Rhizaria

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Rhizaria
Temporal range: 650 Mya [1] (Neoproterozoic) - Present
Ammonia tepida.jpg
Ammonia tepida (Foraminifera)
Scientific classification OOjs UI icon edit-ltr.svg
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.

Contents

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 filose, 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

The three main groups of Rhizaria are: [8]

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

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

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

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]

SAR Supergroup

Sexual cycle

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]

Related Research Articles

<span class="mw-page-title-main">Vampyrellidae</span> Family of single-celled organisms

The family Vampyrellidae is a subgroup of the order Vampyrellida within the supergroup Rhizaria. Based on molecular sequence data, the family currently comprises the genus Vampyrella, and maybe several other vampyrellid amoebae. The cells are naked and characterised by radiating, filose pseudopodia and an orange colouration of the main cell body.

<span class="mw-page-title-main">Radiolaria</span> Phylum of single-celled organisms

The Radiolaria, also called Radiozoa, are unicellular eukaryotes of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm. The elaborate mineral skeleton is usually made of silica. They are found as zooplankton throughout the global ocean. As zooplankton, radiolarians are primarily heterotrophic, but many have photosynthetic endosymbionts and are, therefore, considered mixotrophs. The skeletal remains of some types of radiolarians make up a large part of the cover of the ocean floor as siliceous ooze. Due to their rapid change as species and intricate skeletons, radiolarians represent an important diagnostic fossil found from the Cambrian onwards.

<span class="mw-page-title-main">Heliozoa</span> Phylum of protists with spherical bodies

Heliozoa, commonly known as sun-animalcules, are microbial eukaryotes (protists) with stiff arms (axopodia) radiating from their spherical bodies, which are responsible for their common name. The axopodia are microtubule-supported projections from the amoeboid cell body, and are variously used for capturing food, sensation, movement, and attachment. They are similar to Radiolaria, but they are distinguished from them by lacking central capsules and other complex skeletal elements, although some produce simple scales and spines. They may be found in both freshwater and marine environments.

<span class="mw-page-title-main">Heliomonadida</span> Order of single-celled organisms

The Heliomonadida are a small group of heliozoan amoeboids that are unusual in possessing flagella throughout their life cycle.

<span class="mw-page-title-main">Cercozoa</span> Group of single-celled organisms

Cercozoa 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. They were the first major eukaryotic group to be recognized mainly through molecular phylogenies. They are the natural predators of many species of bacteria. They are closely related to the phylum Retaria, comprising amoeboids that usually have complex shells, and together form a supergroup called Rhizaria.

<span class="mw-page-title-main">Phaeodarea</span> Class of protists

Phaeodarea or Phaeodaria is a group of amoeboid cercozoan organisms. They are traditionally considered radiolarians, but in molecular trees do not appear to be close relatives of the other groups, and are instead placed among the Cercozoa. They are distinguished by the structure of their central capsule and by the presence of a phaeodium, an aggregate of waste particles within the cell.

<span class="mw-page-title-main">Lobosa</span> Phylum of protozoans

Lobosa is a taxonomic group of amoebae in the phylum Amoebozoa. Most lobosans possess broad, bluntly rounded pseudopods, although one genus in the group, the recently discovered Sapocribrum, has slender and threadlike (filose) pseudopodia. In current classification schemes, Lobosa is a subphylum, composed mainly of amoebae that have lobose pseudopods but lack cilia or flagella.

<span class="mw-page-title-main">Cercomonad</span> Order of single-celled organisms

Cercomonads are small amoeboflagellates, widespread in aqueous habitats and common in soils.

<span class="mw-page-title-main">Monadofilosa</span> Group of protists

Monadofilosa is a grouping of Cercozoa. These organisms are single-celled amoeboid protists.

<span class="mw-page-title-main">Retaria</span> Phylum of single-celled organisms

Retaria is a clade within the supergroup Rhizaria containing the Foraminifera and the Radiolaria. In 2019, the Retaria were recognized as a basal Rhizaria group, as sister of the Cercozoa.

<span class="mw-page-title-main">Protist</span> Eukaryotes other than animals, plants or fungi

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 polyphyletic grouping of several independent clades that evolved from the last eukaryotic common ancestor.

