Paramecium bursaria is a species of ciliates that has a mutualistic endosymbiotic relationship with green algae called Zoochlorella. The algae live inside the Paramecium in its cytoplasm and provide it with food, while the Paramecium provides the algae with movement and protection. P. bursaria is 80-150 μm long, with a wide oral groove, two contractile vacuoles, and a single micronucleus as well as a single macronucleus. P. bursaria is the only spe