Testate amoebae (formerly thecamoebians,

Testacea Testacea may refer to: * a former order of rhizopods, which consisted of testate amoeboid organisms. * a former group of shelled molluscs and other invertebrates, created by Linnaeus and roughly corresponding to the colloquial term '' seashell'' ...

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 A pseudopod or pseudopodium (plural: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filament ...

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 (Hyalosphenidae) 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 Paleolimnology (from Greek: παλαιός, ''palaios'', "ancient", λίμνη, ''limne'', "lake", and λόγος, ''logos'', "study") is a scientific sub-discipline closely related to both limnology and paleoecology. Paleolimnological studies fo ...

in recent years.

Gallery

File:Amoeba proteus 2.jpg, Naked amoeba (i. e. not testate) showing food vacuoles and ingested diatom File:Arcella sp.jpg, Shell or test of a testate amoeba, ''

Arcella ''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 with a hole on its center from where finger-like pseudopod ...

'' sp. File:Collection Penard MHNG Specimen 533-2-1 Pamphagus granulatus.tif,

Xenogenic A xenobiotic is a chemical substance found within an organism that is not naturally produced or expected to be present within the organism. It can also cover substances that are present in much higher concentrations than are usual. Natural compo ...

testate amoeba covered in diatoms (fro
Penard's Amoeba Collection
File:Euglypha tuberculata - Testate amoeba - 160x (14997753245).jpg, ''Euglypha tuberculata'', a species with a siliceous autogenic test File:Arcella sp (discoides) - 400x (14739877768).jpg, The autogenic test of ''Arcella discoides'', made up of organic plates File:Cyphoderia ampulla - Testate amoeba - 160x (14997391862).jpg, Shell of ''Cyphoderia ampulla'', composed of circular, siliceous plates produced by the amoeba

Taxonomy and classification

Testate amoebae are a polyphyletic assemblage. The main testate amoebae groups are the lobose Tubulinea, which include Arcellinida, Difflugina and

Phryganellina Arcellinid testate amoebae or Arcellinida,http://www.microscopy-uk.org.uk/mag/artjun03/gsamoebae.html Testate amoebae, peat bogs and past climates. accessed 16 march 2007 Arcellacean or lobose testate amoebae are single-celled protists partially ...

(within the

Amoebozoa Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, often possessing blunt, fingerlike, lobose pseudopods and tubular mitochondrial cristae. In traditional and currently no longer supported classi ...

), and the

filose Filose can refer to a few things: *Filose, describing members of the Filosa subphylum of Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead ...

Euglyphida (within the SAR supergroup), although there are smaller groups that also include other testate amoebae.

Order Arcellinida

;;Family Arcellidae * ''

'' - Ehrenberg 1832 * ''Antarcella'' - Deflandre 1928 ;;Family Netzeliidae * ''Netzelia'' - Ogden 1979 ;;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 ;;Family Microchlamyiidae * ''Microchlamys'' - Cockerell 1911 * ''Spumochlamys'' - Kudryavtsev & Hausmann 2007 ;;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 ;;Family Cryptodifflugiidae * '' Cryptodifflugia'' - Penard 1890 * ''Wailesella'' - Deflandre 1928 ;;Family Microcoryciidae * ''Amphizonella'' - Greeff 1866 * '' Diplochlamys'' - Greeff 1888 * ''Microcorycia'' - Cockerell 1911 * ''Penardochlamys'' - Deflandre 1953 * ''Zonomyxa'' - Nusslin 1882 * ''Parmulina'' - Penard 1902 ;;Family Phryganellidae * ''Phryganella'' - Penard 1902 ;;Family Lamtopyxidae * ''Lamtopyxis'' - Bonnet 1974 ;;Family Distomatopyxidae * ''Distomatopyxis'' - Bonnet 1964 ;;Family Paraquadrulidae * ''Paraquadrula'' - Deflandre 1932 * ''Lamtoquadrula'' - Bonnet 1974 ;;Family Centropyxidae * '' Centropyxis'' - Stein 1857 * ''Proplagiopyxis'' - Schonborn 1964 ;;Family Trigonopyxidae * ''Trigonopyxis'' - Penard 1912 * ''Cyclopyxis'' - Deflandre 1929 * ''Geopyxella'' - Bonnet & Thomas 1955 * ''Cornuapyxis'' - Couteaux and Chardez 1981 ;;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

