Abnormal spermatogenesis in the common liver fluke (Fasciola sp.) from Japan and Korea.

Diploid and triploid specimens of Japanese and Korean Fasciola sp. showed abnormality in their spermatogenesis. Live germ cells obtained from the testes were observed under a differential interference contrast microscope. In the stages from spermatogonium to spermatid, the cells combined together at the central cytoplasmic bridge during a series of divisions. One spermatogonium becomes a cell group of 8 primary spermatocytes through 3 mitoses. Until the primary spermatocyte stage, cells are divided in a uniform manner. In most of the diploid specimens, the primary spermatocytes are irregularly divided into non-uniform secondary spermatocytes, however, some specimens perform a regular division. In the majority of triploid flukes, the primary spermatocytes are divided in a regular pattern, but some of the specimens perform an irregular division. The non-uniform spermatids do not perform a spermiogenesis. In the diploid specimens, no spermatozoa were found that were produced by spermiogenesis. Whereas in the triploid specimens, some spermatids distributed uniformly on the surface went through a spermiogenesis. We observed some moving spermatozoa in one triploid specimen. The spermatozoa possibly retain their normal reproductive function.