paramecium


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Related to paramecium: euglena

paramecium

(parəmē`sĭəm), unicellular organism of the genus Paramecium, of the ciliate phylum CiliophoraCiliophora
, phylum in the kingdom Protista consisting of the ciliates, or ciliophores, complex freshwater or saltwater protozoans that swim by the coordinated beating of their cilia—short, hairlike structures that cover the cell surface.
..... Click the link for more information.
 found in freshwater throughout the world. Like other protozoansprotozoan
, informal term for the unicellular heterotrophs of the kingdom Protista. Protozoans comprise a large, diverse assortment of microscopic or near-microscopic organisms that live as single cells or in simple colonies and that show no differentiation into tissues.
..... Click the link for more information.
, paramecia, previously considered one-celled animals, are now customarily placed in kingdom ProtistaProtista
or Protoctista
, in the five-kingdom system of classification, a kingdom comprising a variety of unicellular and some simple multinuclear and multicellular eukaryotic organisms.
..... Click the link for more information.
. The paramecium has a stiff outer covering that gives it a permanent slipper shape. It swims rapidly by coordinated wavelike beats of its many cilia—short, hairlike projections of the cell. A paramecium normally moves forward in a corkscrew fashion but is capable of reversing direction when it encounters adverse conditions. This trial-and-error behavior (backing up and then continuing forward in a slightly different direction until an optimum path is found) is conspicuous when the animal is observed through a microscope.

Paramecia and other ciliates are the most complex of all single-celled organisms. The paramecium has an external oral groove lined with cilia and leading to a mouth pore and gullet; food (typically smaller organisms, such as bacteria) is digested in food vacuoles. There are also an anal pore, two contractile vacuoles that regulate the water content of the cell, and two nuclei. The larger nucleus, or macronucleus, is thought to regulate most cell functions, while the smaller nucleus, or micronucleus, is involved in reproduction. Paramecia usually reproduce asexually by cell division but can also exchange genetic information via a process called conjugation, in which two individuals unite at the oral grooves and exchange micronuclei that serve as little packages of DNA, after which the cells divide, yielding daughter cells with DNA from each of the parents.

Bibliography

See A. Jurand and G. C. Selman, The Anatomy of Paramecium aurelia (1964).

Paramecium

 

a genus embracing the simplest organisms of the class Infusoria. The elongated oval body reaches a length of 0.3 mm. It has a thick external layer of cytoplasm, the pellicle, which consists of three membranes and is covered evenly with 10,000 to 15,000 cilia. The mouth is on the side, beneath the oral groove.

The species P. bursaria undergoes intracellular symbiosis with single-celled green algae, or zoochlorella. Two species, P. caudatum and P. aurelia, are widely used in laboratory experiments. Methods for reproducing paramecia are well developed.

paramecium

[‚par·ə′mē·sē·əm]
(invertebrate zoology)
A single-celled protozoan belonging to the family Parameciidae.

Paramecium

[‚par·ə′mē·sē·əm]
(invertebrate zoology)
The genus of protozoans composing the family Parameciidae.

paramecium

any freshwater protozoan of the genus Paramecium, having an oval body covered with cilia and a ventral ciliated groove for feeding: phylum Ciliophora (ciliates)
References in periodicals archive ?
Among them genus Paramecium of the oligohymenophorea ciliates is well studied in terms of its diversity, ultrastructure, physiology and genetics.
Only TRPP and TRPML have been reported in Bikonta species of the euglenozoans Leishmania and Trypanosoma and the alveolate protist Paramecium (Cai and Clapham, 2012; Arias-Darraz et al.
Supplemental melatonin in-creases clonal lifespan in the protozoan Paramecium tetraurelia.
A new approach for the assessment of acrylamide toxicity using a green paramecium.
Our discontent was real, but we were not alone: here was an ecologist manque who didn't peer down a microscope at the wild flagellations of the paramecium in a drop of slime, but someone who demanded you look at the whole picture, the woods, forests, soil, societies, all the interrelated living systems, methodically being destroyed before our very eyes, which no head of government, director of companies, scientist, academic or politician wished to address.
Recent support for this model has been demonstrated in the contractile infraciliary lattice of Paramecium where Sfi1-like proteins and various centrins mediate a calcium-responsive contraction of the cytoskeletal network (Gogendeau et al.
Paramecium Messiah Gesticulation" by Antler: A paramecium gesticulating as a cosmic prophet/in a drop of pondwater/warns other paramecia to beware/of delusions of grandeur.
O estudo de seres microscopicos, como Paramecium e algas, parte de uma situacao real/concreta e de vivencia cotidiana dos estudantes, e desse modo constitui um novo sentido para eles, pois na medida em que o ensino de ciencias leva em consideracao aspectos relacionados ao dia-a-dia, a significacao dos conceitos cientificos traz implicacoes sobre o proprio pensamento cotidiano, de modo que as pessoas possam perceber que ha diferentes formas de entender o mundo.
The "subhuman species" used in experiments with lower than ambient levels of radiation--a radiation "deficiency"--include alga, paramecium, shrimp, barley, rat, and mouse.