Euplotes ciliate protozoan. Coloured scanning electron micrograph (SEM) of a ciliate protozoan (Euplotes sp.). This single-celled organism is found in fresh and marine water. It is covered in cilia (microscopic hairs) that are used for locomotion and to waft food towards its mouth. It feeds on bacteria and decaying organic matter, which it filters through membranelles (rows of fused cilia) in its primitive mouth, known as a buccal cavity (slit at bottom left).