<span class="mw-page-title-main">Endomyxa</span> Group of single-celled organisms

Endomyxa is a group of eukaryotic organisms in the supergroup Rhizaria. They were initially a subphylum of Cercozoa and later a subphylum of Retaria, but several analyses have proven they are a phylogenetically separate lineage, and Endomyxa is currently regarded as its own phylum.

<span class="mw-page-title-main">Thecofilosea</span> Class of single-celled organisms

Thecofilosea is a class of unicellular testate amoebae belonging to the phylum Cercozoa. They are amoeboflagellates, organisms with flagella and pseudopodia, distinguished from other cercozoa by their scale-lacking test composed of organic material. They are closely related to the Imbricatea, a group of testate amoebae with tests composed of inorganic silica scales.

<span class="mw-page-title-main">Testate amoebae</span> Group of amoebae with shells

Testate amoebae 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.

<span class="mw-page-title-main">Sarcomonadea</span> Class of flagellate protists

The sarcomonads or class Sarcomonadea are a group of amoeboid biciliate protists in the phylum Cercozoa. They are characterized by a propensity to move through gliding on their posterior cilium or through filopodia, a lack of scales or external theca, a soft cell surface without obvious cortical filamentous or membranous skeleton, two cilia without scales or hairs, tubular mitochondrial cristae, near-spherical extrusomes, and a microbody attached to the nucleus.

<span class="mw-page-title-main">Vampyrellida</span> Order of single-celled organisms

The vampyrellids, colloquially known as vampire amoebae, are a group of free-living predatory amoebae classified as part of the lineage Endomyxa. They are distinguished from other groups of amoebae by their irregular cell shape with propensity to fuse and split like plasmodial organisms, and their life cycle with a digestive cyst stage that digests the gathered food. They appear worldwide in marine, brackish, freshwater and soil habitats. They are important predators of an enormous variety of microscopic organisms, from algae to fungi and animals. They are also known as aconchulinid amoebae.

<span class="mw-page-title-main">Amoeba</span> Cellular body type

An amoeba, often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopods. Amoebae do not form a single taxonomic group; instead, they are found in every major lineage of eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals.

Cryptofilida is an order of small heterotrophic protists in the phylum Cercozoa. They are filose amoebae that lack cilia and gliding, and are instead characterized by movement through branching or unbranched granular filopodia that are appressed to the substrate during their feeding.

<span class="mw-page-title-main">Euglyphia (protist)</span> Superorder of protists

Euglyphia is a group of imbricate protists in the phylum Cercozoa. They are unicellular eukaryotes characterized by a cell body covered in large imbricate scales, and an apical aperture through which they extend either filose pseudopodia or two cilia of different sizes that are not used for gliding.

<span class="mw-page-title-main">Amoeboflagellate</span> Cellular body type

An amoeboflagellate is any eukaryotic organism capable of behaving as an amoeba and as a flagellate at some point during their life cycle. Amoeboflagellates present both pseudopodia and at least one flagellum, often simultaneously.

