Paramecium bursaria

Paramecium bursaria is a species of ciliate protozoan that has a mutualistic symbiotic relationship with green alga called Zoochlorella. The algae live inside the Paramecium in its cytoplasm and provide it with food, while the Paramecium provides the alga 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 species of Paramecium that forms symbiotic relationships with algae, and are often used in biology classrooms as examples of protozoans, and as examples of symbiosis.