Tetrahymena rostrata was first described by Kahl as Paraglaucoma rostrata and later assigned to Tetrahymena by Corliss. The identification of Tetrahymena rostrata in field samples is difficult given the life cycle of this ciliate. It is facultatively parasitic in slugs (e.g. Deroceras reticulatum) or grazes on dead rotifers and insect larvae (s. fig. 4 a-b). During life cycle, Tetrahymena rostrata passes through different developmental stages and assumes different body shapes (slender-oval and transparent to pear-shaped and opaque) depending on its nutritional state. In addition to this variability, Tetrahymena rostrata is also easily confused with Glaucoma maupasi. However, the latter species has no caudal cilium and the contractile vacuole on the left side.

Tetrahymena rostrata is best identified by the transverse striation of the pellicle (s. fig. 1e), the caudal cilium and the mouth opening in the anterior fifth with an undulating membrane on the right side (s. fig. 3b).