Stentor polymorphus. Light microscope footage of a green stentor (Stentor polymorphus), a ciliate protozoan. Cilia can be seen lining the peristome, a rim around the oral area. Their rhythmic beating draws bacteria and other organisms into the cytostome or mouth. The green colour is caused by the presence of numerous Zoochlorella algae, with which it has a symbiotic relationship. The algae photosynthesise inside the protozoan, providing it with sugars and oxygen, while deriving protection from their host. Filmed with differential interference contrast illumination.