Entamoeba
Entamoeba Casagrandi & Barbagallo, 1895 (ref. ID; 1618)
Synonym Poneramoeba Luhe (ref. ID; 1618)
[ref. ID; 1618]
Nucleus vesicular, with a comparatively small endosome, located in or near the center and with varying number of peripheral nonchromatinic granules attached to the nuclear membrane; chromatin in the endosome and in peri-endosomal region. The genus was established by the two Italian authors who were unaware of the existence of the genus Endamoeba. Numerous species in vertebrates and invertebrates; one species in protozoa; one species free-living. (ref. ID; 1618)
[ref. ID; 4148]
Refer "The biochemistry and Functional Morphology of the Entamoeba". (ref. ID; 4148)
- Entamoeba apis Fantham & Porter (ref. ID; 1618)
- Entamoeba aulastomi Noller (ref. ID; 1618)
- Entamoeba barreti Taliaferro & Holmes, 1924 (ref. ID; 164) reported year? (ref. ID; 1618)
- Entamoeba bovis Liebetanz (ref. ID; 1618)
- Entamoeba buccalis Prowazek
See; Entamoeba gingivalis Gros (ref. ID; 1618)
- Entamoeba butschlii Prowazek, 1912
See; Iodamoeba buetshlii (Prowazek, 1912) Dobell, 1919
- Entamoeba citelli Becker (ref. ID; 1618)
- Entamoeba caprae Fantham (ref. ID; 1618)
- Entamoeba chattoni (ref. ID; 3968)
- Entamoeba cobayae Walker (ref. ID; 1618)
Syn; Entamoeba caviae Chatton (ref. ID; 1618)
- Entamoeba coli (Grassi) (ref. ID; 1618)
Syn; Amoeba coli Grassi, 1879; Endamoeba coli (Grassi, 1879) Hickson, 1908
- Entamoeba cuniculi Brug (ref. ID; 1618)
- Entamoeba debliecki Nieschulz (ref. ID; 1618)
- Entamoeba dispar (ref. ID; 172)
- Entamoeba dysenteriae (ref. ID; 172)
- Entamoeba equi Fantham (ref. ID; 1618)
- Entamoeba gallinarum Tyzzer (ref. ID; 1618)
- Entamoeba gedoelsti Hsiung (ref. ID; 1618)
Syn; Endamoeba intestinalis (Gedoelst) (ref. ID; 1618)
- Entamoeba gingivalis (Gros, 1849) (ref. ID; 1618)
Syn; Amoeba buccalis Steinberg, 1862; Amoeba gingivalis Gros, 1849; Endamoeba gingivalis (Gros, 1849) Smith & Barrett, 1915; Entamoeba buccalis Prowazek, 1904 (ref. ID; 1618)
- Entamoeba histolytica Schaudinn, 1903 (ref. ID; 1618, 3968) reported author and year? (ref. ID; 172, 347, 3681, 3900, 4242)
Syn; Amoeba coli Losch, 1875; Amoeba dysenteriae Councilman & Lafleur, 1891; Endamoeba dysenteriae Kofoid, 1920; Endamoeba histolytica (Schaudium, 1903) Hickson, 1909; Endamoeba dispar Brumpt, 1925; Endamoeba dysenteriae (Councilman & Lafleur, 1891) Craig, 1905; Entamoeba tetragena Hartmann, 1908
- Entamoeba invadens Geiman & Ratcliffe, 1936 (ref. ID; 164)
- Entamoeba invadens Rodhain (ref. ID; 1618)
- Entamoeba minchini Mackinnon (ref. ID; 1618)
- Entamoeba moshkovskii Tshalaia, 1941 (ref. ID; 1307, 1618)
- Entamoeba muris Grassi (ref. ID; 1618)
- Entamoeba nana Wenyon & O'Conner, 1917
See; Endolimax nana (Wenyon & O'Conner, 1917) Burg, 1918
- Entamoeba ovis Swellengrebel (ref. ID; 1618)
- Entamoeba paulista (Carini) (ref. ID; 1618)
Syn; Brumptina paulista Carini (ref. ID; 1618)
- Entamoeba polecki Prowazek (ref. ID; 1618)
- Entamoeba ranarum (Grassi) (ref. ID; 1618)
- Entamoeba terrapinae Sanders & Cleveland, 1930 (ref. ID; 164) reported year? (ref. ID; 1618)
- Entamoeba testudinis Hartmann (ref. ID; 1618)
- Entamoeba thomsoni Lucas (ref. ID; 1618)
- Entamoeba venaticum Darling (ref. ID; 1618)
- Entamoeba williamsi Prowazek, 1911
See; Iodamoeba buetschlii (Prowazek, 1911) Dobell, 1919
Entamoeba apis Fantham & Porter (ref. ID; 1618)
Descriptions
In Apis mellifica; similar to E. coli. (ref. ID; 1618)
Descriptions
In the gut of the horse-leech, Haemopis sanguisuga; cysts with 4 nuclei. (ref. ID; 1618)
Entamoeba barreti Taliaferro & Holmes, 1924 (ref. ID; 164) reported year? (ref. ID; 1618)
Descriptions
In the colon of snapping turtle, Chelydra serpentina. (ref. ID; 1618)
Measurements
Trophozoites 14-23 (18) um long. (ref. ID; 1618)
Descriptions
