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 A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

group of unicellular

amoeboid An amoeba (; less commonly spelled ameba or amœba; : amoebas (less commonly, amebas) or amoebae (amebae) ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and r ...

protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...

s, which differ from naked amoebae in the presence of a

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film) ...

that partially encloses the cell, with an aperture from which the

pseudopodia A pseudopod or pseudopodium (: 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 filaments and ...

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 An anastomosis (, : anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be normal (su ...

. Testate amoebae can be found in most freshwater environments, including lakes, rivers,

cenote A cenote ( or ; ) is a natural pit, or sinkhole, resulting when a collapse of limestone bedrock exposes groundwater. The term originated on the Yucatán Peninsula of Mexico, where the ancient Maya commonly used cenotes for water supplies, and ...

s, as well as

mire A peatland is a type of wetland whose soils consist of Soil organic matter, organic matter from decaying plants, forming layers of peat. Peatlands arise because of incomplete decomposition of organic matter, usually litter from vegetation, du ...

s 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

bioindicator A bioindicator is any species (an indicator species) or group of species whose function, population, or status can reveal the qualitative status of the environment. The most common indicator species are animals. For example, copepods and other sma ...

s and paleoclimate proxies 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'' 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 The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', '' Arcella'', '' Difflugia'' and '' Hartmannella''. Characteristics During locomotion most Tubulinea have a roughly cylindrica ...

, 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 Taxonomy (biology), taxonomic group containing about 2,400 described species of Amoeba, amoeboid protists, often possessing blunt, fingerlike, Pseudopod#Morphology, lobose pseudopods and tubular mitochondrial cristae. In trad ...

), and the

filose Cercozoa (now synonymised with Filosa) is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead united by molecular phylogenies of rRNA and actin or polyubiquitin. ...

Euglyphida (within the

SAR supergroup SAR is a highly diverse clade of eukaryotes, often considered a supergroup, that includes stramenopiles (heterokonts), alveolates, and rhizarians. It is a node-based taxon (under the Sar name), including all descendants of the three groups' ...

), although there are smaller groups that also include other testate amoebae.

Order Arcellinida

;;Family Arcellidae * '' Arcella'' - 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 ''Centropyxis'' is a genus of lobose testate amoebae (Amoebozoa), including the species ''Centropyxis aculeata''. References External links Descriptions and pictures of Centropyxis
' at Microworld Amoebozoa genera Taxa named by Johann ...

'' - 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 ''Euglypha'' is a genus of cercozoa. It includes the species ''Euglypha rotunda''. References External links

* * Imbricatea Rhizaria genera {{Cercozoa-stub ...

'' - 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 ''Paulinella'' is a genus of at least eleven species including both freshwater and marine amoeboids. Like many members of euglyphids it is covered by rows of siliceous scales, and use filose pseudopods to crawl over the substrate of the benthi ...

'' - 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'' - 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 Endomyxa. It was described in 1845. References Rhizaria genera {{Cercozoa-stub ...

'' - Schlumberger 1845 ;;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 ;;Incertae sedis * ''Feuerbornia'' - Jung, 1942 * ''Frenzelina'' - Penard 1902 * ''Lesquerella'' - Chardez and Thomas, 1980 * ''Matsakision'' - Bonnet, 1967 * ''Rhumbleriella'' - Golemansky 1970

Order Stramenopila

;;Family Amphitremidae * '' Amphitrema'' - 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 (

Opisthokont The opisthokonts () are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and ...

Excavata Excavata is an obsolete, extensive and diverse paraphyletic group of unicellular Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains ...

, SAR and

Archaeplastida The Archaeplastida (or kingdom Plantae '' sensu lato'' "in a broad sense"; pronounced ) are a major group of eukaryotes, comprising the photoautotrophic red algae (Rhodophyta), green algae, land plants, and the minor group glaucophytes. It als ...

) were proposed to classify all

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

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 In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

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

, despite some of them having tests, are not counted amongst testate amoebae; this comprises genus ''

Gromia ''Gromia'' is a genus of protists, closely related to foraminifera, which inhabit marine and freshwater environments. It is the only genus of the family Gromiidae. ''Gromia'' are ameboid, producing filose pseudopodia that extend out from the cel ...

'' and the

Foraminifera Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...

(both in Rhizaria).

Notes

The

Thecamoebida Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, a t ...

(Amoebozoa), with the genus ''

Thecamoeba ''Thecamoeba ''is a genus of Amoebozoa Amoebozoa is a major Taxonomy (biology), taxonomic group containing about 2,400 described species of Amoeba, amoeboid protists, often possessing blunt, fingerlike, Pseudopod#Morphology, lobose pseudopods ...

'', despite their name, do not have tests. Euglyphid testate amoebae are closely related to the

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