Colpidium ciliate protozoan. Coloured scanning electron micrograph (SEM) of the protozoan Colpidium. This single-celled organism is ciliate, being covered in hair-like structures known as cilia. It lives in freshwater environments. It feeds on bacteria and decaying organic matter, which it filters through membranelles in its primitive mouth, known as a buccal cavity (lower left). The membranelles, rows of fused cilia (short microscopic hairs), are also used for locomotion (lower left). Magnification: x1300 when printed at 10cm wide