Balantidium coli – Trophozoite in formalin-fixed stools

France, Delage Alix

Trophozoite is large (50 µm to 100 µm X 40 µm to 60 µm), oval-shaped, and covered with short cilia. The anterior end is pointed, and has a cytostome. The cytoplasm contains contractile vacuoles, not visible on this pic, and two nuclei. The macronucleus is bean-shaped, and the smaller micronucleus is round.