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 macronucleus appears as a beaded chain. 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.