Light microscope differential interference contrast (DIC) footage of ciliate protozoa feeding on bacteria on the surface of toad spawn. The green spheres are Chlamydomonas algae. The small brown protozoa are Coleps sp. Ciliate protozoa are tiny single-celled organisms found in water. They feed on bacteria and decaying organic matter, which they filter through membranelles in their primitive mouth, known as a buccal cavity. The membranelles, rows of fused cilia (short microscopic hairs), are also used for locomotion.