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Dennis Kunkel's Microscopic World 2001 Calendar

Protozoa are single-celled organisms that live primarily in aquatic environments. The genus Vorticella is a stationary protozoan that attaches by a stalk to substrates such as plants or rocks. Here the main cell area has a ring of cilia (which is shown in yellow) near a mouth-like opening. The cilia are short, whip-like threads that, in this case, beat the water to create a current that brings smaller unicellular organisms into Vorticella's digestive area. (Some species of motile protozoa move about in water by beating their cilia.) Protozoa are important microscopic components of aquatic food chains. In 1675, Vorticella was one of the first creatures observed and described by the pioneer Dutch microscopist Leeuwenhoek.