Description of Tetrahymena pyriformis

A species complex of hymenostome ciliates, 25-90 micrometres long. Body ovoid, narrowing anteriorly. Mouth pear-shaped, or approximately triangular, in the anterior quarter, parallel to longitudinal axis of the cell; with undulating membrane on the right and three small membranelles on the left. Uniformly ciliated, in longitudinal rows; with straight preoral suture. One spherical macronucleus, central; one contractile vacuole, subterminal. Bacterivore; in fresh water.