amoeba

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Related to amoebae: paramecia, paramecium, Ciliates, Entamoeba histolytica, Naegleria fowleri

amoeba:

see amebaameba
or amoeba
, common name for certain one-celled organisms belonging to the phylum Sarcodina of the kingdom Protista. Amebas were previously classified as members of the animal kingdom.
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Amoeba

 

the order of the simplest organized protozoa of the class Sarcodina. Most live in fresh waters, a few in the soil; there are parasitic forms. They are usually of microscopic dimensions up to 50 μm, but there are also “giants” such as Pelomyxa, which grows to 2–3 mm. Amoebas have no constant body shape; their cytoplasmic body forms extrusions or pseudopodia which aid in motion and food gathering. They feed on bacteria, minute algae, and protozoa. The amoeba engulfs the food particle and from its cytoplasm the amoeba secretes digestive juices and forms a food vacuole within which the food is dissolved and is incorporated into the cytoplasm. The excretion of water (osmoregulation) and metabolic products occurs through the contractory vacuoles, which gradually accumulate waste matter and discharge it at the surface.

Amoebas ordinarily have one nucleus, but Pelomyxa is multinucleate. The majority of amoebas multiply asexually, dividing in two. The division of the body is preceded by mitosis in the nucleus. A sexual process is known only in very rare cases.

Upon subjection to unfavorable conditions—for instance, insufficient food, cold, or drying of the water body—the amoeba’s body becomes round and the surface of its cytoplasm becomes a dense protective layer; a cyst forms that is resistant to unfavorable effects of the dormant stage. Freshwater amoebas can serve as a water pollution index. Parasitic amoebas live in the intestines of various animals and man. Among these the most harmful is the dysentery amoeba (Entamoeba histolytica), which produces a severe form of amoebic dysentery in man. Infection occurs via cysts, which remain viable outside the human body.

REFERENCES

Dogel’, V. A., Iu. I. Polianskii, and E. M. Kheisin. Obshchaia protozoologiia. Moscow-Leningrad, 1962.
Seravin, L. N. Dvigatel’nye sistemy prosteishikh. Leningrad, 1967.

A. A. STRELKOV

Amoeba

[ə′mē·bə]
(invertebrate zoology)
A genus of naked, rhizopod protozoans in the order Amoebida characterized by a thin pellicle and thick, irregular pseudopodia.

amoeba

(US), ameba
any protozoan of the phylum Rhizopoda, esp any of the genus Amoeba, able to change shape because of the movements of cell processes (pseudopodia). They live in fresh water or soil or as parasites in man and animals

Amoeba

(operating system)
A distributed operating system developed by Andrew S. Tanenbaum and others of Vrije Universiteit, Amsterdam. Amoeba is only available under licence from the VUA, but is free of charge and includes all source, binaries and documentation.

http://am.cs.vu.nl/.

Amoeba

(computer, abuse)
A derogatory term for Commodore's Amiga personal computer.
References in periodicals archive ?
The Mnemiopsis amoebae thus appear move to novel environments with the host.
All samples were washed through a coarse sieve (about 750 [micro]m) into a boiling glass and the testate amoebae and peat debris were let to deposit for several hours.
If amoebae occur in well-mixed cosmopolitan groups, then cheaters will always be able to thrive by freeloading on their cooperative neighbors.
The amoebae were fed with live (monoaxenic) and heat killed (axenic) suspensions as stated earlier and incubated.
The study, conducted by evolutionary biologists Joan Strassmann and David Queller of Rice University, has shown that long-studied social amoebae Dictyostellum discoideum (commonly known as slime molds) increase their odds of survival through a rudimentary form of agriculture.
The amoebae follow their prey and then ingest it by forming cytoplasmic extensions"--otherwise known as "false feet"--which engulf and funnel the hapless captives into food vacuoles for digestion.
noveboracensis in the understory of deciduous trees in the forest reserve at Torrey Cliff, NY to document the rhizosphere (root-associated) density of commonly occurring heterotrophic eukaryotic microbes (protozoa), including microflagellates, naked amoebae and testate amoebae.
Primers to conserved SSU rRNA sequences of parasome-containing amoebae and their nonparasome-containing relatives were used to amplify overlapping SSU rRNA fragments of the presumptive parasite from gill, antenna, antennal gland and ventral nerve cord of infected lobsters.
Free-living amoebae have been isolated worldwide from soil, water, air (1), and from the noses of healthy persons (2,3).
Targeted to scientists, researchers and academics, the journal carries reports of basic research on eukaryotic microorganisms such as yeasts, fungi, algae, protozoa and social amoebae.
Amoebae, bacteria, viruses and fungi are also living parasites of the body that we willingly abort without moral condemnation.