The Apusozoa are a phylum comprising several genera of flagellate protozoa. They are usually around 5–20 µm in size, and occur in soils and aquatic habitats, where they feed on bacteria. They are grouped together based on the presence of an organic shell or theca under the dorsal surface of the cell.

The Apusozoa are a phylum comprising several genera of flagellate protozoa. They are usually around 5–20 µm in size, and occur in soils and aquatic habitats, where they feed on bacteria. They are grouped together based on the presence of an organic shell or theca under the dorsal surface of the cell.