This taxon contains many free-living species and some are moderately pathogenic protozoan parasites of humans and other animals.

Life Cycle

These are typically or extracellular, direct life cycle parasites of the intestinal tract, and transmit via ingestion of cysts in contaminated water.


Its members typically possess four flagella for locomotion. There is just a single type of nucleus. In some species this arrangement is doubled, resulting in eight flagella and two nuclei.