Trichamoeba Fromental, 1874 (ref. ID; 4238), Fromental, 1874 emend. Schaeffer, 1926 (ref. ID; 3687) or Fromental, 1874 emend. Siemensma & Page, 1986 (ref. ID; 7606)

Family Amoebidae Ehrenberg, 1838 (ref. ID; 7606, 7615)

[ref. ID; 4238]
This genus was created by Fromentel to include two species, T. hirta and T. radiata. An amoeba similar to T. hirta was, however, described by Wallich (1863) under the name of Amoeba villosa, and that author is credited with the type species, Trichamoeba villosa Wallich, 1863. Schaeffer (1926) reviewed the taxonomic status of this genus, refined it, and described six new species. Two other species were described by Bovee (1972). Although Page (1976) recognized four species, T. villosa, T. myakka Bovee, 1972, T. osseosaccus Schaeffer, 1926, and T. cloaca Bovee, 1972, he later disputed the similarity between T. hirta and A. villosa and rejected the synonymy (F.J. Siemensma & F.C. Page, unpbl.). The genus Trichamoeba is characterized by the presence of, during locomotion, a uroid consisting of numerous, thin, hair-like projections extending from the posterior end and by an elongate clavate body shape, with the anterior part wider than the posterior. No pseudopods other than sub-hemispherical projections are formed. Branching pseudopods are never formed. Movement is rapid and effected usually by eruptive waves. No rayed stage is known to occur. Bovee included Trichamoeba in the family Pelomyxidae Schulze, 1877, in the sub-order Limacina Bovee & Jahn, 1966, along with two other limax amoebae, Pelomyxa and Saccamoeba. Page, however, has included Trichamoeba in the family Amoebidae with other polypodial amoebae such as Amoeba Bory de St. Vincent, 1822, Chaos Linnaeus, 1767, and Polychaos Schaeffer, 1926, instead of the family Hartmannellidae Volkonsky, 1931, along with other typically limax amoebae. Presence of both polypodial and a clavate limax form was reported for the type species, T. villosa by Bhowmick (1966). Bovee (1951) found that the pseudopodia of T. osseosaccus exceeded hemispherical dimensions and he recommended that the generic characteristics of Trichamoeba be revised. The amoeba described here is frequently polypodal with a palmate form although a tubular limax form with villous-bulb uroid has been observed in some trophozoites. Ultrastructural features are becoming increasingly important in the taxonomy of amoebae, cell surface structures being significant criteria. In the Amoebidae, surface structures can vary from filaments as in some species of Amoeba, Chaos, and Polychaos, to an amorphous layer as in A. leningradensis and a Trichamoeba sp. The amorphous layer on the cells surface of T. mycophaga supports its inclusion in the Amoebidae genus Trichamoeba rather than the Hartmannellidae genus Saccamoeba. In the latter, the cell surface coating is very thin and in well fixed specimens bears delicate hexagonal cup-shaped structures similar to those in other Hartmannellidae. Another important characteristic of Amoebidae is the presence of an inner fibrous lamina in the nuclei of many genera. The honeycomb laminae of A. proteus reported by Page & Kalinina (1984) also occur in A. leningradensis (1984) and P. dubium (1974). Amoeba algonquinensis (1983) lacks complex honeycomb organization; instead, layers of parallel fibers occur between the nucelolar bodies and the nuclear membrane. The presence of these fibers in the nuclei of A. algonquinensis has been confirmed by F.C. Page (pers. commun.). Although nuclei in most genera of Amoebidae contain several nucleoli or granular nucleolar bodies, P. fasciculatumm as well as T. mycophaga has a single nucleus with only one nucleolus. Within the genes Trichamoeba, T. myakka and T. cloaca have granular chromatin as does a new species from Holland. On the other hand, four of 10 species included by Schaeffer (1926) within Trichamoeba and including the types species. T. villosa (1966), have a single mass of centrally located nucleolar material. Similar diversity in nucleolar organization has been noted in the genus Thecamoeba. (ref. ID; 4238)

[ref. ID; 7606]
Re-diagnosis; Uninucleate. Regularly monopodial in locomotion, advancing by steady flow or non-eruptive antero-lateral bulging. All or most cytoplasmic crystals bipyramidal. Surface coat of filamentous material, more or less amorphous in arrangement. No discernible inner lamina in nucleus of the one species studied electron-microscopically. Free-living. (ref. ID; 7606)
Remarks; The genus Trichamoeba was established by Fromental (1874) for two species, T. hirta and T. radiata, without designation of a type species. He defined the genus by two characters: -Nous avons cree ce genre pour des Amibes peu diffluentes, mais avec des changements assez profonds dans la forme du corps. Le tegument est orne de cils raides et non vibratiles-. Schaeffer (1926) in re-defining the genus, narrowed it to amoebae with a monopodial form and a uroid of numerous villi. However, he created two problems. First, his generic definition has now proved to be inadequate because it was too broad. It includes not only Amoebidae (as defined by Page 1976) but also amoebae now recognised as members of the genera Rhizamoeba (Page 1972) and Saccamoeba (Bovee 1972; Page 1974). Schaeffer did not make any distinction between uni- and multinucleate species and even suggested that the parasitic Endamoeba barreti probably belonged to this genus. The necessity of defining this heterogenous group more clearly was noticed by Bovee (1951) and Page (1974). The genus Saccamoeba was re-defined and separated from Trichamoeba by Bovee (1972), mainly on the basis that the former has a vesicular nucleus. Unfortunately, Bovee did not give a generic diagnosis of Trichamoeba independent of the definition of his proposed new subfamily, the Trichamoebinae, members of which, according to this diagnosis, have granular nuclei. That subfamily is not used here, and a redefinition of Trichamoeba is now necessary. The genus Rhizamoeba was separated from Trichamoeba by Page (1972) on the basis of differences in uroidal structures. The second problem concerns 'the type species of Trichamoeba (Page 1972). Schaeffer (1926) rejected one of Fromental's original species, T. radiata, from the genus because it was probably a Nuclearia. He considered Fromentel's other species, T. hirta and T. lieberkuehnia Maggi, 1880, as synonyms of Wallich's (1863) Amoeba villosa, and on this ground he designated A. villosa as the type species of Trichamoeba. (ref. ID; 7606)
Notes; Schaeffer's (1926) designation of the type species is valid insofar as he chose T. hirta, one of Fromental's (1874) original species, but invalid in its attempted synonymisation of T. hirta with Amoeba villosa Wallich, 1863, resulting in Schaeffer's use of 'Trichamoeba villosa' as the name of the types species. According to the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature, 1985), Amoeba villosa cannot be made the type species if it is not a synonym of one of the two species which Fromentel included (article 69). Since we do not accept that synonymy, we conclude, according to our interpretation of Article 69 and of Schaeffer's proposal, that Schaeffer (1926) was really designating T. hirta as the type species. As one reason for rejecting the supposed synonymy, the length of T. hirta was, according to he magnification of Fromentel's figure, approximately 125 um, while the A. villosa of Wallich (1863) was up to 500 um long. Furthermore, the description of A. villosa and additional information spread out over the three papers cited indicate that Wallich's amoeba undoubtedly was polypodial. Fromentel's amoeba was not polypodial, and Schaeffer's statement that the genus Trichamoeba had 'No pseudopods other than sub-hemispherical projections' makes clear his intention to include only monopodial amoebae. (ref. ID; 7606)
Type species; Trichamoeba hirta Fromental, 1874 (ref. ID; 7606)

[ref. ID; 7615]
Uninucleate. Regularly monopodial in locomotion. All or most cytoplasmic crystals bipyramidal. Surface coat of fuzzy appearance and nucleus without discernible inner lamina in the one species examined electron microscopically. Free-living. (ref. ID; 7615)
Type species; Trichamoeba hirta Fromental, 1874 (ref. ID; 7615)

  1. Trichamoeba caerulea (ref. ID; 2618)
  2. Trichamoeba clava Schaeffer, 1926 (ref. ID; 3687) reported year? (ref. ID; 3491)
  3. Trichamoeba cloaca Bovee, 1972 (ref. ID; 4238)
  4. Trichamoeba coerulea Schaeffer, 1926 (ref. ID; 3687)
  5. Trichamoeba frenzeli Lepsi, 1960 (ref. ID; 3687 original paper)
  6. Trichamoeba gumia Schaeffer, 1926 (ref. ID; 2618, 3687)
  7. Trichamoeba hirta Fromental, 1874 (ref. ID; 7606, 7615) reported author and year? (ref. ID; 2618)
  8. Trichamoeba monofila Lepsi, 1960 (ref. ID; 3687 original paper)
  9. Trichamoeba myakka Bovee, 1972 (ref. ID; 4238)
  10. Trichamoeba mycophaga Chakraborty & Old, 1986 (ref. ID; 4238 original paper)
  11. Trichamoeba osseosaccus Schaeffer, 1926 (ref. ID; 3687, 4238, 7606) reported author and year? (ref. ID; 2618)
  12. Trichamoeba pallida Schaeffer, 1926 (ref. ID; 2618, 3687)
  13. Trichamoeba pavonia Lepsi, 1960 (ref. ID; 3687 original paper)
  14. Trichamoeba radiata (ref. ID; 2618)
  15. Trichamoeba schaefferi Radir, 1927 (ref. ID; 2618, 3687)
  16. Trichamoeba sinuosa Siemensma & Page, 1986 (ref. ID; 7606 original paper)
  17. Trichamoeba sphaerarum Schaeffer, 1926 (ref. ID; 3687) reported author and year? (ref. ID; 2618)
  18. Trichamoeba urotricha (Lepsi, 1953) (ref. ID; 3687)
  19. Trichamoeba villosa (Wallich, 1863) (ref. ID; 2618, 3687)

