TOXOCARA-CANIS (NEMATODA, ASCARIDIDAE) - ULTRASTRUCTURE OF THE RACHISAND THE OVARIAN WALL

The oogonia and oocytes in the ovaries of Toxocara canis are joined to a cytoplasmic process called the rachis. The rachis is a muchbranched cytoplasmic mass without cell components in the germinal zone. At the end of the germinal zone and in the growth zone the cytoplasmic mass is formed into a central axial cylinder, containing small dense granul es, lipid drops and glycogen. Throughout the growth zone shell granule s similar to those present in the oocytes are also present in the rach is. Anterior to the opening of the ovaries into the oviduct the rachis disappears. The ovarian wall is composed of epithelial cells, adjoini ng the basal lamina. They are characterized by the presence of large n umbers of mitochondria, especially in the germinal zone. The epithelia l cells in the growth zone also contain rough endoplasmic reticulum, r ibosomes and bundles of microfibrils. A dense tubular material occurs between the basal membrane of the epithelial cells and the basal lamin a as well as in the wall intercellular spaces in the ovarian growth zo ne. Multivesicular labyrinth-like formations can also be observed in t he epithelial intercellular spaces in the central portion of the T can is ovary.