Uninucleate cysts; in the stomach of cattle and gnu, Connochaetes taurinus. (ref. ID; 1618)
Measurements
5-20 um in diameter; cyst 4-15 um in diameter. (ref. ID; 1618)
Descriptions
In the caecum and colon of the striped ground squirrel, Citellus tridecemlineatus; nucleus 4-6 um in diameter, with a comparatively large endosome which varies in position from central peripheral; cysts with 8 nuclei. (ref. ID; 1618)
Measurements
Rounded trophozoites 10-25 um in diameter; cysts about 15 um in diameter. (ref. ID; 1618)
Descriptions
In goat intestine. (ref. ID; 1618)
Synonym
Entamoeba caviae Chatton (ref. ID; 1618)
Descriptions
Similar to E. coli; in the intestine of guinea-pigs. (ref. ID; 1618)
Synonym
Amoeba coli Grassi, 1879; Endamoeba coli (Grassi, 1879) Hickson, 1908
Descriptions
Cytoplasm not well differentiated; movement sluggish; endoplasm granulated, contains micro-organisms and faecal debris of various sizes in food vacuoles; erythrocytes are not ingested, though in a few cases and in culture, they may be taken in as food particles; nucleus, 5-8 um in diameter, seen in vivo; compared with E. histolytica, the endosome is somewhat large (about 1 um in diameter) and located eccentrically; peripheral granules more conspicuous. The cyst spherical or often ovoid, highly refractile; immature cyst contains 1, 2 or 4 nuclei, one or more large glycogen bodies with distinct outlines, but comparatively small number of acicular, filamentous or irregular chromatoid bodies with sharply pointed extremities; when mature the cyst contains 8 nuclei and a few or no chromatoid bodies. The trophozoites and small number of cysts occur in diarrhoeic or semiformed faeces and the formed faeces contain mostly cysts. (ref. ID; 1618)
Measurements
The trophozoite 15-40 um in diameter; average individuals 20-35 um. Cyst 10-30 um in diameter. (ref. ID; 1618)
Descriptions
Similar to E. coli in both trophic and encysted stages; in the intestine of rabbits. (ref. ID; 1618)
Descriptions
Cysts uninucleate; in the intestine of pigs and goats. (ref. ID; 1618)
Measurements
5-10 um in diameter. (ref. ID; 1618)
Descriptions
Nucleus oval; cysts tetranucleate; seen in the faeces of horse. (ref. ID; 1618)
Measurements
40-50 by 23-29 um; cyst 15-24 um in diameter. (ref. ID; 1618)
Descriptions
In the caeca of chicken, turkeys and possibly other fowls. (ref. ID; 1618)
Measurements
Trophozoites 9-25 (16-18) um. Cysts octonucleate 15 by 12 um. (ref. ID; 1618)
Synonym
Endamoeba intestinalis (Gedoelst) (ref. ID; 1618)
Descriptions
In the colon and caecum of horse; endosome eccentric; bacteria-feeder. (ref. ID; 1618)
Measurements
6-13 by 6-11 um. (ref. ID; 1618)
Synonym
Amoeba buccalis Steinberg, 1862; Amoeba gingivalis Gros, 1849; Endamoeba gingivalis (Gros, 1849) Smith & Barrett, 1915; Entamoeba buccalis Prowazek, 1904 (ref. ID; 1618)
Descriptions
This amoeba lives in carious teeth, in tartar and debris accumulated around the root of teeth, and in abscesses of gums, tonsils, etc. The trophozoite is as active as that of E. histolytica; cytoplasm well differentiated; monopodal progressive movement in some individuals; endoplasm hyaline, but vacuolated, and contains ordinarily a large number of pale greenish bodies (which are probably nuclei of leucocytes, pus cells or other degenerating host cells) and bacteria in food vacuoles; nucleus, 2-4 um in diameter, appears as a ring; when stained it shows a small central endosome and small peripheral granules closely attached to the membrane. Encysted forms have not been observed in this amoeba.
E. gingivalis is the very first parasitic amoeba that has become known to man. Gros (1849) found it in Russia in the tartar on the surface of the teeth. Some observers maintain that this amoeba is the cause of pyorrhoea alveolaris, but evidence for such an assumption seems to be still lacking. It has found in the healthy gums and even in false teeth. Therefore, it is generally considered as a commensal. It is widely distributed and of common occurrence. (ref. ID; 1618)
