Epistylis is a single-cell ciliate with a non-contractile stalk that grows in branching colonies. In this freshwater sample, an Epistylis colony had attached to a Copepod (microscopic crustacean).

Higher magnification reveals an inverted-bell shaped protozoan with a single ring of cilia around its prominent peristomal lip.

Epistylis coloonies in home aquariums can spread on fish, leading to bacterial infection and a quick death.