[[Image:Chaos diffluens.jpg|thumb|Amoeba (''Chaos diffluens'')]]
[[Image:live_Ammonia_tepida.jpg|thumb|Foraminiferan (''Ammonia tepida'')]]
[[Image:Actinophrys sol.jpg|thumb|Heliozoan (''Actinophrys sol'')]]
'''Amoeboids''' are [[cell (biology)|cell]]s that move or feed by means of temporary projections, called [[pseudopod]]s (false feet). They have appeared in a number of different groups. Some cells in multicellular animals may be amoeboid, for instance human [[white blood cell]]s, which consume pathogens. Many [[protist]]s exist as individual amoeboid cells, or take such a form at some point in their life-cycle. The most famous such organism is ''[[Amoeba|Amoeba proteus]]''; the name amoeba is variously used to describe its close relatives, other organisms similar to it, or the amoeboids in general.

Amoeboids may be divided into several morphological categories based on the form and structure of the pseudopods. Those where the pseudopods are supported by regular arrays of [[microtubule]]s are called actinopods, and forms where they are not are called rhizopods, further divided into lobose, filose, and reticulose amoebae. There is also a strange group of giant marine amoeboids, the [[xenophyophore]]s, that do not fall into any of these categories.

* Lobose pseudopods are blunt, and there may be one or several on a cell, which is usually divided into a layer of clear ectoplasm surrounding more granular endoplasm. Most, including ''Amoeba'' itself, move by the body mass flowing into an anterior pseudopod. The vast majority form a monophyletic group called the [[Amoebozoa]], which also includes most [[slime mould]]s. A second group, the [[Percolozoa]], includes protists that can transform between amoeboid and [[flagellate]] forms.

* Filose pseudopods are narrow and tapering. The vast majority of filose amoebae, including all those that produce shells, are placed within the [[Cercozoa]] together with various flagellates that tend to have amoeboid forms. The naked filose amoebae comprise two other groups, the [[vampyrellid]]s and [[nucleariid]]s. The latter appear to be close relatives of [[animal]]s and [[fungus|fungi]].

* Reticulose pseudopods are cytoplasmic strands that branch and merge to form a net. They are found most notably among the [[Foraminifera]], a large group of marine protists that generally produce multi-chambered shells. There are only a few sorts of naked reticulose amoeboids, notably the [[gymnophryid]]s, and their relationships are not certain.

* Actinopods are divided into the [[radiolaria]] and [[heliozoa]]. The radiolaria are mostly marine protists with complex internal skeletons, including central capsules that divide the cells into granular endoplasm and frothy ectoplasm that keeps them buoyant. The heliozoa include both freshwater and marine forms that use their axopods to capture small prey, and only have simple scales or spines for skeletal elements. Both groups appear to be [[polyphyletic]].

Traditionally the amoeboid protozoa are grouped together as the Sarcodina, variously ranked from class to phylum, with each of the above categories as a formal subtaxon. However, since they are all based on form rather than phylogeny, newer systems generally separate some out or abandon them entirely. Most amoeboids are now included in two major supergroups - the [[Amoebozoa]], including most lobose amoebae and slime moulds, and the [[Rhizaria]], including the Cercozoa, Foraminifera, radiolarian classes and certain heliozoa. However, amoeboids have appeared separately in many other groups, including various different lines of algae not listed above.

==Sub-phylum Sarcodina==
Amoeboids are classified in a sub-phylum called sarcodina. Basically, amoeboids move by moving their [[cytoplasm]], resembling limbs, to move around and engulf food particles with its cytoplasm. Some amoeba may form a glass covering around and over its normal amoeba body. When these protozoan die, their glass stays intact as the cytoplasm gradually dies. These glass particles then accumulate and are use to make many products, such as the luminosity of road paint, or the grit in toothpaste. Amoeboids mainly consist of [[contractile vacuoles]], a [[Cell nucleus|nucleus]], and cytoplasm as their basic structure. As the cytoplasm surrounds the prey, it injects [[enzymes]] into the organism, thus digesting their prey.

==External links==
* [http://www.bms.ed.ac.uk/research/others/smaciver/amoebae.htm The Amoebae] website brings together information from published sources.
* [http://www.microscopy-uk.org.uk/mag/wimsmall/sundr.html Amoebas are more than just blobs]
* [http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/wimsmall/sundr.html sun animacules and amoebas]
*[http://micro.magnet.fsu.edu/moviegallery/pondscum/protozoa/amoeba/index.html Molecular Expressions Digital Video Gallery: Pond Life - Amoeba (Protozoa)] Some good, informative Amoeba videos.
* [http://www.bairbrepaws.com/psneeley/FwrPLA.htm Joseph Leidy's Amoeba Plates]

[[Category:Protista]]
[[Category:Cell biology]]
[[Category:Amoeboids| ]]
[[Category:Motile cells]]

[[de:Amöbe]]
[[et:Juurjalgsed]]
[[es:Rizópodo]]
[[eu:Rhizopoda]]
[[fr:Rhizopoda]]
[[hr:Sarcodina]]
[[ja:肉質虫]]
[[pl:Korzenionóżki]]
[[sv:Amöbadjur]]
[[tr:Kökbacaklılar]]