References

  1. 1 2 Cavalier-Smith, Thomas; Chao, Ema E .; Lewis, Rhodri (April 2018). "Multigene phylogeny and cell evolution of chromist infrakingdom Rhizaria: contrasting cell organisation of sister phyla Cercozoa and Retaria". Protoplasma. 255 (5): 1517–1574. doi:10.1007/s00709-018-1241-1. PMC   6133090 . PMID   29666938.
  2. ↑ Sina M. Adl; David Bass; Christopher E. Lane; et al. (1 January 2019). "Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes". Journal of Eukaryotic Microbiology . 66 (1): 4–119. doi:10.1111/JEU.12691. ISSN   1066-5234. PMC   6492006 . PMID   30257078. Wikidata   Q57086550.
  3. ↑ Taylor, Christopher (2004). "Rhizaria". Archived from the original on 2009-04-20.
  4. ↑ Nikolaev, Sergey I.; Berney, Cédric; Fahrni, José F.; et al. (May 2004). "The twilight of Heliozoa and rise of Rhizaria, an emerging supergroup of amoeboid eukaryotes". PNAS. 101 (21): 8066–71. doi: 10.1073/pnas.0308602101 . PMC   419558 . PMID   15148395.
  5. ↑ Gast, Rebecca J.; Caron, David A. (2001-10-01). "Photosymbiotic associations in planktonic foraminifera and radiolaria". Hydrobiologia. 461 (1): 1–7. doi:10.1023/A:1012710909023. S2CID   1387879.
  6. ↑ Brown, Matthew W.; Kolisko, Martin; Silberman, Jeffrey D.; Roger, Andrew J. (June 2012). "Aggregative Multicellularity Evolved Independently in the Eukaryotic Supergroup Rhizaria". Current Biology . 22 (12): 1123–7. Bibcode:2012CBio...22.1123B. doi: 10.1016/j.cub.2012.04.021 . PMID   22608512.
  7. ↑ Caron DA (April 2016). "Ocean science: The rise of Rhizaria". Nature. 532 (7600): 444–5. Bibcode:2016Natur.532..444C. doi:10.1038/nature17892. PMID   27096370.
  8. ↑ 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:2007MolPE..44..255M. doi:10.1016/j.ympev.2006.11.001. PMID   17174576.
  9. ↑ Cavalier-Smith, Thomas (2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". International Journal of Systematic and Evolutionary Microbiology. 52 (2): 297–354. doi:10.1099/00207713-52-2-297. PMID   11931142.
  10. ↑ 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). "Mikrocytids are a broadly distributed and divergent radiation of parasites in aquatic invertebrates" (PDF). Curr Biol. 24 (7): 807–12. Bibcode:2014CBio...24..807H. doi: 10.1016/j.cub.2014.02.033 . PMID   24656829. S2CID   17180719.
  11. ↑ Hine, P.M.; Bower, S.M.; Meyer, G.R.; Cochennec-Laureau, N.; Berthe, F.C.J. (2001). "Ultrastructure of Mikrocytos mackini, the cause of Denman Island disease in oysters Crassostrea spp. and Ostrea spp. in British Columbia, Canada". Diseases of Aquatic Organisms. 45 (3): 215–227. doi: 10.3354/dao045215 . PMID   11558731.
  12. ↑ Carpenter, William Benjamin (1861). "XLVII.-On the systematic arrangement of the Rhizopoda". Natural History Review (Dublin and London). 1 (4): 478.
  13. ↑ Burki F, Keeling PJ (February 2014). "Rhizaria". Current Biology. 24 (3): R103–7. Bibcode:2014CBio...24.R103B. doi: 10.1016/j.cub.2013.12.025 . PMID   24502779.
  14. ↑ 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.
  15. ↑ Burki, F.; Shalchian-Tabrizi, K.; Minge, M.; Skjaeveland, A.; Nikolaev, S.I.; Jakobsen, K.S.; Pawlowski, J. (2007). Butler, Geraldine (ed.). "Phylogenomics Reshuffles the Eukaryotic Supergroups". PLoS ONE . 2 (8): e790–. Bibcode:2007PLoSO...2..790B. doi: 10.1371/journal.pone.0000790 . PMC   1949142 . PMID   17726520.
  16. ↑ Burki, Fabien; Shalchian-Tabrizi, Kamran; Pawlowski, Jan (August 23, 2008). "Phylogenomics reveals a new 'megagroup' including most photosynthetic eukaryotes". Biology Letters. 4 (4): 366–9. doi:10.1098/rsbl.2008.0224. PMC   2610160 . PMID   18522922.
  17. ↑ 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:2019NatEE...3..577N. doi:10.1038/s41559-019-0806-5. PMID   30833757. S2CID   71148672.
  18. ↑ 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:10.1016/j.protis.2008.07.002. PMID   18952499.
  19. ↑ >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:10.1016/j.protis.2010.10.002. PMID   21295519.
  20. ↑ 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:2019MolPE.130..416I. doi:10.1016/j.ympev.2018.09.004. PMID   30318266. S2CID   52982396.
  21. 1 2 3 Lahr DJ, Parfrey LW, Mitchell EA, Katz LA, Lara E (July 2011). "The chastity of amoebae: re-evaluating evidence for sex in amoeboid organisms". Proc Biol Sci. 278 (1715): 2081–90. doi:10.1098/rspb.2011.0289. PMC   3107637 . PMID   21429931.
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