Polychaos

Polychaos Schaeffer, 1926 (ref. ID; 649, 3687, 4238, 7615)

Family Amoebidae Ehrenberg, 1838 (ref. ID; 7615)

[ref. ID; 649]
When Schaeffer (1926) created the genus Polychaos for the species which he had described (Schaeffer 1916) as Amoeba dubia, he included Amoeba fasciculata in that genus, apparently without having seen the organism himself. Lepsi (1960) appears to have been the first author to correct the names to Polychaos dubium and P. fasciculatum, but he did not see the latter species. Polychaos Schaeffer, 1926 was characterised by Page (1976) in a diagnosis somewhat abridged but not differing essentially from that of Schaeffer (1926) as follows: "Usually polypodial, with several tubular pseudopodia, more or less equal and with no one dominant, proceeding anteriorly and antero-laterally from common posterior mass; pseudopodia sometimes flattening and broadening towards ends; may be monopodial in rapid locomotion; no dorsal, ridges; nucleus granular or with other arrangements of nucleolar material reported." In the genus Page included P. dubium, the type-species, and P. fasciculatum, P. nitidubium Bovee 1970, P. timidum Bovee 1972. (ref. ID; 649)

[ref. ID; 7615]
Uninucleate. Commonly polypodial, with pseudopodia often orginating more or less separately from main cell mass; often a posterior group of trailing pseudopodial remnants. Cytoplasmic crystals often distinct bipyramids. Cell coat of many fine, more or less straight filaments radiating from plasma membrane or of some such filaments and shorter, crinkled filaments. Inner nuclear lamina with honeycomb-like structure or fibrous material parallel to nuclear membrane. (ref. ID; 7615)
Type species; Polychas dubium (Schaeffer, 1916) (ref. ID; 7615)

  1. Polychaos (Amoeba) dubium (Schaeffer, 1916) (ref. ID; 7615), (Schaeffer, 1917) (ref. ID; 3687) reported author and year? (ref. ID; 4728, 4817, 4836, 4837)
    Syn; Amoeba dubia Schaeffer, 1916 (ref. ID; 1335)
  2. Polychaos fasciculatum (Penard, 1902) (ref. ID; 3687), (Penard, 1902) Schaeffer, 1926 (ref. ID; 649) or Schaeffer, 1926 (ref. ID; 7554)
    Syn; Amoeba fasciculata Penard, 1902 (ref. ID; 649, 7554)
  3. Polychaos nitidubium Bovee, 1970 (ref. ID; 649)
  4. Polychaos timidum Bovee, 1972 (ref. ID; 649)

Polychaos (Amoeba) dubium (Schaeffer, 1916) (ref. ID; 7615), (Schaeffer, 1917) (ref. ID; 3687) reported author and year? (ref. ID; 4728, 4817, 4836, 4837)

Synonym

Amoeba dubia Schaeffer, 1916 (ref. ID; 1335)

Description

Numerous pseudopodia flattened and with smooth surface; crystals, few large up to 30 um long and of various forms among which at least four types are said to be distinct; contractile vacuole one or more; fresh water. (ref. ID; 1618)

Measurements

About 400 um long. (ref. ID; 1618)

Polychaos fasciculatum (Penard, 1902) (ref. ID; 3687), (Penard, 1902) Schaeffer, 1926 (ref. ID; 649) or Schaeffer, 1926 (ref. ID; 7554)

Synonym

Amoeba fasciculata Penard, 1902 (ref. ID; 649, 7554)

Re-diagnosis

Advancing mass varying between single, broad pseudopodium and up to five subcylindrical pseudopodia, with frequent production of new pseudopodia and lateral fusion of bases; temporary hyaline caps on pseudopodia; posterior end of amoeba narrowed, often with finely morulate or villous uroid and often trailing several digitiform pseudopodial remnants; length in locomotion approximately 65 to 180 um, with mean about 108 to 113 um; only monopodial forms reaching greatest length. Nucleus approximately 11 to 23 um in diameter; nucleolar material parietal, discernible as a single, elongate, curved body or two or more lobes, more or less homogeneous in texture to light microscope. Significant electron-microscopical characters: filamentous surface coat generally extending to 80 nm above plasma membrane with some filaments 280 nm long; nuclear envelope lacking definite internal fibrous lamella. (ref. ID; 649)

Descriptions

Active cells of P. fasciculatum are about 140 um in length and the characteristic locomotive form is palmate (Penard 1902) although there is considerable variation, some specimens being virtually monopodial. The nucleus is diagnostic with two crescentic marginal nucleoli which give it a bowl shaped appearance, while the cytoplasm contains numerous bipyramidal refractile granules. (ref. ID; 7554)

Comments

Amoeba fasciculata was described by Penard (1902) from a marsh and a pond in Switzerland. All subsequent descriptions appear to be based on Penard's, as was that of Page (1976). With no further collections of the species reported. Penard's organism had a mean size of 140 um, produced several subcylindrical pseudopodia, and often had several finger-like uroidal appendages, which were the source of the specific epithet. Its nucleus had a parental nucleolus described as consisting of two crescents on opposite sides of the nucleus, rather than the many small nucleolar bodies occurring in the well-known species of Amoebidae. (ref. ID; 649)

Habitat

Fresh water; reported from Switzerland, England, the Netherlands. (ref. ID; 649)

Locality

From two chalk streams (the River Ffrome at East Stoke and the Tadnoll Brook) in Dorset, England. These were relatively unpolluted (Class 1, Department of the Environment, 1978), well oxygenated, highly calcareous streams (Ca++ 85 mg/l). (ref. ID; 7554)

Polychaos nitidubium Bovee, 1970 (ref. ID; 649)

Descriptions

This species is another large amoeba, up to 550 um, with many nucleoli and posterior projections resembling the pseudopodial remnants of P. fasiculatum and P. dubium. (ref. ID; 649)

Polychaos timidum Bovee, 1972 (ref. ID; 649)

Descriptions

This species is a smaller amoeba with a nuclear structure unlike that of its congeners and with more pointed projections. (ref. ID; 649)