Light microscope phase contrast illuminated footage of ciliate protozoa feeding on bacteria on the surface of toad spawn. The green spheres are Chlamydomonas algae. 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.