Trichamoeba

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)

Trichamoeba caerulea (ref. ID; 2618)
Trichamoeba clava Schaeffer, 1926 (ref. ID; 3687) reported year? (ref. ID; 3491)
Trichamoeba cloaca Bovee, 1972 (ref. ID; 4238)
Trichamoeba coerulea Schaeffer, 1926 (ref. ID; 3687)
Trichamoeba frenzeli Lepsi, 1960 (ref. ID; 3687 original paper)
Trichamoeba gumia Schaeffer, 1926 (ref. ID; 2618, 3687)
Trichamoeba hirta Fromental, 1874 (ref. ID; 7606, 7615) reported author and year? (ref. ID; 2618)
Trichamoeba monofila Lepsi, 1960 (ref. ID; 3687 original paper)
Trichamoeba myakka Bovee, 1972 (ref. ID; 4238)
Trichamoeba mycophaga Chakraborty & Old, 1986 (ref. ID; 4238 original paper)
Trichamoeba osseosaccus Schaeffer, 1926 (ref. ID; 3687, 4238, 7606) reported author and year? (ref. ID; 2618)
Trichamoeba pallida Schaeffer, 1926 (ref. ID; 2618, 3687)
Trichamoeba pavonia Lepsi, 1960 (ref. ID; 3687 original paper)
Trichamoeba radiata (ref. ID; 2618)
Trichamoeba schaefferi Radir, 1927 (ref. ID; 2618, 3687)
Trichamoeba sinuosa Siemensma & Page, 1986 (ref. ID; 7606 original paper)
Trichamoeba sphaerarum Schaeffer, 1926 (ref. ID; 3687) reported author and year? (ref. ID; 2618)
Trichamoeba urotricha (Lepsi, 1953) (ref. ID; 3687)
Trichamoeba villosa (Wallich, 1863) (ref. ID; 2618, 3687)

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

Diagnosis

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)

Descriptions

Trophozoite: Amoebae in locomotion often appear palmate to elongate in shape. A slender tubular shape typical of the so-called "limax" form also frequently occurs. Trophozoites measure 45-136 um in length and 25-94 um in width. A distinctive floating form has not been observed. Suspended cells in aqueous cultures may appear quite extended and branched although at other times, irregularly rounded amoebae with short, radially projecting, tubular pseudopodia may be seen in disturbed cultures. Trophozoites do not readily adhere to glass or plastic although in still cultures the posterior of many trophozoites may flatten and be attached to the bottom of the dish and generally spread in all directions. One to many pseudopodia of the "lobosa" type may be formed simultaneously advancing in the same or in different directions. In a newly formed pseudopodium, a hyaline crescent is present; however, the hyaline ectoplasmic cap may not be visible in rapidly moving trophozoites as the granular endoplasm soon follows the hyaline ectoplasm. Several pseudopodia are generally extended by an advancing trophozoite and the number of pseudopodia changes constantly by repeated subdivision and reunification. Only one of these becomes the major pseudopodium and determines the direction of movement, but other pseudopodia may form concurrently and take over this role at any time. Under continuous locomotion, trophozoites may have an elongate, broadly monopodial or clavate form, usually with a hemispherical posterior bulb (uroid) bearing, a fringe of short filaments. The uroid appears to be ectoplasmic and is often connected to the main body of the limax trophozoite by a narrow isthmus. In active cultures, rate of locomotion is approximately 2 um sec-1. The cell cytoplasm consists of a clear ectoplasmic zone and a dense highly granular endoplasm containing phase bright crystals. These are either elongated, less than one um long, or bipyramidal and 1-2.5 um long. The number and proportion of each type of crystal varies in different trophozoites. A posteriorly located contractile vacuole, 3-15 um in diameter, and the nucleus are the other cytological details distinguishable by light microscopical examination. All the 100 or so trophozoites examined so far were uninucleate. Nuclei are spherical to oval, measuring 4-10 um in diameter, and contain a single, spherical, or oval nucleolus 2.8-5.0 um in diameter. (ref. ID; 4238)
Ultrastructure: The cell is bounded by a plasma membrane approximately 10 nm thick covered with an electron-dense amorphous material extending up to 100 nm into the suspending medium. The cytoplasm is markedly divided into ectoplasm quite devoid of organelles and endoplasm crowded with organelles. The ectoplasm is broadest anteriorly, forming a hyaline cap. Other regions of the cell membrane which are thrown into complex invaginations may correspond to the uroid. Organelles include numerous small vesicles, some containing food particles, bacteria, and fungal spores in various stage of lysis. No crystalline structures as seen by light microscopy have been found. These may have dissolved during fixation procedures. Page & Baldock (1980) showed remains of similar crystals in Polychaos fasciculatum. Bacteria are present freely in the cytoplasm, suggesting a symbiotic relationship with the amoeba. Mitochondria are typically rod-shaped or ellipsoidal in profile with vesicular cristae. Golgi bodies are common and dictyosomal in morphology, occurring singly or paired. Endoplasmic reticulum is preset throughout the endoplasm. Other structures present are granules, approximately 30-50 nm in diameter. These are apparently the products of fungal cell breakdown. Lipid bodies are common, especially in amoebae fed on Fusarium macroconidia which contain large lipid reserves, and microfibrils are sometimes seen. The latter vary in occurrence in different sectioned trophozoites and are commonly aggregated into cluster similar to those shown by Bhowmick (1966) for Trichamoeba villosa. The nuclear membrane varies in morphology, sometimes appearing relatively entire and at other times having a beaded appearance due to a large number of pores being present. The nucleoplasm is most dense immediately within the membrane, with a diffuse region extending to the single spherical nucleolus traversed by very fine threads of electron-dense material. Aggregations of filaments arranged in bundles of up to five fibers have been found to be distributed radially through the peripheral, more dense nucleoplasm. The function of these structure is not known. No cysts were observed in sectioned preparations of amoebae. (ref. ID; 4238)
Cyst morphology: In cultures older than three weeks maintained at 25 degrees C, a proportion of trophozoites stop active locomotion, withdraw pseudopodia, and contrast in size. The ectoplasmic layer gradually disappears and the amoeba appears as a dense irregular mass of refringent granules and crystals, measuring 17-35 um in diameter. While many of these cells may be moribund, it seems likely that a proportion gives rise to cysts. Cysts are spherical, elongated or oval, measuring 21-60 um in diameter, and may form either singly or in groups. The cyst wall is distinctly divided into an ectocyst and an endocyst separated by a yellowish amorphous layer, several micrometers thick. Excystment has not be observed. (ref. ID; 4238)

