Testate amoeba. 400x magnification. Brightfield microscopy.

Usually when we think of amoebas we think of amorphous single cells creeping around microscope slides. This is still the case for testate aboebae, however the shapeshifting amoeboid cell lives inside a protective shell-like covering called a test. The test is made of chitin, a polysaccharide (a multi-unit sugar molecule) that is also found the exoskeletons of crabs and other arthropods, the beaks of squids, and the cell walls of fungi. The cell interacts with the world from within this test through a hole in the top through which the pseudopodia (cellular projections full of cytoplasm that the organism extends and withdraws to create motion and engulf food) can emerge and move the organism around.