Entamoeba

The entamoebae group of parasitic and commensal amoebae. Entamoebae are uninucleate and small, usually 10-100 μm across, and are typically monopodial with lobose pseudopods taking the form of clear anterior bulges. Cysts are common. This is one of the few groups that lack mitochondria, which is probably a secondary loss associated with their parastic life style; the cells do contain dictyosomes, which are generally supposed to have evolved later. The best known member is Entamoeba histolyca, which is responsible for amoebic dysentery in humans in other mammals. Another well-known species is Entamoeba coli, which is relatively harmless.