Ecology

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)

Remarks

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)

Diagnosis

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)

Descriptions

Light microscopy:
- 1. General shape and behaviour. The locomotive form was an unbranched cylinder, usually with a sinuous form, with the anterior end slightly broader than the posterior. No dorsal ridges were observed. There were two manners of locomotion. The first was a rapid advance by steady flow. The speed was approximately 340 um per minute at room temperature; the highest observed speed was 480 um per minute. The second kind of locomotion was slightly slower. The amoeba moved by a succession of non-eruptive bulges, alternately to the right and the left side of the anterior end, giving the amoeba a sigmoid or sinuous form as it constantly re-directed its anterior end. Such an antero-lateral bulging was the beginning of a new monopodium. The former anterior end remained as a bulge along the side of the amoebae until it reached and was absorbed into the posterior end. These remnants of former anterior ends could thus be seen as slight curves along the monopodium. Each remnant could potentially produce a new pseudopodium, eventually leading to a new monopodium. Formation of a lateral pseudopodium always coincided with a decrease in locomotive speed and commonly led to a new direction of movoment. Short pseudopodia, nearly hemispherical, usually numbering two or three, appeared when the amoeba slowed down and ceased its advance. Such pseudopodia were formed at apparently random points on the cell. Eventually one pseudopodium lengthened and grew out into a new monopodia. A new direction could also taken by reversal of the anterior-posterior polarity. Such a reversal could happen within a few seconds. During steady flow the amoeba changed direction by moving its anterior end slightly to one side, resulting in an arched path. During continuing locomotion a hyaline cap was not present, as it was constantly penetrated and filled up by granuloplasm. A hyaline cap occurred at the formation of a new pseudopodium but disappeared when the monopodium lengthened. When a hyaline cap was being formed, the hyaloplasm never ran back along one side of the cell mass (Page 1972). The floating form was an irregular sphere with unequal pseudopodia projecting in several directions, and filled or partly filled with granuloplasm. This floating form was very different from that of Saccamoeba, which is just a rather irregular sphere, often with little bumps but never with distinct pseudopodia. (ref. ID; 7606)
- 2. Nucleus. Normally each cell contained one spherical nucleus, though occasionally binucleate indiviuals could be observed. The presumed nucleolar material was arranged in small pieces forming a regular layer beneath the nuclear membrane. Between this peripheral layer of granular material and the nuclear membrane a distinct, narrow, clear space was always visible. A central homogenous body was observed in vivo with differential interference contrast microscopy and also, but very obscurely, in bright field. In stained preparations this body was very prominent. Both borax carmine and iron haematoxylin showed the cental structure clearly. This body is clearly no endosome as no trace of an endosome was found in any e.m. section. It seems to be an optical effect in vivo and an artefact in stained preparations. The diameter of the nucleus in cultured amoebae ranged from 16.8 um to 26.9 um (average 22.3 um), while the diameter of the nucleus in amoebae field sample was smaller, 14.4-22.8 um (average 16.4 um). Nuclei were measured in 30 amoebae from each source. (ref. ID; 7606)
- 3. Uroid. The uroid was not pronounced. It seldom had a knob-like appearance. Its common form was that of a clear, digitiform pronounciation, sometimes forming a sharp or slight angle with the main cell mass. The outline of the uroid could change from moment to moment. The uroid could be smooth, papillate or covered with fine villi. A smooth uroid was more common than a villous one, and an adhesion uroid was never observed. (ref. ID; 7606)
