[Studies on the fine structure of Toxoplasma gondii tachyzoite]

Toxoplasma gondii tachyzoite was crescent-shaped. The pellicle of the parasite consisted of two membranes. The anterior end contained the polar ring and conoid, the former being the thickened inner membrane and the latter a cylindrical organelle which was made up of about 10 filaments arranged in an oblique row. The subpellicular microtubules numbering 22 originated at the polar ring and extended to the posterior end. The rhoptries extended from the conoid and terminated anterior to the nucleus with a narrow dense neck and an enlarged posterior portion with a glandular structure. The rhoptries perhaps had a secretory function and the conoid might be related to the invasion of the tachyzoite into the host cell.