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Polychaos dubium Institute of Cytology RAS
Locomotive forms, nucleus, crystals. DIC.
Scale bar 20 mkm. Photo: A.Smirnov, A.Goodkov

Polychaos dubium Institute of Cytology RAS

1: nucleus, 2: nuclear lamina, 3: dyctyosomes,
4: mitochondria, 5: cell coat. Scale bar is 500nm.
TEM: A.Smirnov, A.Goodkov from the preparations
by D. Gromov, Inst. of Cytology RAS.

Polychaos dubium (Schaeffer 1916)

  • Polypodial, "palmate" amoeba with short, parallel pseudopodia and large fasciculate uroid (especially at the beginning of locomotion). Pseudopodia tend to fuse at their bases as the main cell mass advances. Normally, pseudopodia move toward the posterior end, narrowing and giving rise to the fascicle of pseudopodial remnants, thus forming a fasciculate uroid. Length of amoebae in locomotion 280-400 mkm (average 310 mkm). Single nucleus of granular type, ovoid or spherical, 35-45 mkm (mean 38 mkm) in diameter. Crystals are bipyramids or plate-like rectangles. There are "paired bodies", and irregular-shaped crystal-like inclusions in the cytoplasm.

  • Cysts were reported, but this observation must be confirmed.

    Floating form of radial type; several thick pseudopodia of unequal lenght radiate from irregular central mass of the granuloplasm.

  • Surface coat consists of very fine filaments 170-180 nm in length, radiating from the plasma membrane. Filaments are extremely fine and often collups under unappropriate fixation. This species has fibrous honeycomb-like inner nuclear lamina, 250-320 nm in thickness. Mitochondrial heteromorphism" has been noted

  • This species may be confused with smallest specimens of Amoeba proteus or species of the genus Deuteramoeba, however the latter have very disting nuclear structure. TEM of the cell coat is obligate for identification of this species.

  • Culture is maintained at the Laboratory of Cytology of Unicellular Organisms, Institute of Cytology RAS.

  • Freshwater, Known from North America, England, Netherlands, Sweden, Western Russia. Cultivation: PJ medium + Tetrahymena and other accompanying small protists. Can be maintained for some time in PJ + wheat (rise) grain, in presence of Tetrahymena only.
  • Basic references for identification:
    • Flickinger C.J. 1974. The fine structure of four "species" of Amoeba. J. Protozool. 21. 59-68.
    • Page F.C. 1986. The genera and possible relationships of the family Amoebidae, with special attention to comparative ultrastructure. Protistologica. 22: 301-316.
    • Page F.C. 1988. A new key to freshwater and soil gymnamoebae. FBA, Ambleside. 122p.
    • Page F.C. 1991. Nackte Rhizopoda. in: Protozoenfauna, b.2. Gustav Fisher, Stuttgart. 3-172.
    • Schaeffer A.A. 1916. Notes on the specific and other characters of Amoeba proteus Pallas (Leidy), A. discoides spec. nov., and A. dubia spec. nov. Arch. Protistenk. 37. 204-228.
    • Schaeffer A.A. 1926. Taxonomy of the Amebas. Papers Dept. mar. Biol. Carnegie Inst. Wash. 24. 3-112.

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