, was observed by light microscopy (LM), scanning (SEM), and transmission (TEM) electron microscopy. During spermatogenesis, most of the cells became degenerated or malformed as a result of aberrations during spermatogenesis. Vacuolated cells were often found in the testicular lumen. In some nuclei of spermatocytes, synaptonemal complexes were formed and this indicated that some pairing of homologous chromosomes did occur, but only rarely. Cytophores in some rosettes were broken down into small fragments and the cells separated from each other. Norman spermatozoa were very rarely found in the testis and never in the seminal receptacle, where egg and vitelline cells were present instead. Throughout spermatogenesis, Golgi complexes, mitochondria, ribosomes, and endoplasmic reticulum were not abundant, and this suggested that cell activities and protein synthesis were greatly reduced.