The species Carchesium on an activated sludge particle
of the sewage plant of Oldenburg. The cells without appendix
are about 50 ┬Ám in length.
Members of genus Vorticella represent one of the most impressive group within the Protozoa. They occur in nature as single organisms as well as in colonies looking like a bunch of flowers. They are ubiquitary in freshwater and seawater habitats where their favorite food, bacteria, occur in high concentrations. The micrograph shows an activated sludge sample of a sewage plant. Vorticella has cleared the water from small free-living bacteria while filamentous bacteria are too big to be get sucked in.

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