;;Family Euglyphidae * '' Euglypha'' - Dujardin, 1841 * ''Scutiglypha'' - Foissner and Schiller, 2001 ;;Family Trinematidae * '' Trinema'' - Dujardin 1841 * ''Corythion'' - Taranek 1881 * ''Puytoracia'' - Bonnet, 1970 * ''Playfairina'' - Thomas 1961 * ''Pileolus'' - Coûteaux and Chardez 1962 ;;Family Sphenoderiidae * ''Sphenoderia'' - Schlumberger 1845 * ''Trachelocorythion'' - Bonnet 1979 * ''Deharvengia'' - Bonnet 1979 ;;Family Assulinidae * ''Assulina'' - Leidy 1879 * ''Placocista'' - Leidy 1879 * ''Valkanovia'' - Tappan 1966 ;;Family Cyphoderiidae * '' Cyphoderia'' - Schlumberger 1845 * ''Corythionella'' - Golemansky 1970 * ''Campascus'' - Leidy 1879 * ''Messemvriella'' - Golemansky 1973 * ''Pseudocorythion'' - Valkanov 1970 * ''Schaudinnula'' - Awerintzev 1907 ;;Family Paulinellidae * '' Paulinella'' - Lauterborn 1895 * ''Ovulinata'' - Anderson, Rogerson & Hannah 1996 * ''Micropyxidiella'' - Tarnawski & Lara 2015 ;;Incertae sedis * ''Pareuglypha'' - Penard 1902 * ''Ampullataria'' - Van Oye 1956 * ''Euglyphidion'' - Bonnet 1960 * ''Heteroglypha'' - Thomas and Gauthier-Lièvre 1959 * ''Tracheleuglypha'' - Deflandre 1928

Other Cercozoa

;;Family Chlamydophryidae * ''Capsellina'' - Penard 1909 * ''

Lecythium ''Lecythium'' is a genus of 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 en ...

'' - 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 ;;Family Pseudodifflugiidae * ''

Pseudodifflugia ''Pseudodifflugia'' is a genus of Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or ...

'' - Schlumberger 1845 ;;Family Psammonobiotidae * ''Alepiella'' - Golemansky 1970 * ''

Centropyxiella ''Centropyxiella'' is a genus of Amoebozoa in the family Centropyxidae Centropyxidae is a family of Amoebozoa Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, often possessing blunt, fingerl ...

'' - 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 ;;Incertae sedis * ''Feuerbornia'' - Jung, 1942 * ''Frenzelina'' - Penard 1902 * ''Lesquerella'' - Chardez and Thomas, 1980 * ''Matsakision'' - Bonnet, 1967 * ''Rhumbleriella'' - Golemansky 1970

Order Stramenopila

;;Family Amphitremidae * ''

Amphitrema ''Amphitrema'' is a genus of testate amoeba in the family Amphitremidae. The genus is commonly found in ''Sphagnum''-dominated peatlands. All species of this genus are mixotrophic and harbor unicellular algae belonging to genus ''Chlorella ...

'' - Archer 1869 * ''Archerella'' - Loeblich and Tappan, 1961 ;;Family Diplophryidae * ''Diplophrys'' - Barker 1868 ;;Family Amphifilidae * ''Amphifila'' - Anderson and Cavalier-Smith 2012 ;;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 (

, Opisthokonta, Excavata,

SAR SAR or Sar may refer to: Places * Sar (river), Galicia, Spain * Sar, Bahrain, a residential district * Sar, Iran (disambiguation), several places in Iran * Sar, Tibet, Tibet Autonomous Region of China * Šar Mountains, in southeastern Europe ...

and Archaeplastida) were proposed to classify all

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

s. 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 Lineage may refer to: Science * Lineage (anthropology), a group that can demonstrate its common descent from an apical ancestor or a direct line of descent from an ancestor * Lineage (evolution), a temporal sequence of individuals, populati ...

, as is often the case with protists, as their classification remains in constant review. Traditionally, those species that form large networks of anastomosing

, 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.

External links

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

{{Wikispecies, Testacea * Medioli, F.S.; Scott, D.B.; Collins, E.; Asioli, S.; Reinhardt, E.G. (1999). The thecamoebian bibliography. ''Palaeontologia Electronica'', 3: 1-161

* Medioli, F.S.; Bonnet, L.; Scott, D.B.; Medioli, B.E. (2003). The thecamoebian bibliography: 2nd edition. ''Palaeontologia Electronica'', 61: 1-107

Amoeboids