Portrait of a slightly squashed, Ophryoglena (Ehrenberg,1831), a histophagous hymenostome ciliate some species of which are parasitic. Hosts include the nymphs of dragonflies and mayflies. The life cycle of parasitic forms is polymorphic, this portrait showing what is probably the theront or free-swimming hunter stage. The body is oval to elongate. The somatic ciliature consists of dense longitudinal kineties with a preoral suture. The oral aperture is located in the anterior quarter of the cell and has the outline of a right human ear. The buccal cavity spirals deep into the body and has an undulating membrane and three membranelles. On the left side of the buccal cavity is the refringent organelle of Lieberkühn also referred to as the "watchglass organelle". This can be seen here as a small cup-shaped structure with a collection of pigmented refractile granules adjacent to its convex surface. This structure is thought to play a role in phototaxis which is positive in some phases of the life cycle and negative in others. There are one or two contractile vacuoles each emptying through several pores. The macronucleus is flattened and ellipsoid in outline. From freshwater pond populated by dragonfly and mayfly nymphs near Boise, Idaho. DIC.