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Wikipedia / Testate amoebae

Testate amoebae (formerly thecamoebians, Testacea or Thecamoeba) are a polyphyletic group of unicellular amoeboid protists, which differ from naked amoebae in the presence of a test that partially encloses the cell, with an aperture from which the pseudopodia emerge, that provides the amoeba with shelter from predators and environmental conditions.

The test of some species is produced entirely by the amoeba and may be organic, siliceous or calcareous depending on the species (autogenic tests), whereas in other cases the test is made up of particles of sediment collected by the amoeba which are then agglutinated together by secretions from within the cell (xenogenic tests). A few taxa (Hyalospheniidae) can build either type, depending on the circumstances and availability of foreign material.

The assemblage referred to as "testate amoebae" is actually composed of several, unrelated groups of organisms. However, some features they all share that have been used to group them together include the presence of a test (regardless of its composition) and pseudopodia that do not anastomose.

Testate amoebae can be found in most freshwater environments, including lakes, rivers, cenotes, as well as mires and soils.

The strong and resistant nature of the tests allows them to be preserved long after the amoeba has died. These characteristics, along with the sensitivity that some species display to changes in environmental conditions (such as temperature, pH, and conductivity), has sparked their use as bioindicators and paleoclimate proxies in recent years.

Possible fossils of testate amoebae have been found from the Gaoyuzhuang Formation, which is almost 1.6 billion years old. This would make them among the earliest known fossils of protists. Unusually, no other testate fossils are known until the Tonian, over 600 million years later.

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Taxonomy and classification

Testate amoebae are a polyphyletic assemblage. The main testate amoebae groups are the lobose Tubulinea, which include Arcellinida, Difflugina and Phryganellina (within the Amoebozoa), and the filose Euglyphida (within the SAR supergroup), although there are smaller groups that also include other testate amoebae.

