Testate amoebae (thecamoebians, formally Testacea or Thecamoeba) are a polyphyletic group of unicellular ameboid protists, which differ from naked amoebae in the presence of a test that partially encloses the cell, from which the pseudopodia emerge, and that provides the cell with shelter from predators and environmental conditions.
The test of some species is made up of particles of sediment where the amoebae live, which are agglutinated together by secretions from within the cell, whereas in other cases the test is produced entirely by the amoeba and may be organic, siliceous or calcareous depending on the species.
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.[1]
Testate amoebae can be found in most freshwater environments, including lakes, rivers, cenotes[2], 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. This, as well as 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.[3]
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)[4], and the filose Euglyphida (within the SAR supergroup)[5], although there are smaller groups that also include other testate amoebae.[6]
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 Stein 1857
Proplagiopyxis Schonborn 1964
- Family Trigonopyxidae
Trigonopyxis Penard 1912
Cyclopyxis Deflandre 1929
Geopyxella Bonnet & Thomas 1955
Cornuapyxis Couteaux and Chardez 1981
- Incertae sedis
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
The following table includes a few examples of testate amoebae genera, and reflects the classification by Adl et al. (2012)[6], 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[7], 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.[6]
| Amoebozoa | Tubulinea | Arcellinida | Arcellina | Amphizonella - Arcella - Microchlamys - Microcorycia - Spumochlamys | |||
|---|---|---|---|---|---|---|---|
| Difflugina | Bullinularia - Centropyxis - Difflugia - Distomatopyxis - Heleopera - Hyalosphenia - Lesquereusia - Nebela - Paraquadrula - Pontigulasia -
Plagiopyxis - Quadrulella - Trigonopyxis | ||||||
| Phryganellina | Cryptodifflugia - Phryganella - Wailesella | ||||||
| Discosea | Himatismenida | Cochliopodium | |||||
| SAR Supergroup | Stramenopila | Labyrinthulomycetes | Amphitremida | Amphitrema - Archerella | |||
| Rhizaria | Cercozoa | Thecofilosea | Cryomonadida | Rhizaspididae | Capsellina - Rhizaspis - Rhogostoma | ||
| Ventricleftida | Ventrifissura - Verrucomonas | ||||||
| Imbricatea | Silicofilosea | Euglyphida | Euglyphidae | Euglypha - Scutiglypha | |||
| Assulinidae | Assulina - Placocista - Valkanovia | ||||||
| Trinematidae | Corythion - Playfairina - Puytoracia - Trinema | ||||||
| Cyphoderidae | Campascus - Corythionella - Cyphoderia - Messemvriella - Pseudocorythion - Schaudinnula. | ||||||
| Paulinellidae | Ovulinata - Paulinella | ||||||
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).[1]
Notes
The Thecamoebida (Amoebozoa), with the genus Thecamoeba, despite their name, do not have tests.
Euglyphid testate amoebae are closely related to the Foraminifera.[8]
See also
- 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
- ^ a b Kosakyan, Anush; Gomaa, Fatma; Lara, Enrique; Lahr, Daniel J.G. "Current and future perspectives on the systematics, taxonomy and nomenclature of testate amoebae". European Journal of Protistology. 55: 105–117. doi:10.1016/j.ejop.2016.02.001.
- ^ Sigala, Itzel; Lozano-García, Socorro; Escobar, Jaime; Pérez, Liseth; Gallegos-Neyra, Elvia (2016-06-28). "Testate Amoebae (Amebozoa: Arcellinida) in Tropical Lakes of Central Mexico". Revista de Biología Tropical. 64 (1): 377–397. doi:10.15517/rbt.v64i1.18004. ISSN 2215-2075.
- ^ Mitchell, Edward A. D.; Charman, Daniel J.; Warner, Barry G. (2008-08-01). "Testate amoebae analysis in ecological and paleoecological studies of wetlands: past, present and future". Biodiversity and Conservation. 17 (9): 2115–2137. doi:10.1007/s10531-007-9221-3. ISSN 0960-3115.
- ^ Ralf Meisterfeld: Arcellinida, In: John J. Lee, Gordon F. Leedale, Phyllis Bradbury (Hrsg.): Illustrated Guide to the Protozoa, 2nd Edition. Vol. 2, Society of Protozoologists, Lawrence, Kansas 2000, ISBN 1-891276-23-9, pp. 827-860
- ^ Ralf Meisterfeld: Testate amoebae with filopodia , In: John J. Lee, Gordon F. Leedale, Phyllis Bradbury (Hrsg.): The Illustrated Guide to the Protozoa, 2nd Edition. Vol. 2, Society of Protozoologists, Lawrence, Kansas 2000, ISBN 1-891276-23-9, pp. 1054-1084
- ^ a b c Adl, Sina M.; Simpson, Alastair G. B.; Lane, Christopher E.; Lukeš, Julius; Bass, David; Bowser, Samuel S.; Brown, Matthew W.; Burki, Fabien; Dunthorn, Micah (2012-09-01). "The Revised Classification of Eukaryotes". Journal of Eukaryotic Microbiology. 59 (5): 429–514. doi:10.1111/j.1550-7408.2012.00644.x. ISSN 1550-7408.
- ^ Ruggiero, Michael A.; Gordon, Dennis P.; Orrell, Thomas M.; Bailly, Nicolas; Bourgoin, Thierry; Brusca, Richard C.; Cavalier-Smith, Thomas; Guiry, Michael D.; Kirk, Paul M. (2015-04-29). "A Higher Level Classification of All Living Organisms". PLOS ONE. 10 (4): e0119248. doi:10.1371/journal.pone.0119248. ISSN 1932-6203.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Testate amoebae as environmental indicators (PDF)
Bibliography
- Medioli, F.S.; Scott, D.B.; Collins, E.; Asioli, S.; Reinhardt, E.G. (1999). The thecamoebian bibliography. Palaeontologia Electronica, 3: 1-161, [1].
- Medioli, F.S.; Bonnet, L.; Scott, D.B.; Medioli, B.E. (2003). The thecamoebian bibliography: 2nd edition. Palaeontologia Electronica, 61: 1-107, [2].