''Arcella'' is a genus of testate amoebae in the order Arcellinida, usually found in freshwaters and mosses, and rarely in soils. A key characteristic of ''Arcella'' is the circular Test (biology), test with a hole on its center from where finger-like pseudopods emerge. It is one of the largest testacean genera.

Anatomy

An ''Arcella'' is typically enclosed in a chitinous, umbrella-shaped Test (biology), test (or shell) that has a single central aperture through which the pseudopods – which are used for locomotion – extend out. In some species the aperture is surrounded by a ring of pores. The test is composed of organic material with a diameter of up to 300 µm and is transparent or light-yellow-colored in young ''Arcella'', but browns while aging due to the progressive deposition of iron and manganese compounds.Ralf Meisterfeld and Edward Mitchell (2008)
"''Arcella'' Ehrenberg 1832"
Contrary to other genera, no gravel chips or other foreign bodies are inserted to strengthen the housing. Different species of ''Arcella'' can have different number of nuclei, ranging from a single nucleus, as in some ''Arcella hemisphaerica, A. hemisphaerica'', up to 200 nuclei, as in ''Arcella megastoma, A. megastoma'', though the majority is binucleate. They also have many contractile vacuoles, and can develop vacuoles of carbon dioxide in their cytoplasm to float up to the surface of the water.

Nutrition and distribution

''Arcella'' inhabit freshwater pools, eutrophic waters, marshes, mosses, as well as wet foliage. Few species can also be found in soils. They nourish on diatoms, unicellular green algae or animal protozoa such as flagellates and ciliates. Most species are worldwide-distributed, but some have restricted distributions, e.g. ''A. brasiliensis'' and ''A. rota'' which are endemic to South America. They eat by stretching out their pseudopods to surround the food and bring it back to the microorganism.

Species

Over 130 species and subspecies of the genus ''Arcella'' have been described so far. Species include: *''Arcella arenaria'' Greeff, 1866
Microworld Arcella *''Arcella artocrea'' Leidy, 1876 *''Arcella brasiliensis'' Cunha, 1913 *''Arcella catinus'' Penard, 1890 *''Arcella conica'' (Playfair, 1918) * ''Arcella costata'' Ehrenberg, 1847 *''Arcella dentata'' Ehrenberg, 1830 *''Arcella discoides'' Ehrenberg, 1843 ** ''Arcella discoides var. scutelliformis'' Playfair, 1918 *''Arcella excavata'' Cunningham, 1919
* Arcella gandalfi Féres et al., 2016 Microworld
/ref> *''Arcella gibbosa'' Penard, 1890 *''Arcella hemisphaerica'' Perty, 1852 * ''Arcella intermedia'' (Deflandre, 1928) Tsyganov & Mazei 2006 *''Arcella megastoma'' Penard, 1902 * ''Arcella mitrata'' Leidy, 1876 * ''Arcella multilobata'' Golemansky, 1964 * ''Arcella ovaliformis'' Chardez and Beyens, 1987 * ''Arcella rota'' Daday, 1905 *''Arcella peruviana'' Reczuga et al., 2015 * ''Arcella rotundata'' Playfair, 1918 *''Arcella vulgaris'' Ehrenberg, 1830

References

External links

{{Taxonbar, from=Q971534 Amoebozoa genera Tubulinea Taxa named by Christian Gottfried Ehrenberg