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A huge amoeba, possibly the largest of all, sometimes slightly more than 2mm in length!  Multinucleate, some with cysts (most do not).  Feeds on bacteria, fungi, other protists and even multicellular rotifers! (Goodkov et al, 1999). The first isolate now called Chaos illinoisense was named Pelomyxa, (a name now used for a large club shaped anaerobic amoeba) from Illinois (Kudo, 1950, 1951).  This isolate was used in many irradiation experiments (Daniels, 1955; Daniels & Roth, 1958) after which the strain was lost.  Another strain of C. illinoisense has however now been found (Goodkov et al, 1999). At E.M, level some Chaos have a filamentous glycocalyx (C. zoochlorellae, ), whereas others (C. glabrum, C. illinoisense) does not (Smirnov & Goodkov, 1997).  Recent SSUrRNA gene data (Bolivar et al, 2001) confirm the long held suspicion (Page, 1986) that the genus Chaos is closely related to the genus Amoeba.

Chaos at the Protist Information Server     Yuru Deng's work on mitochondrial structure of Chaos  Amoeba

E.M.s Yuru Deng
Described species:-

C. carolinense (700mm - 2mm in length). Monopodal form may be even larger. 

C. glabrum (Smirnov & Goodkov, 1997) (420-980mm in length). From Lake Ladoga, N.W. Russia.  Has a floating form with multiple radiating pseudopods. Two morphotypes of mitochondria observed by EM. The nuclei are biconvex and discoid about 20mm in diameter; 10 on average per cell. Cytoplasm full of bipiramidal crystal and cubic plate-like crystals.  No cysts recorded. 
C. illinoisense (Daniels & Roth, 1964;Kudo, 1950; Goodkov et al, 1999) (500mm - 1.3mm in length)Forms cysts with a double wall. Two morphotypes of mitochondria observed by EM. 
C. nobile (Page, 1986)
C. zoochlorellae (Willumsen, 1982). From a Danish freshwater pond.

Available strains:-

C. carolinense BA-13-1324, from Carolina Biological Supply Co



Bolivar, I., Fahrni, J. F., Smirnov, A. & Pawlowski, J. (2001) SSU rRNA-based phylogenetic position of the genera Amoeba and Chaos (Lobosea, Gymnamoebia): The origin of gymnamoebae revisited.  Mol.Biol.Evol. 18, 2306-2314.

Daniels, E. W. (1955). X-irradiation of the giant amoeba, Pelomyxa illinoisensis.  I. Survival and cell division following exposure. J.Exp.Zool. 130, 183-197.

Daniels, E. W. & Roth, L. E. (1964). Electron microscopy of mitosis in a radiosensitive giant amoeba. J.Cell Biol. 20, 75-84.

Deng, Y., Marko, M., Buttle, K. F., Leith, A., Mieczkowski, M. & Mannella, C. A. (1999) Cubic membrane structure in amoeba (Chaos carolinesis) mitochondria determined by electron microscopy tomography. J.Struct.Biol. 127, 231-239.

Goodkov, A.V., Smirnov, A.V., & Skovorodkin, I.N. (1999). Study of a rediscovered large freshwater multinucleate amoeba Chaos illinoisense (Kudo, 1950). Protistology 1(2), 55-61.

Kudo, R. R. (1950) A species of Pelomyxa from Illinois. Trans.Amer.Micros.Soc. 69, 368-370.

Kudo, R.R. (1951). Observations on Pelomyxa illinoisensisJ.Morphol. 88, 145-173.

Smirnov, A.V. & Goodkov, A.V. (1997). Description of the large mulinucleate lobose amoeba Chaos glabrum sp.n. (Lobosea, Amoebidae), with notes on the diagnosis of the genus ChaosActa Protozoologica 36, 227-233.

Smirnov, A.V. & Goodkov, A.V. (1998). Study of  Polychaos annulatum (Pernard, 1902) comb. nov. with notes on "Polychaos fasciculatum-like" species.  Eur.J.Protozool. 34, 1-9.

Page, F. C. (1986) The genera and possible relationships of the family Amoebidae, with special attention to comparative ultrstructure., Protistologica. 22, 301-316.

Wenstrup, E. J. (1945) Encystment and excystment in Chaos. Science. 101, 407.

Willumsen, N. M. S. (1982) Chaos zoochlorellae nov. sp. (Gymnamoebia, Amoebidae) from Danish freshwater pond. J.Nat.Hist. 16, 803-813.

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