Trichamoeba sinuosa Siemensma & Page, 1986

Diagnosis: Fast locomotion in a characteristic zigzag pattern. Uroid bulbous, smooth or bearing short villi. Cytoplasm usually contains numerous bipyramidal crystals. Nucleus with small, peripherally arranged nucleoli.

Dimensions: Length 125–325 µm (mean 200 µm). Length‑to‑breadth ratio > 4, usually > 5. Nucleus approximately 14–27 µm (mean 20 µm).

Ecology: Found on aquatic plants and on the bottom of various freshwater habitats. The type material was collected from a polluted canal in Kortenhoef, The Netherlands.

Remarks: Published records are few and geographically limited, and the true distribution of the species remains uncertain. Most observations come from isolated reports, and few have been confirmed with modern methods. At present, T. sinuosa should be regarded as insufficiently documented in terms of its geographical range.

The monopodial form moves in a distinctive zigzag pattern, which inspired the species name sinuosa. Cysts contain two small nuclei and may possess up to three ectocyst layers.

Trichamoeba sinuosa resembles species of Saccamoeba, but can be distinguished by its granular nucleus with peripheral nucleoli. The species is not rare and is easy to culture; in culture, specimens with two nuclei have occasionally been observed.