Zoochlorella

Plural  Zoochlorellae,   any small green alga (often Chlorella) or, sometimes, flagellate protozoan (e.g., the chlamydomonad Carteria) that lives within the bodies of various freshwater protozoans and invertebrates. Zoochlorellae often colour their hosts green (e.g., green hydra and green Paramecium bursaria). As symbionts, zoochlorellae use carbon dioxide and nitrogenous and phosphorous