Polychaos fasciculatum (Penard, 1902)
Diagnosis: Polypodial, palmate amoeba with short, parallel pseudopodia and large fasciculate uroid, especially at the beginning of locomotion. Length in locomotion 65-140 µm (average 110 µm), monopodial, clavate locomotive forms may appear under low oxygen tension (Page, 1988). Crystals are truncate bi-pyramids. Floating form of radial type; several thick pseudopodia of unequal length radiate from irregular central mass of the granuloplasm. Single spherical nucleus, 11-23 µm in diameter, with nucleolar material in few narrow peripheral lobes, usually crescent shaped, sometimes in a single curved band, twisting inside the nucleus.
Ecology: Freshwater, Europe, South-America (I found it in sediment of Lake Argentina, 2017).
Remarks: Surface coat consists of very fine filaments, often collapsing under inappropriate fixation. This species may be confused with Polychaos annulatum, however the latter has very distinct nuclear structure. Careful examination of 3D organization of the nucleolus always excludes any doubts about the species identification. Comparison of Polychaos fasciculatum-like amoebae was done by Smirnov & Goodkov (1998).
