Ciliate protozoa. Coloured scanning electron micrograph (SEM) of ciliate protozoa. The larger single-celled organism is Euplotes 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 blue) in its primitive mouth, known as a buccal cavity. Two smaller ciliates are also present. Magnification: x2000 when printed at 10 centimetre.