Stentor polymorphus. Light microscope footage of several of green stentor (Stentor polymorphus) attached to plant material. This species of freshwater ciliate protozoan feeds mainly on bacteria, using its hair-like cilia to waft food particles into its oral area. Its green colour is caused by the presence of numerous individual Zoochlorella sp. 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 darkfield illumination.