Polychaos nitidubium (Bovee, 1970)
Diagnosis: large to medium-sized amoeba with an irregular polypodial shape during slow locomotion; palmate form with pseudopodia to be shorter and less numerous than those of P. dubium; uroid morulate, sometimes with villi; crystals squared or bipyramidal; nucleus shallowly to deeply cup-shaped.
Dimensions: Bovee: polytactic form 250-550 µm; monotactic form 250-550 µm; nucleus 27-35 µm. My measurements: polytactic form 230 µm; nucleus 24 µm.
Remarks: I have found only one single specimen in Ankeveen (the Netherlands), in 1975. I am not convinced that this is a well described species. It could fit within the variation of P. dubium, a common species.
In his summary, Bovee (1970) notes: “A new ameba of the ‘proteus’ group, Polychaos nitidubia n. sp., is found in lakes, ponds and streams of the State of Florida, United States of America. It resembles both Polychaos dubia (Schaeffer, 1916) and Amoeba nitida Penard, 1902, in certain respects, but it is distinct from either. It resembles P. dubia in its pseudopodal forms and movements and also in the presence of clumped crystals in the cytoplasm. It resembles A. nitida in the form of the nucleus, which is a cup-shaped disc or an invaginated spheriod. It is smaller than A. nitida, but somewhat larger than P. dubia. Polychaos nitidubia n. sp. is found in habitats similar to those where Amoeba proteus and other species of the ‘proteus group’ occur, and may be present with such species. P. nitidubia n. sp. is 200 to 550 µm long in locomotion; its nucleus is 27 to 35 µm diameter with many submembranellar chromatin granules, but no endosome; cytoplasmic granules are numerous, often in fused groups of 2 to 4 crystals, cytoplasm is clear, viscous; movement is less fluid than that of P. dubia, but resembles it.”
Literature: Bovee, E.C., 1970. The Lobose Amebas: II. A New Ameba of the “Proteus” Group, Polychaos nitidubia N. Sp. Hydrobiologia, 35:3-4