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Paramecium bursaria is a species of ciliate protozoan that has a mutualistic symbiotic 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 species of Paramecium that forms symbiotic relationships with algae, and it is often used in biology classrooms both as an example of a protozoan and also as an example of symbiosis. Shown magnified 400X using a combination of darkfield and phase contrast lighting.