- 4. Crystals. Usually many bipyramidal crystals were present, varying in size from 2.1 to 10.8 um (normally 2.4-5.2 um). Large crystals showed clearly distinguishable forms with truncate ends; small crystals often had an obscure form. All crystals were positioned eccentrically in small vacuoles, though the vacuoles were often discerned only with difficulty. The diameter of such a vacuole was approximately twice that of the crystal which it contained. Amoebae in field samples tended to contain fewer crystals than cultured amoebae. (ref. ID; 7606)
- 5. Vacuoles. Optically empty vacuoles were often numerous in the cytoplasm. The contractile vacuole was often situated towards the posterior end, between the nucleus and the uroid. Often it was very pronounced, forming a hemispherical bulge on the outline of the cell mass. It was often formed by coalescence of several small vacuoles. (ref. ID; 7606)
- 6. Cyst-like bodies. Formation of cyst-like bodies was observed only in the first month after establishment of the culture, and the number in each culture dish declined sharply during that period. Since then, such bodies were never again formed. The term 'cyst-like body' rather than 'cyst' is employed because excystment of a cell was never seen. In each culture dish 10-20 amoebae had rounded up and were firmly adherent to the substrate. One to three layers formed around the granular cell mass. The inner layers was separated from the protoplasm by a clear space. The central body or endocyst measured 50.4-75.6 um in diameter (mean approximately 53 um). Each presumed cyst contained two nuclei, normally close together. The diameters of the nuclei franged from 12.0 um to 16.8 um. The nucleolar material formed a compact, nearly homogeneous layer, immediately beneath the nuclear membrane. The cytoplasm in the cyst-like bodies was highly granular. (ref. ID; 7606)
- 7. Food. Ingested food in the cultures consisted of small ciliates (Chilomonas sp., Halteria sp.), a small rotifer, and bacteria. (ref. ID; 7606)
Electron microscopy: The cell surface usually had the rather amorphous, fuzzy appearance. However, favourable sections suggested a loose but distinct structure within the glycocalyx, perhaps consisting of delicate cylindrical elements, possibly hexagonal in cross section, with a maximum diameter of 25 or 30 nm. The best sections did not yield more detail, and these elements were not distinctly formed or discrete enough to be considered glycostyles. The overall thickness of the glycocalyx was 20-25 nm above the plasm membrane. The fine structure of the nucleus was strikingly like that of Hydramoeba hydroxena (Page and Robson 1983): the highly irregular outline, the lack of any discernible inner fibrous lamina, the parietal arrangement of the nuclear material in many fragments, and the complete absence of a central nucleolus or karyosome. The nucleolar pieces were somewhat smaller and more numerous in T. sinuosa than in H. hydroxena, according with the impression gained from light microscopic observations. Sausage-shaped mitochondria (i.e., elongate with parallel sides) were fairly common, though numerous elliptical and oval profiles were also seen. The tubular cristae occasionally branched. The Golgi system took the form of numerous dictyosomes, often with several in a single section. Such a body usually consisted of five or six flattened cisternae with associated vesicles, with an overall breadth up to 0.85 um. The rough endoplasmic reticulum consisted of somewhat flattened vesicles or short cisternae, never long tracts as in some other Amoebidae. A distinct cortical filamentous layer marked the boundary between the granuloplasm, containing all but the smallest cytoplasmic inclusions, and the hyaloplasm. The outer region of the uroid consisted entirely of hyaloplasm, and an aggregation of cytoplasmic filaments was present in the vicinity of the neck-like constriction between the uroid and the main cell mass. None of the vesicles could be identified unquestionably as containing the crystals observed with the light microscope. (ref. ID; 7606)

Etymology

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)

Measurements

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)