Poterioochromonas cells are encountered as small sessile or free-swimming naked trophic cells, or as silica-walled cysts ("stomatocysts" or "statospores") found in sediments.

The uninucleate trophic cells are spherical to elongate and approximately 5-15 Ám long. The external form of the cell is very plastic. The two flagella are subapically inserted. The anterior flagellum is much the longer, and is usually directed forward. The posterior flagellum is very short and points more or less to the cell posterior.

The plastid varies in shape and size, depending on the mode of nutrition being used by the cell at the time of observation. The plastid contains no pyrenoid and no eyespot.

Sessile cells rest on a thin long-stalked lorica that is very difficult to see under the light microscope.

The cyst is a spherical thickwalled structure with a protruding aperture at the apex.

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