Measurements
Trophozoite 8-30 um (average 10-20 um) in diameter. (ref. ID; 1618)
Entamoeba histolytica Schaudinn, 1903 (ref. ID; 1618, 3968) reported author and year? (ref. ID; 172, 347, 3681, 3900, 4242)
Synonym
Amoeba coli Losch, 1875; Amoeba dysenteriae Councilman & Lafleur, 1891; Endamoeba dysenteriae Kofoid, 1920; Endamoeba histolytica (Schaudium, 1903) Hickson, 1909; Endamoeba dispar Brumpt, 1925; Endamoeba dysenteriae (Councilman & Lafleur, 1891) Craig, 1905; Entamoeba tetragena Hartmann, 1908
Descriptions
[ref. ID; 347]
- Light microscopy: Surface modifications of living trophozoites of E. histolytica strains HM1:IMSS and HK9, cultured under axenic conditions, included lobopodia situated at the advancing edge or the lateral regions of the amebas, endocytic cups or stomas scattered over the free cell surface, and, less frequently a posterior tail or uroid. These transient specializations of the cell surface were more evident in early monoxenic cultures. Translational movement and displacement of intracellular vesicles were more rapid in monoxenic cultures compared to axenic amebas. Filopodia were only exceptionally observed in living cultures using both Nomarski and phase contrast optics, even under high magnification. When visible, filopodia were short and usually associated with the uroid. Cell division was frequently found in all cultures. Although the process of separation of daughter amebas was initially rapid, incompletely divided cells were usually linked by a thin cytoplasmic bridge for several minutes. Lobopodia and endocytic stomas rapidly appeared and disappeared while the uroid was more stable. No significant differences were observed between living amebas attached to plastic coverslips and those attached to the luminal surface of cultured epithelial MDCK cells even when time-lapse microcinematography was employed (unpublished observations). (ref. ID; 347)
- Electron microscopy: Trophozoites of E. histolytica attached to plastic coverslips or to the upper surface of MDCK cell monolayers were polymorphic. This variation in shape and surface morphology was such that, in any particular field, a given ameba always appeared different from its neighbors. The free surface of trophozoites had an appearance that ranged from smooth to wrinkled. The latter frequently showed minute openings approximately 0.1-0.2 um in diameter, corresponding to the openings of micropinocytic vesicles. The surface was generally smooth on lobopodia and over round cytoplasmic protrusions measuring 4-8 um located on the free surface of the trophozoites. The number of endocytotic stomas varied from 1-12 in a single trophozoite. Their external diameter ranged from 3-14 um, and the internal diameter from 0.6-10 um. When visible, the external opening of the endocytic channel was usually single, but occasionally, an endocytic stoma gave rise to several opening. Endocytotic stomas or food cups displayed a wide range of diameters; smaller ones had uniform cytoplasmic borders, while the larger structures had wrinkled lips with irregular contours. Filopodia were usually limited to the peripheral rim of the basal surface of trophozoites in contact with either plastic or cultured epitherlial cells. Only rarely were filopodia found to originate from the free surface that faced the culture medium. Two broad categories of filopodia were observed: the more numerous were 0.2 um or less in diameter and could not be visualized with light microscopy while the others were thick, more than 0.5 um in diameter and were usually found at the uroid. In general, the thin and thick filopodia were only a few micrometers in length, but a few were more than 30 um long. In some instances, a single and very long filopodium that represented the remainder of the cytoplasmic bridge present at the end of cell division was found. The HM1:IMSS strain under both axenic and monoxenic conditions could be clearly differentiated from the HK9 strain since the former had very few short filopodia of the thin type. Even at the uroid region, amebas displayed numerous thick and thin filopodia, which were particularly abundant at the uroid, a flattened region located at the posterior end of the parasite that also contained a large number of small blebs. The basal surface of trophozoites detached either from plastic or epithelial monolayers was unremarkable in both strains. When present, filopodia were exclusively limited to the outer rim of the basal region of attachment and were absent from the surface in contact with the substrate. Openings of micropinocytic vesicles were frequently observed while openings of endocytic stomas were only rarely found on the basal surface of detached trophozoites. The only morphological difference in the basal regions of amebas attached to plastic and natural substrates was the smooth appearance of the former. No other surface specializations that could be related either to the adhesive or the cytopathic properties of the protozoan were found at the basal region of detached trophozoites. The surface morphology of HM1:IMSS amebas cultured in association with bacteria was much more pleomorphic than that of the axenic amebas. Large endocytic stomas, 12 um or more in diameter, were particularly prominent. Short, thick filopodia were commonly observed in monoxenic cultures. (ref. ID; 347)
[ref. ID; 1618]
The trophozoite is an active amoeba: Cytoplasm usually well differentiated; eruptive formation of large lobopodia, composed largely of ectoplasm; when fresh, active monopodal progressive movement; the vesicular nucleus appears in life as a ring, difficult to recognize; food vacuoles contain erythrocytes, tissue cell fragments, leucocytes, etc.; stained nucleus shows a membrane, comparatively small peripheral granules, a centrally located small endosome and an indistinct network with a few scattered chromatin granules. The trophozoite multiplies by binary fission. The amoeba lives in the lumen and in the tissues of the wall of the colon, and brings about characteristic ulceration of the colon which is typically accompanied by symptoms of amoebic dysentery. Through the portal vein, the amoeba may invade the liver in which it produces abscess, and other organs such as lung, brain, testis, etc. The infection in these organs is referred to as amoebiasis. Under certain circumstances not well understood, the amoebae remain small after division. Such amoebae are sluggish and known as the precystic forms. The precystic amoeba secretes presently a resistant wall and becomes encysted. The highly refractile cyst is spherical. At first it contains a single nucleus which divides twice. The mature cyst contains 4 nuclei. In addition the cyst contains diffused glycogen and elongated refractile rod-like bodies with rounded extremities which stain deeply with haematoxylin. These inclusions are absorbed and disappear as the cyst matures. No further changes take place in the cyst as long as it remains outside the host's intestine. The trophozoites are found in dysenteric or diarrhoeic faeces, but formed faeces usually contain cysts. The cyst is the stage by which the organism begins its life in a new host. The life-cycle of Entamoeba histolytica in human host is unknown. The amoeba has, however, been cultivated in vitro by numerous investigators since the first successful cultivation by Boeck & Drbohlav (1925). Entamoeba histolytica, is commonly known as the "the dysentery amoeba", was first definitely recognized by Losch in Russia in 1875. It is