Paramecium
Unicellular ciliates widely used as model organisms.
Paramecium is a genus of eukaryotic, unicellular ciliates found in freshwater, brackish, and marine environments, often abundant in stagnant basins and ponds. Because some species are readily cultivated and easily induced to conjugate and divide, they have been widely used in classrooms and laboratories to study biological processes, and have been characterized as the 'white rats' of the phylum Ciliophora.
- field
- Microbiology, Protozoology
- known_for
- Model organism among ciliates; first ciliates observed by microscopists in the late 17th century
- size_range
- 0.06 mm to 0.3 mm in length
- habitat
- Freshwater, brackish, and marine environments
Lore & Background
Paramecium were among the first ciliates to be observed by microscopists, in the late 17th century. F. C. G.
Reader's Guide
Paramecium species have served as key model organisms in biology, particularly for studying ciliate structure, movement, and reproduction. Their ciliary locomotion, which involves coordinated waves of effective and recovery strokes, has been calculated to be less than 1% efficient, yet close to the theoretical maximum for cilia of their length. The genus has also been central to research on endosymbiosis, with species like Paramecium bursaria harboring green algae, and on bacterial endosymbionts such as kappa particles that confer killer traits. The genome of Paramecium tetraurelia has been sequenced, revealing evidence for three whole-genome duplications, and the genus exhibits an unusual genetic code where UGA is the only stop codon. Their ease of cultivation and sexual phenomena like conjugation have made them enduring tools in classrooms and laboratories.
Did You Know?
- Some species, like Paramecium bursaria, form mutualistic relationships with endosymbiotic green algae.
- In Paramecium, only UGA is decoded as a stop codon; UAG and UAA code for glutamic acid.
More in Algae & Protists 1-19
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