- Intestinal Species : ( Entamoeba histolytic, Entamoeba hartmanni ,Entamoeba coli, Entamoeba polecki ,Endolimax nana , Iodamoeba bütschlii)

Extra-intestinal Species
Entamoeba gingivalis ,Acanthamoeba species ,Naegleria fowleri
Countries that have poor sanitary conditions. In the United States, amebiasis is often found in immigrants from and people who have traveled to underdeveloped countries. Furthermore ameobas may be present and thus infect individuals in areas and institutions in which crowded conditions prevail It is important to note that only one of the intestinal ameobas, E. histolytica, may produce characteristic symptoms, and is universally considered to be a pathogen. Infections with each of the extraintestinal amebas may cause symptoms that are other than intestinal in nature, often involving such areas as the mouth, eye, and brain.

Entamoeba histolytica
Common associated disease or condition names Intestinal ameobiasis, amebic colitis, amebic dysentery , extraintestinal ameobiasis.
Morphology
Trophozoites. The trophozoites (trophs) of E. histolytica range in size from 8 to 65 ?m, with an average size of 12 to 25 ?m (Figs. 3-2 to 3-4 Table 3-1). Note that parasite names are often shortened to just the first letter of the genus followed by the species name; E. histolytica is the abbreviated version of Entamoeba histolytica.
The trophozoite exhibits rapid, unidirectional progressive movement, achieved with the help of finger-like hyaline pseudopods. The single nucleus typically contains a small central mass of chromatin known as a karyosome (also referred to as karyosomal chromatin).
Variants of the karyosome include eccentric or fragmented karyosomal material. The karyosome of this amebic parasite is surrounded by chromatin material, a morphologic structure called peripheral chromatin This peripheral chromatin is typically fine and evenly distributed around the nucleus in a perfect circle. Variations, such as uneven peripheral chromatin, may also be seen.
Although the karyosome and peripheral chromatin appearance may vary, most trophozoites maintain the more typical features described. The invisible nucleus in unstained preparations becomes apparent when stained. Stained preparations may reveal lightly staining fibrils located between the karyosome and peripheral chromatin. The E. histolytica trophozoite contains a finely granular cytoplasm, which is often referred to as having a ground glass in appearance. Red blood cells (RBCs) in the cytoplasm are considered diagnostic because E. histolytica is the only intestinal ameba to exhibit this characteristic. Bacteria yeast, and other debris may also reside in the cytoplasm, but their presence, however, is not diagnostic.