Phylum Ciliophora.

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paramecium close upThe Phylum Ciliophora("Ciliates") consists of a wide array of Protists characterized by the presence of Cilia over at least some of their cell surface during at least part of their life cycle. Cilia are are similar to flagella except they are generally much shorter than the length of the cell. Cilia, like flagella may be used for locomotion in which case their action is similar to the arms of a swimmer in that there is a power stroke followed by a return stroke. The picture to the left shows a close up of an unknown Paramecium species cell body. On either side of the cell body you should be able to make out a fuzzy boundary. These are the cilia beating very rapidly.

Ciliates are generally predators or bacterial feeders and the cilia as in the case of bacterial feeders such as Paramecium, sweep food particles into a gullet where they are taken into the cell in a vacuole. The darker clumps in the picture are food vacuoles in a very well fed Paramecium! A few ciliates have symbiotic algae or have "captured" chloroplasts and thus obtain energy either directly or indirectly from photosynthesis.



Ciliates come in a wide range of shapes from the slipper shaped Paramecium to stalked forms such as the Vorticella shown here. This a common ciliate often found attached to the surfaces of aquatic plants. The stalk has a contractile fiber running through its center and when disturbed, the organism retracts itself by contracting the stalk like a coiled spring.

The Ciliophora have complex cells and are characterized by having two different types of nuclei in their cells. The large macronucleus is specialized for protein synthesis and other day to day activities of the cell. The much smaller micronucleus is involved in reproductive activities. Some ciliates such as this Stentor, have multiple macronuclei Stentor has a series of bead-like macronucleii which are obvious enough to be visible with a light microscope without special staining.









The photomicrograph shows the oral region of an unidentified Stentor species with its crown of cirri, fused modified cilia. This particular species is about 400um when extended. Some Stentor get up to 2,000um and are quite visible to the unaided eye.







Paramecium, on the other hand, has a single large macronucleus and the small micronucleus is tucked up against it.

Created 6/12/99 revised 1/12/00 pgd

pgd revised 2/17/01