Ultrastructure of spermatogonia and spermatocyte lobules in Taenia solium strobilae (Cestoda, Cyclophyllidea, Taeniidae) from golden hamsters

Abstract

Golden hamsters (Mesocricetus auratus) were infected with Taenia solium metacestodes dissected from infected pig meat. Adult worms were collected from hamster intestines of animals killed 5–60 days post-infection (dpi), incubated in RPMI 1640 medium with or without colchicine, fixed and processed for transmission electron microscopy (TEM). Sections for light microscopy from 40 different blocks with scolex, immature and mature proglottids were photographed. Thin sections were cut from 25 selected blocks, examined and photographed with TEM. Metaphase mitosis figures were observed in the subtegument of the germinative tissue and interpreted as germ cell precursors. In immature proglottids (20 dpi), discrete cell clusters of three to four cells surrounded by a thin cytoplasmic envelope were identified along the inner border of the lateral excretory ducts. These were also observed in more mature proglottids (40–60 dpi) as clusters of eight cells enclosed in a cytoplasmic envelope, with nuclei of spermatogonia exhibiting the synaptolems of primary meiotic cells. In mature proglottids from 45 dpi, a large number of spermatocyte lobules were found, exhibiting different stages of spermatogenesis from primary spermatocytes to mature filiform spermatids with a single axoneme, annular nucleus and spiral cortical microtubules, similar to spermatozoa described for type III spermiogenesis of species of the family Taeniidae. All mature spermatocyte lobules were enclosed in a highly organized cellular envelope and surrounded by a basal lamina. The envelopes contained a number of distinct organelles, seen in cross-section as discrete lattices of microtubules located between two layers of plasma membrane, as well as thickened furled cytoplasm with numerous strands of rough endoplasmic reticulum and pockets of microtubules.