








Moderators: rjlittlefield, ChrisR, Chris S., Pau
Medium- to large-sized ciliate, oval to pyriform in outline,
transparent. The oral aperture is situated in the anterior quarter of the body,
and is characteristically the shape of the concha of the right human ear with a
small posterior projection similar to the tragus of the ear. The buccal cavity
contains an undulating membrane and three membranelles which are
arranged helically. On the left of the oral aperture there is a refringent body,
shaped like a watch glass, often with a pigment spot on its convex side. The
spot is green-yellow in life and stains deeply with iron haematoxylin and
safranin and its location is used as a character for the identification of the
species. The somatic ciliation is dense with many kineties running longitudinally
down the body (except in one species where they spiral, Canella and
Rocchi-Canella, 1976). There is a definite pre-oral suture. One or two
contractile vacuoles open laterally to the right of the oral aperture. The
macronucleus is circular or elliptical in outline, strongly flattened and more
or less folded on itself. Careful observation is required not to attribute a
sausage or horseshoe shape to the nucleus of this genus.