The
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