The purpose of this page is to present the physical characteristics of amoebas. Amoebas belong to the Subphylum Sarcomastigophora, Superclass Sarcodina. Superclass Sarcodina is divided into two classes: Class Actinopodea and Class Rhizopodea. In the Class Actinopodea, the pseudopodia are slender and have a tendency to radiate out from a central test or shell. Radiolarians and Heliozoans are types of Actipodeans. In the Class Rhizopodea are included many of the well known amoebas. Not all Rhizopods are naked, that is, some of them have siliceous shells. Arcella and Difflugia are common sarcodines of the order Arcellinida (Testacida).  The Foramineferans (Order Foraminiferida) are an ancient group of shelled rhizopods. There are many entozooic amoebas, that is, they live in the gut of many organisms as commensals. Two commom genera are the Entamoeba and the Endamoeba. Endamoeba blatae is found in the gut of cockroaches and related amoebas can be found in termites. Entamoeba hystolitica is the endocommensal of humans. The two orders, Foraminefera and Radiolaria have for untold millions of years contributed to the ocean floor. The shells of these two orders have been sinking to the bottom of the ocean building up a characteristic ooze rich in lime and silica. One of the distinguising characteristics of amoebas is the presence of pseudopods (false feet).  Pseudopodia, used in locomotion and feeding, may be rounded at the tip (lobopodia), pointed (filopodia), branched and fused together (rhizopodia), or somewhat rigid and pointed (axopodia).  Amoebas are normally found under high F/M conditions where large concentration of organic detritus can be found and can tolerate low DO.