Photos: A. Goodkov, A.Smirnov
Crystals (1), cysts(2-3) and nuclei(4-7).
Photos: A. Goodkov
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
Note that the keys by Page from 1988 and 1991 gives dimensions
of this speices, but does not contain illustrations.
- 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
- "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
- 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.
Special thanks to A.V. Goodkov and I.I. Skovorodkin for data and
illustrations on this species.
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