Order Arcellinida

  1. Family Arcellidae

Arcella - Ehrenberg 1832

  • Antarcella - Deflandre 1928

    1. Family Netzeliidae

    Netzelia - Ogden 1979

    1. Family Hyalospheniidae

    Quadrulella - Cockerell 1909

  • Hyalosphenia - Stein 1859

  • Alocodera - Jung 1942

  • Apodera - Loeblich & Tappan 1961

  • Certesella - Loeblich & Tappan 1961

  • Porosia - Jung 1942

  • Nebela - Leidy 1874

  • Padaungiella - Lara & Todorov 2012

    1. Family Microchlamyiidae

    Microchlamys - Cockerell 1911

  • Spumochlamys - Kudryavtsev & Hausmann 2007

    1. Family Plagiopyxidae

    Bullinularia - Deflandre 1953

  • Geoplagiopyxis - Chardez 1961

  • Protoplagiopyxis - Bonnet 1962

  • Paracentropyxis - Bonnet 1960

  • Plagiopyxis - Penard 1910

  • Hoogenraadia - Gauthier-Lievre & Thomas 1958

  • Planhoogenraadia - Bonnet 1977

    1. Family Cryptodifflugiidae

    Cryptodifflugia - Penard 1890

  • Wailesella - Deflandre 1928

    1. Family Microcoryciidae

    Amphizonella - Greeff 1866

  • Diplochlamys - Greeff 1888

  • Microcorycia - Cockerell 1911

  • Penardochlamys - Deflandre 1953

  • Zonomyxa - Nusslin 1882

  • Parmulina - Penard 1902

    1. Family Phryganellidae

    Phryganella - Penard 1902

    1. Family Lamtopyxidae

    Lamtopyxis - Bonnet 1974

    1. Family Distomatopyxidae

    Distomatopyxis - Bonnet 1964

    1. Family Paraquadrulidae

    Paraquadrula - Deflandre 1932

  • Lamtoquadrula - Bonnet 1974

    1. Family Centropyxidae

    Centropyxis - Stein 1857

  • Proplagiopyxis - Schonborn 1964

    1. Family Trigonopyxidae

    Trigonopyxis - Penard 1912

  • Cyclopyxis - Deflandre 1929

  • Geopyxella - Bonnet & Thomas 1955

  • Cornuapyxis - Couteaux and Chardez 1981

    1. Incertae sedis

    Argynnia - Vucetich 1974

  • Awerintzewia - Schouteden 1906

  • Cucurbitella - Penard 1902

  • Difflugia - Leclerc 1815

  • Geamphorella - Bonnet 1959

  • Heleopera - Leidy 1879

  • Jungia - Loeblich and Tappan 1961

  • Lagenodifflugia - Medioli & Scott 1983

  • Leptochlamys - West 1901

  • Lesquereusia - Schlumberger 1845

  • Maghrebia - Gauthier-Lievre & Thomas 1960

  • Mediolus - Patterson 2014

  • Microquadrula - Golemansky 1968

  • Oopyxis - Jung 1942

  • Pentagonia - Gauthier-Lievre & Thomas 1960

  • Physochila - Jung 1942

  • Pomoriella - Golemansky 1970

  • Pontigulasia - Rhumbler 1896

  • Protocucurbitella - Gauthier-Lievre & Thomas 1960

  • Pseudawerintzewia - Bonnet 1959

  • Pseudonebela - Gauthier-Lievre 1953

  • Pyxidicula - Ehrenberg 1838

  • Schoenbornia - Decloitre 1964

  • Schwabia - Jung 1942

  • Sexangularia - Awerintzew 1906

  • Suiadifflugia - Green 1975

  • Zivkovicia - Ogden 1987

  • Ellipsopyxis - Bonnet 1965

  • Ellipsopyxella - Bonnet 1975

    • Order Euglyphida

    1. Family Euglyphidae

    Euglypha - Dujardin, 1841

  • Scutiglypha - Foissner and Schiller, 2001

    1. Family Trinematidae

    Trinema - Dujardin 1841

  • Corythion - Taranek 1881

  • Puytoracia - Bonnet, 1970

  • Playfairina - Thomas 1961

  • Pileolus - Coûteaux and Chardez 1962

    1. Family Sphenoderiidae

    Sphenoderia - Schlumberger 1845

  • Trachelocorythion - Bonnet 1979

  • Deharvengia - Bonnet 1979

    1. Family Assulinidae

    Assulina - Leidy 1879

  • Placocista - Leidy 1879

  • Valkanovia - Tappan 1966

    1. Family Cyphoderiidae

    Cyphoderia - Schlumberger 1845

  • Corythionella - Golemansky 1970

  • Campascus - Leidy 1879

  • Messemvriella - Golemansky 1973

  • Pseudocorythion - Valkanov 1970

  • Schaudinnula - Awerintzev 1907

    1. Family Paulinellidae

    Paulinella - Lauterborn 1895

  • Ovulinata - Anderson, Rogerson & Hannah 1996

  • Micropyxidiella - Tarnawski & Lara 2015

    1. Incertae sedis

    Pareuglypha - Penard 1902

  • Ampullataria - Van Oye 1956

  • Euglyphidion - Bonnet 1960

  • Heteroglypha - Thomas and Gauthier-Lièvre 1959

  • Tracheleuglypha - Deflandre 1928

    • Other Cercozoa

    1. Family Chlamydophryidae

    Capsellina - Penard 1909

  • Lecythium - Hertwig and Lesser 1876

  • Rhogostoma - Belar 1921

  • Rhizaspis - Skuja 1948

  • Chlamydophrys - Cienkowsky 1876

  • Clypeolina - Cienkowsky 1877

  • Penardeugenia - Deflandre 1953

  • Leptochlamydophrys - Belar 1921

  • Diaphoropodon - Archer 1869

    1. Family Pseudodifflugiidae

    Pseudodifflugia - Schlumberger 1845

    1. Family Psammonobiotidae

    Alepiella - Golemansky 1970

  • Centropyxiella - Valkanov 1970

  • Chardezia - Golemansky 1970

  • Edaphonobiotus - Schönborn, Foissner & Meisterfeld 1983

  • Micramphora - Valkanov 1970

  • Micropsammella - Golemansky 1970

  • Nadinella - Penard 1902

  • Ogdeniella - Golemanski 1982

  • Psammonobiotus - Golemansky 1970

  • Propsammonobiotus - Golemansky 1991

    1. Incertae sedis

    Feuerbornia - Jung, 1942

  • Frenzelina - Penard 1902

  • Lesquerella - Chardez and Thomas, 1980

  • Matsakision - Bonnet, 1967

  • Rhumbleriella - Golemansky 1970

    • Order Stramenopila

    1. Family Amphitremidae

    Amphitrema - Archer 1869

  • Archerella - Loeblich and Tappan, 1961

    1. Family Diplophryidae

    Diplophrys - Barker 1868

    1. Family Amphifilidae

    Amphifila - Anderson and Cavalier-Smith 2012

    1. Family Sorodiplophryidae

    Sorodiplophris - Dykstra and Olive 1975

    • Unclassified testate amoebae

    • Paramphitrema - Valkanov 1970

    The following table includes a few examples of testate amoebae genera, and reflects their position within the classification by Adl et al. (2012), where five supergroups (Amoebozoa, Opisthokonta, Excavata, SAR and Archaeplastida) were proposed to classify all eukaryotes. This classification purposefully avoids the use of Linnaean higher category names (phylum, class, order, family). While it has been noted that the names that Adl et al. provide for the clades may result confusing or uninformative regarding the relative degree of phenotypic distinctiveness amongst groups when used in isolation, this system avoids creating superfluous ranks where unnecessary and provides stable group names that can be retained even when a group is moved to a different lineage, as is often the case with protists, as their classification remains in constant review.Traditionally, those species that form large networks of anastomosing pseudopodia, despite some of them having tests, are not counted amongst testate amoebae; this comprises genus Gromia and the Foraminifera (both in Rhizaria).

    Notes

    The Thecamoebida (Amoebozoa), with the genus Thecamoeba, despite their name, do not have tests.

    Euglyphid testate amoebae are closely related to the Foraminifera.

    • Microworld - World of ameboid organisms - A database of both testate and naked amoebae with over 6,700 microphotographs and videos and over 1,700 species descriptions, as well as dichotomous and visual keys for identification.

    References

    Bibliography