Peniculids | ||||||||
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Scientific classification | ||||||||
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Typical families | ||||||||
Suborder Frontoniina     Clathrostomatidae     Frontoniidae     Lembadionidae     Maritujidae     Stokesiidae Suborder Parameciina     Parameciidae     Neobursaridiidae     Urocentridae |
The peniculids are an order of ciliate protozoa, including the well-known Paramecium and its close relatives. Most are relatively large, freshwater forms that feed on smaller organisms swept into the mouth. They have simple life cycles, and in many cases do not even form resting cysts.
Typically the body has uniform, dense cilia, which also cover a vestibule preceding the mouth. Extrusomes are characteristically in the form of spindle trichocysts, which release thread-like shafts, and never mucocysts. The oral cilia include peniculi, corresponding to the membranelles of related groups, arranged parallel to the mouth deep in the oral cavity. Nematodesmata (rods) arise from the bases of the oral or perioral cilia, but these do not support a cyrtos as in some other classes. Two suborders are recognised: