Rhizaria
| Rhizaria Temporal range: | |
|---|---|
| |
| Ammonia tepida (Foraminifera) | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | TSAR |
| Clade: | SAR |
| Clade: | Rhizaria Cavalier-Smith, 2002 |
| Phyla[2] | |
The Rhizaria are a diverse and species-rich supergroup of mostly unicellular[3] eukaryotes.[4] Except for the Chlorarachniophytes and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthetic, but many Foraminifera and Radiolaria have a symbiotic relationship with unicellular algae.[5] A multicellular form, Guttulinopsis vulgaris, a cellular slime mold, has been described.[6] This group was used by Cavalier-Smith in 2002, although the term "Rhizaria" had been long used for clades within the currently recognized taxon.
Being described mainly from rDNA sequences, they vary considerably in form, having no clear morphological distinctive characters (synapomorphies), but for the most part they are amoeboids with reticulose, or microtubule-supported pseudopods. In the absence of an apomorphy, the group is ill-defined, and its composition has been very fluid. Some Rhizaria possess mineral exoskeletons (thecae or loricas), which are in different clades within Rhizaria made out of opal (SiO2), celestite (SrSO4), or calcite (CaCO3).
Certain species can attain sizes of more than a centimeter with some species being able to form cylindrical colonies approximately 1 cm in diameter and greater than 1 m in length. They feed by capturing and engulfing prey with the extensions of their pseudopodia; forms that are symbiotic with unicellular algae contribute significantly to the total primary production of the ocean.[7]
Groups
[edit]The three main groups of Rhizaria are:[8]
- Cercozoa – various amoebae and flagellates, usually with filose pseudopods and common in soil
- Foraminifera – amoeboids with reticulose pseudopods, common as marine benthos
- Radiolaria – amoeboids with axopods, common as marine plankton
A few other groups may be included in the Cercozoa, but some trees appear closer to the Foraminifera. These are the Phytomyxea and Ascetosporea, parasites of plants and animals, respectively, and the peculiar amoeba Gromia. The different groups of Rhizaria are considered close relatives based mainly on genetic similarities, and have been regarded as an extension of the Cercozoa. The name Rhizaria for the expanded group was introduced by Cavalier-Smith in 2002,[9] who also included the centrohelids and Apusozoa.
A noteworthy order that belongs to Ascetosporea is the Mikrocytida.[10] These are parasites of oysters. This includes the causative agent of Denman Island Disease, Mikrocytos mackini a small (2−3 μm diameter) amitochondriate protistan.[11]
History
[edit]Similarities between various Rhizaria organisms have been noticed since the 19th century. In his 1861 classification of the Rhizopoda (amoebae), the zoologist William B. Carpenter proposed the order Reticularia, which consisted of Foraminifera and Gromiida on the basis of their very similar thin, reticulose pseudopodia with granules circulating inside.[12] However, the idea that these organisms and others such as Radiolaria were all related to one another emerged rather recently, with the help of molecular phylogenetics and advanced microscopy techniques in the late 20th century.[13]
Evolutionary relationships
[edit]Rhizaria are part of the SAR supergroup (Stramenopiles, Alveolates, Rhizaria), a grouping that had been presaged in 1993 through a study of mitochondrial morphologies.[14] SAR is currently placed in the Diaphoretickes along with Archaeplastida, Cryptista, Haptista, and several minor clades.
Historically, many rhizarians were considered animals because of their motility and heterotrophy. However, when a simple animal-plant dichotomy was superseded by a recognition of additional kingdoms, taxonomists generally placed amoebae in the kingdom Protista. When scientists began examining the evolutionary relationships among eukaryotes in the 1970s, it became clear that the kingdom Protista was paraphyletic. Rhizaria appear to share a common ancestor with Stramenopiles and Alveolates forming part of the SAR super assemblage.[15] Rhizaria has been supported by molecular phylogenetic studies as a monophyletic group.[16] Biosynthesis of 24-isopropyl cholestane precursors in various rhizaria[17] suggests a relevant ecological role already during the Ediacaran.
Phylogeny
[edit]Rhizaria is a monophyletic group composed of two sister phyla: Cercozoa and Retaria. Subsequently, Cercozoa and Retaria are also monophyletic.[18][19] The following cladogram depicts the evolutionary relationships between all rhizarian classes, and is made after the works of Cavalier-Smith et al. (2018),[1] and Irwin et al. (2019).[20]
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Sexual cycle
[edit]Complete sexual life cycles have been demonstrated for two lineages (Foraminifera and Gromia) and direct evidence for karyogamy or meiosis has been observed in five lineages (Euglyphida, Thecofilosea, Chlorarachniophyta, Plasmodiophorida and Phaeodarea).[21] In particular, the Foraminifera are marine amoebae that are defined by a dynamic network of pseudopodia, and the production of intricate shells.[21] These amoeba have complex sexual life cycles with meiosis and gamete production occurring at separate stages.[21]
References
[edit]- ^ a b Cavalier-Smith, Thomas; Chao, Ema E .; Lewis, Rhodri (April 2018). 29666938.
