Shelled amoeba. Light microscope footage of an Arcella sp. testate (shelled) amoeba. The circular shell is formed from the polysaccharide chitin. The shell has a hole in its centre from where finger-like pseudopods emerge, as seen here. This amoeba is found in freshwater ponds and puddles. It can develop vacuoles of carbon dioxide in its body to float up to the water's surface. Filmed with differential interference contrast illumination.