Examination of nonflagellate and flagellate round forms of Trichomonas vaginalis by transmission electron microscopy.

Plasmodium-like round cells without sections of flagella, round flagellar cells with dividing nucleus and binuclear flagellate round forms were represented from the log-phase of Trichomonas vaginalis cultures. The fine-structural characteristics of the round cells support the opinion that the cells without flagella as well as the round multinuclear flagellate cells represent developmental stages preceding the appearance of mononuclear flagellate cells. In the round cells, amitotic division was observed instead of the well-known cryptopleuromitosis, without formation of metaphasic chromosomes and desmosomes. Our investigations onto the fine structure of the parasite support the assumption that the non-flagellate forms are viable cells of the parasite and point to still unknown phases of its biology.