Notice the prominent food
vacuoles (red dye-filled spheres) seen in the photo. Ciliates have two types of nuclei, a macronucleus
and one or more micronuclei (see
Genetics). Other interesting cell
structures are their trichocysts (defense) and contractile vacuoles
(used for osmoregulation).
Click to enlarge
|Paramecium (Photo left by Y. Tsukii) is a unicellular eucaryote
belonging to the phylum Ciliophora, a taxonomic group that also includes Tetrahymena,
Stentor, Vorticella, and the human parasite Balantidium coli.
Ciliates are often motile by means of numerous cilia; in Paramecium these cilia
cover virtually the entire cell surface. Coordinated beating of the cilia
propels the cell and sweeps food particles (e.g. bacteria) into its oral
groove where food is then phagocytosed.
Paramecium is a favorite research
organisms of many scientists because it is easily cultured, can be grown in large numbers,
is readily accessible to microscopic and electrophysiological observation, and does not
pose the ethical dilemmas inherent in animal studies . In particular, our
research has focused on Paramecium's similarities to mammalian chemosensory nerve cells
(e.g. taste and smell receptors). As such, Paramecium is an excellent model
for studying the diverse aspects of chemical sensation and response: detection of a
chemical; change in cellular membrane potential; response to the stimulus .
One particular advantage of Paramecium is
that its swimming behavior - swim speed and turning frequency - are readily observable
and, since membrane voltage and swimming behavior are intricately linked, provides insight
into the cell's electrophysiology .
1. Van Houten, J., Trends Neurosci. 17:62-71, 1994.
2. Van Houten, J., Ann. Rev. Physiol. 54:639-663, 1992.
3. Kung, C. and Y. Saimi, Ann. Rev. Physiol. 44:519-534, 1982
This page was last edited on 08/14/03
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