Flamella arnhemensis Kudryavtsev et al., 2009
Diagnosis: Locomotive form fan-shaped, with irregular anterior margin and numerous long trailing filaments; numerous long narrow subpseudopodia sometimes present. Spherical or ovoid vesicular nucleus, with a central nucleolus; large motile cells with up to 15–20 nuclei may be present in cultures. About 10 asynchronously working contractile vacuoles in the granuloplasm.
Cysts uninucleate 10.3–18 µm in diameter (average 13.3 µm); cyst wall 480–500 nm thick, consists of threelayers: inner most layer continuous, 40–60 nm thick; granular medium layer with ostioles and operculae (1.8–2.9 mm in diameter), 240–290 nm thick; fibrillar outer layer 190–290 nm thick, sometimes with a separated outer sheet (corresponding to ectocyst visible with LM) 110–140 nm thick.
Dimensions: length 13–34 µm (average 20 µm), breadth 23–69 µm (average 41 µm), l-b ratio 0.29–0.8 (average 0.49). Nucleus 3–8 µm (average 5.2 µm), nucleolus 1.5–4 µm (average 2.7 mm); my measurements: length 14–35 µm, breadth 38–58 µm; nucleus c. 4.5 µm, nucleolus c. 2.9 µm. They agree very well with the measurements made by Kudryavtsev et al.
Ecology: freshwater, aerobic, the Netherlands, Arnhem. I found this species in the Laegieskamp, also in the Netherlands.