now known to be widely distributed in tropical, subtropical and temperate regions alike, although it is more prevalent in warmer regions. The serious of water-borne infection in crowded areas is easily realized when one recalls the outbreak (some 1400 cases) of amoebic dysentery and amoebiasis which originated in Chicago in 1933, where defective plumbing in certain establishments contaminated the water system with the cysts of Entamoeba histritica and the development of some 100 cases of amoebic dysentery among firemen who drank contaminated water in connection with the 1934 fire of the Union Stockyards in Chicago. Another example is the outbreak of amoebiasis among the employees of a plant as the water was contaminated with cysts. (ref. ID; 1618)
[ref. ID; 3900]
- Light microscopy: Filopodial extensions were frequently seen on living trophozoites of E. histolytica examined by phase-contrast microscopy. In some progressively motile forms, the trailing ends of the trophozoites were pulled out to extreme length (>100 um) by attachment of filopodia to the substrate or to other cells. More commonly, numerous short (several um) filopodia were seen in a restricted area at the posterior surface of actively motile forms. Rounded trophozoites often had a tuft of multiple filopodia arising from a small surface area. More commonly, filopodia could be seen randomly distributed on any part of the cell surface. The length of filopodia and the number/cell were variable. Many of the shorter filopodia were inflated at the tip. Occasionally, vesicles formed at the tips and could be seen as they moved down filopodia, finally disappearing at the cell surface. (ref. ID; 3900)
- HVEM and SEM: HVEM has proved useful in the study of the interior of whole mammalian tissue culture cells. We learned, however, that the cytoplasmic structure of intact critical point dried E. histolytica trophozoites could not be visualized by this technic, as the amebae were to thick to be penetrated by the 1000 kV electrons. It was possible, however, to see that the periphery of whole trophozoites had irregular bulges, vesiculations, and surface filopodia. These fixed filopodia ranged in length from several to over 30 um. Some were branched and some had fusiform swellings at various points. When seen in the scanning electron microscope, the surface of E. histolytica trophozoites was undulating, finely wrinkled and covered at irregular intervals by protruding vesicles or blebs of various sizes. Lobopodia and filopodia were the most prominent structures on the trophozoite surface. Some filopodia were quite long. In trophozoites which appeared to have been fixed while progressively motile, the largest numbers of filopodia were associated with the uroid area. The uroid was a thin, fan-shaped shelf of cytoplasm from which about 60 filopodia arose. The majority of these filopodia were adherent to the Formvar substrate and appeared to be drawn out behind the advancing ameba. The cell was examined by HVEM before the finder grid was mounted on the SEM stub. Its filopodia were ~0.1 um in diameter and bounded by a unit membrane with a glycocalyx (0.025 um deep) indistinguishable from that of the cell surface. Many of these filopodia terminated in knobs. The cytoplasm of filopodia was devoid of organelles and had the mesh-like trabecular appearance described as typical of critical point dried cytoplasm in intact mammalian cells. Some trophozoites, fixed while apparently at rest, had no distinct tail or uroid region, but possessed a tuft of many filopodia. In these cases, the filopodia in the tufts arose from a restricted area of the surface, ~5 um2, and were not attached to the substrate. Other filopodia, not associated with either the uroid or tufts, were branched and had fusiform inflations at their tips or along their length. Some of these filopodia protruded singly from the upper surface of trophozoites; others were grouped along the lower surface near the point of contact with the substrate. The base of the latter type was bilaterally flattened and bifurcated at a point ~2/3 of the way from the trophozoites surface to the tip. Many of these bifurcated and branched filopodia were inflated at their tips. (ref. ID; 3900)