Trichamoeba mycophaga Chakraborty & Old, 1986 (ref. ID; 4238 original paper)


Trophozoites palmate to elongate, predominantly polypodial but may be monopodial in continuous locomotion, appearing tubular or clavate with a villous-bulb uroid. Ectoplasmic cap on pseudopodia and at advancing margin of limax trophozoites. Endoplasm highly granular with elongated and bipyramidal crystals up to 2.5 um long. Usually a single contractile vacuole, 3-15 um in diameter, located in the posterior portion of the cell. Trophozoites uninucleate with spherical to oval nuclei, 4-10 um in diameter. Nucleolar material organized in a single unfragmented structure, oval to elongate, 2.8-5.0 um in diameter. Trophozoite dimensions: 45-136 um long and 25-94 um wide. Cysts rounded to oval, 21-60 um in diameter, ecto- and endocyst walls separated by amorphous material several um in thickness. (ref. ID; 4238)



Trichamoeba mycophaga has been shown to feed on spores of several fungi including Cochliobolus sativus, Cylindrocarpon didymum (Hartig) Wollenw., Fusarium oxysporum fsp. pini (Hartig) Snyd. & Hansen, Epicoccum nigrum Link ex Link, and Endothia gyrosa (Schw. Fr.) Fries. Along with some other mycophagous amoebae and myxobacteria, this amoeba is among the very few organisms capable of lysing melanized fungal propagules in soil. It is thought to be a facultative fungal feeder also using bacteria as food organisms. (ref. ID; 4238)

Type material

Held by the authors. An active culture has been deposited with the Culture Centre for Algae and Protozoa, Institute of Terrestrial Ecology. (ref. ID; 4238)

Trichamoeba osseosaccus Schaeffer, 1926 (ref. ID; 3687, 4238, 7606) reported author and year? (ref. ID; 2618)


T. osseosaccus looks similar to T. sinuosa, but there are differences. During locomotion the amoeba is irregularly clavate to oval in outline, with a more flattened form. This form has never been observed in T. sinuosa. Bovee (1951) describes an obligate clavate form with the width of the posterior end half to two-thirds that of the anterior end, while T. sinuosa is more cylindrical with the width of the anterior part differing not strongly from those of the posterior end. The trailing filaments of T. osseosaccus are produced by adhesion of ectoplasm to the substratum; both Schaeffer and Bovee (1951) describe this collopodium-like appearance and Schaeffer's drawing of the uroid leaves no doubt upon the adhesive nature of the filaments. The uroid of T. sinuosa never shows this structure and the villi are never formed by adhesion. The nucleolar material of T. osseosaccus is arranged in a single layer immediately beneath the nuclear membrane, while the nucleus of T. sinuosa shows a distinct clear space between the layer of nucleolar material and the nucleolar membrane. A floating form with long pseudopodia as observed by Bovee, has never been observed in T. sinuosa. (ref. ID; 7606)

Trichamoeba sinuosa Siemensma & Page, 1986 (ref. ID; 7606 original paper)


Locomotive form normally slightly sinuous, with length approximately 200 um. Nucleus spherical, diameter 14.4 to 26.9 um (mean approximately 20 um), with a peripheral layer of granular nucleolar material. Crystals always present, mostly truncate bipyramids. Uroid smooth or papillate or covered with villi. Glycocalyx approximately 20-25 nm thick above plasma membrane. No discernible inner nuclear lamina. Presumed cysts binucleate; endocyst approximately 53 um in diameter. (ref. ID; 7606)



The sinuous form gave the amoeba its specific name. (ref. ID; 7606)

Known habitat

Fresh water, the Netherlands and Denmark. (ref. ID; 7606)

Type locality

T. sinuosa was isolated in the autumn of 1981 from a small, shallow canal ('s-Gravelandse Vaart, Kortenhoef), in the central part of the Netherlands. (ref. ID; 7606)

Type slides

T. sinuosa have been deposited in the British Museum (Natural History) and assigned the following numbers: holotype, 1985:12:3:1; paratype, 1985:12:3:2. (ref. ID; 7606)


Amoebae from natural sources varied in length between 125 um and 204 um (average 173 um), with a length:breadth ratio of 4.1-6.5 (average 5.3) (n= 0). Cultured amoebae were larger, from 180 um to 324 um (average 222 um), with a length:breadth ratio of 5.2-12.5 (average 7.6) (n=30). (ref. ID; 7606)