Paramecium caudatum
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| Paramecium | ||||||||||
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| Paramecium caudatum Ehr. |
Paramecium caudatum [1] are unicellular organisms belonging to the genus of protozoa of the phylum Ciliophora[2]. They are less than 0.25mm in length and covered with minute hair-like projections called cilia[3] The cilia are used in locomotion and during feeding[2]. They are often called slipper animalcules because of their slipper-like shape[2].
They feed on bacteria which are driven into the gullet by the cilia[2]. Their natural habitat is fresh water[3]. They take in water by osmosis from the hypotonic environment, bladder-like contractile vacuoles accumulate the excess water from radial canals and periodically expel it through the plasma membrane by contractions of the surrounding cytoplasm[3]. The contractile vacuoles also serve to maintain osmotic pressure[2]. When moving through the water, they follow a spiral path while rotating on the long axis[2]. When a they encounter an obstacle, they exhibits the so-called avoidance reaction; it backs away at an angle and starts off in a new direction[2].
Paramecium have 2 nuclei (a large macronucleus and a single compact micronucleus)[4]. They cannot survive without macro-nucleus and cannot reproduce without micro-nucleus[3]. Reproduction is either by asexual binary fission or occasionally by conjugation (sexual)[3] and rarely by endomixis, a process involving total nuclear reorganization of individual organisms[2]. During binary fission a fully grown organism divides into two daughter cells[3]. Conjugation consists of the temporary union of 2 organisms and the exchange of micro-nuclear elements[3]. Without the rejuvenating effects of conjugation a paramecium ages and dies[3]. Only opposite mating types, or genetically compatible organisms, can unite in conjugation[3].
References
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