Measurements
The trophozoite 7-35 (9-20) um in diameter; cyst 5-20 um in diameter. (ref. ID; 1618)
Descriptions
Resembles E. histolytica; active locomotion; feed on leucocytes, liver cells, epithelial cell debris, bacteria, etc.; nucleus similar to that of E. histolytica. Cysts with one to four nuclei; glycogen vacuole; chromatoid bodies acicular, rod-like or cylindrical. Host include various reptiles. (ref. ID; 1618)
Measurements
Trophozoites 15.9 um in average diameter (9.2-38.6 by 9-30 um); cysts 13.9 (11-20) um in diameter. (ref. ID; 1618)
Descriptions
In gut of tipulid larvae; cyst nuclei up to ten in number. (ref. ID; 1618)
Measurements
5-30 um in diameter. (ref. ID; 1618)
Descriptions
This amoeba resembles E. histolytica, but appears to be free-living in the sewage. The organism is actively motile and assumes limacid form during locomotion. The nucleus resembles closely that of E. histolytica. No contractile vacuole occurs. Cysts are spherical, when mature it contain 4 nuclei, glycogen vacuoles and chromatoid bodies. (ref. ID; 1618)
Measurements
9-29 um or more, but commonly 11-13 um in largest diameter; cysts 7-17 um in diameter. (ref. ID; 1618)
Descriptions
In the caecum of rats and mice; cytoplasm with rod-shaped or fusiform bacteria and flagellates coinhabiting the host's organ; nucleus 3-9 um in diameter and resembles closely that of E. coli; cysts with 8 nuclei when mature. (ref. ID; 1618)
Measurements
Trophozoite 8-30 um; cysts 9-20 um in diameter. (ref. ID; 1618)
Entamoeba ovis Swellengrebel (ref. ID; 1618)
Descriptions
Cyst uninucleate; in the intestine of sheep. (ref. ID; 1618)
Synonym
Brumptina paulista Carini (ref. ID; 1618)
Descriptions
In the cytoplasm of many species of opalinids; cysts uninucleate. (ref. ID; 1618)
Measurements
Trophozoites 5.3-14.3 um in diameter; cysts about 9.4 um in diameter. (ref. ID; 1618)
Descriptions
In colon of pigs; cyst uninucleate. (ref. ID; 1618)
Measurements
10-12 um in diameter; cyst 5-11 um in diameter. (ref. ID; 1618)
Descriptions
In colon of various species of frogs; resembles E. histolytica; cysts are usually tetranucleate, but some contain as many as 16 nuclei; amoebic abscess of the liver was reported in one frog. (ref. ID; 1618)
Measurements
10-50 um in diameter. (ref. ID; 1618)
Entamoeba terrapinae Sanders & Cleveland, 1930 (ref. ID; 164) reported year? (ref. ID; 1618)
Descriptions
Cysts tetranucleate when mature; upon excystment, the cyst content divides into 4 uninucleate amoebulae; in the colon of Chrysemys elegans. (ref. ID; 1618)
Measurements
Trophozoites 10-15 um long; cysts 8-14 um in diameter. (ref. ID; 1618)
Descriptions
In intestine of turtles, Testudo graeca, T. argentina, T. calcarata and Terrapene carolina. (ref. ID; 1618)
Descriptions
In the colon of cockroaches; usually attached to debris by a knob-like process, highly adhesive; cytoplasm poorly differentiated; vesicular nucleus with peripheral granules; endosome variable, with loosely aggregated granules and a central dot; cyst with one to four nuclei. (ref. ID; 1618)
Measurements
Rounded form 7-30 (15-25) um in diameter; cysts 8-16 um in diameter. (ref. ID; 1618)
Descriptions
In the colon of dog; similar to E. histolytica; since the dog is experimentally infected with the latter, this amoeba discovered from spontaneous amoebic dysentery cases of dogs, in one of which were noted abscesses of liver, is probably E. histolytica. (ref. ID; 1618)