- ^ Sina M. Adl; David Bass; Christopher E. Lane; et al. (1 January 2019). 6492006. PMID Q57086550.
- ^ Taylor, Christopher (2004). the original on 2009-04-20.
- ^ Nikolaev, Sergey I.; Berney, Cédric; Fahrni, José F.; et al. (May 2004). 15148395.
- ^ Gast, Rebecca J.; Caron, David A. (2001-10-01). "Photosymbiotic associations in planktonic foraminifera and radiolaria". Hydrobiologia. 461 (1): 1–7. doi:1387879.
- ^ Brown, Matthew W.; Kolisko, Martin; Silberman, Jeffrey D.; Roger, Andrew J. (June 2012). 22608512.
- ^ Caron DA (April 2016). "Ocean science: The rise of Rhizaria". Nature. 532 (7600): 444–5. Bibcode:27096370.
- ^ Moreira D, von der Heyden S, Bass D, López-García P, Chao E, Cavalier-Smith T (July 2007). "Global eukaryote phylogeny: Combined small- and large-subunit ribosomal DNA trees support monophyly of Rhizaria, Retaria and Excavata". Mol. Phylogenet. Evol. 44 (1): 255–66. Bibcode:17174576.
- ^ Cavalier-Smith, Thomas (2002). 11931142.
- ^ Hartikainen, H.; Stentiford, G.D.; Bateman, K.S.; Berney, C.; Feist, S.W.; Longshaw, M.; Okamura, B.; Stone, D.; Ward, G.; Wood, C.; Bass, D. (2014). 24656829. S2CID 17180719.
- ^ Hine, P.M.; Bower, S.M.; Meyer, G.R.; Cochennec-Laureau, N.; Berthe, F.C.J. (2001). 11558731.
- ^ Carpenter, William Benjamin (1861). "XLVII.-On the systematic arrangement of the Rhizopoda". Natural History Review (Dublin and London). 1 (4): 478.
- ^ Burki F, Keeling PJ (February 2014). 24502779.
- ^ Seravin LN (1993). "[The basic types and forms of the fine structure of mitochondrial cristae: the degree of their evolutionary stability (capacity for morphological transformations)]". Tsitologiia (in Russian). 35 (4): 3–34. PMID 8328023.
- ^ Burki, F.; Shalchian-Tabrizi, K.; Minge, M.; Skjaeveland, A.; Nikolaev, S.I.; Jakobsen, K.S.; Pawlowski, J. (2007). Butler, Geraldine (ed.). 1949142. PMID 17726520.
- ^ Burki, Fabien; Shalchian-Tabrizi, Kamran; Pawlowski, Jan (August 23, 2008). 18522922.
- ^ Hallmann, Christian; Stuhr, Marleen; Kucera, Michal; et al. (2019-03-04). "Putative sponge biomarkers in unicellular Rhizaria question an early rise of animals". Nature Ecology & Evolution. 3 (4): 577–581. Bibcode:71148672.
- ^ Bass, D.; Chao, E.E.; Nikolaev, S.; et al. (February 2009). "Phylogeny of Novel Naked Filose and Reticulose Cercozoa: Granofilosea cl. n. and Proteomyxidea Revised". Protist. 160 (1): 75–109. doi:18952499.
- ^ >Howe, Alexis T.; Bass, David; Scoble, Josephine M.; et al. (2011). "Novel Cultured Protists Identify Deep-branching Environmental DNA Clades of Cercozoa: New Genera Tremula, Micrometopion, Minimassisteria, Nudifila, Peregrinia". Protist. 162 (2): 332–372. doi:21295519.
- ^ Irwin, Nicholas A. T.; Tikhonenkov, Denis V.; Hehenberger, Elisabeth; et al. (2019-01-01). "Phylogenomics supports the monophyly of the Cercozoa". Molecular Phylogenetics and Evolution. 130: 416–423. Bibcode:52982396.
- ^ a b c Lahr DJ, Parfrey LW, Mitchell EA, Katz LA, Lara E (July 2011). 21429931.
External links
[edit]- Rhizaria at UniEuk Taxonomy Map
- Molecular Phylogeny of Amoeboid Protists - Tree of Rhizaria
- Tree of Life Eukaryota