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Chaos illinoisense,
Locomotive forms.
Photos: A. Goodkov, A.Smirnov

Chaos illinoisense,
Crystals (1), cysts(2-3) and nuclei(4-7).
Photos: A. Goodkov

Chaos illinoisense,
Cell coat (1-2,8), food vaculoe (3),
mitochondria of different types (4-6)
and bacteria in the cytoplasm (7).
Photos: A. Goodkov

Chaos illinoisense (Kudo, 1950) Goodkov, Smirnov & Skovorodkin, 1999
  • Amoebae are orthotactic or polytactic in locomotion. Polytactic specimens have few anteriorly directed pseudopodia. Lentgh in locomotion from 650 mkm in polytactic forms to 1300 mkm in orthotactic amoebae. Uroid bulbous or morulate, presents mostly in actively moving orthotactic specimens. Crystals are truncate bipiramids and platelike rectangles. Floating form of radial type, non-symmetrical, resembles that of A. proteus.

  • "Several hundred"(Page, 1988) of spherical, granular nuclei, 14-16 mkm in diameter.

  • Cyst-forming, cysts spherical, double-walled, with two separated walls. The average diameter of the ectocyst 250 mkm.

  • The cell coat is 48 nm in thickness and consists of two layers. The basal layer is amorphous, about 9 nm in thickness, the distal one about 39 nm in thickness and appeares to be filamentous. However, discrete filaments are not distinguishable (Goodkov et al., 1999).

  • Mitochondrial heteromorphism has been noted (op.cit.)

  • This species may resemble Chaos glabrum and Chaos nobile in the appearance of the locomotive form, however it is much larger than both of them. The number of nuclei differs it well from both mentioned species. It can be confused with Chaos carolinense, the distinctive features are the shape of nuclei (biconvex discs in Chaos carolinense and spheres in Chaos illinoisense) and the structure of the cell coat (distinct filaments is a characteristic of Chaos carolinense). TEM of the cell coat is preferble to confirm identification, keep in mind that filaments in proteus-like amoebae may coagulate under the EM fixation.

  • The culture is maintained in the Laboratory of the Cytology of Unicellular Organisms, Institute of Cytology RAS, Tichoretskij Prospect 4, St.Petersburg, Russia.
  • Freshwater, Central North America, North-Western Russia.
    Cultivation: PJ+ Colpidium colpoda or Tetrachymena spp. May be maintained for some time in PJ + wheat (rise) grain, in presence of small ciliates and flagellates.

  • Basic references for identification

  • Goodkov A.V., Smirnov A.V. and Skovorodkin I.N. 1999. Study of a rediscovered large freshwater multinucleate amoeba Chaos illinoisense (Kudo, 1950).Protistology 1(2):55-61.
  • Kudo R.R. 1951. Observations on Pelomyxa illinoisensis J. Morphol. 88: 145-173.
  • 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.
Note that the keys by Page from 1988 and 1991 gives dimensions of this speices, but does not contain illustrations.

Special thanks to A.V. Goodkov and I.I. Skovorodkin for data and illustrations on this species.

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