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Tikhonenkov DV, Jamy M, Borodina AS, Belyaev AO, Zagumyonnyi DG, Prokina KI, Mylnikov AP, Burki F, Karpov SA. On the origin of TSAR: morphology, diversity and phylogeny of Telonemia. Open Biol 2022; 12:210325. [PMID: 35291881 PMCID: PMC8924772 DOI: 10.1098/rsob.210325] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Telonemia is a poorly known major phylum of flagellated eukaryotes with a unique combination of morphological traits. Phylogenomics recently revealed the phylogenetic position of telonemids as sister to SAR, one of the largest groups of eukaryotes, comprising Stramenopiles, Alveolata and Rhizaria. Due to this key evolutionary position, investigations of telonemids are of critical importance for elucidating the origin and diversification of an astounding diversity of eukaryotic forms and life strategies. To date, however, only two species have been morphologically characterized from Telonemia, which do not represent this genetically very diverse group. In this study, we established cultures for six new telonemid strains, including the description of five new species and a new genus. We used these cultures to update the phylogeny of Telonemia and provide a detailed morphological and ultrastructural investigation. Our data elucidate the origin of TSAR from flagellates with complex morphology and reconstruction of the ancestral structure of stramenopiles, alveolates and rhizarians, and their main synapomorphic characters. Since telonemids are a common component of aquatic environments, the features of their feeding, behaviour and ecological preferences observed in clonal cultures and the results of global metabarcoding analysis contribute to a deeper understanding of organization of microbial food webs.
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Affiliation(s)
- Denis V. Tikhonenkov
- Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia
| | - Mahwash Jamy
- Department of Organismal Biology, Program in Systematic Biology, Uppsala University, Uppsala, Sweden
| | - Anastasia S. Borodina
- Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia,Department of Zoology and Parasitology, Voronezh State University, Voronezh, Russia
| | - Artem O. Belyaev
- Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia,Department of Zoology and Ecology, Penza State University, Penza, Russia
| | - Dmitry G. Zagumyonnyi
- Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia
| | - Kristina I. Prokina
- Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia,Ecologie Systématique Evolution, CNRS, Université Paris-Saclay, AgroParisTech, Orsay, France
| | - Alexander P. Mylnikov
- Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia
| | - Fabien Burki
- Department of Organismal Biology, Program in Systematic Biology, Uppsala University, Uppsala, Sweden,Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Sergey A. Karpov
- Zoological Institute, Russian Academy of Sciences, Saint Petersburg, Russia,Department of Invertebrate Zoology, Faculty of Biology, Saint Petersburg State University, Saint Petersburg, Russia
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Mylnikov AP, Weber F, Jürgens K, Wylezich C. Massisteria marina has a sister: Massisteria voersi sp. nov., a rare species isolated from coastal waters of the Baltic Sea. Eur J Protistol 2015; 51:299-310. [DOI: 10.1016/j.ejop.2015.05.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 05/20/2015] [Accepted: 05/20/2015] [Indexed: 11/27/2022]
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Ultrastructure of the Algivorous Amoeboflagellate Viridiraptor invadens (Glissomonadida, Cercozoa). Protist 2014; 165:605-35. [PMID: 25150610 DOI: 10.1016/j.protis.2014.07.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 06/15/2014] [Accepted: 07/05/2014] [Indexed: 11/22/2022]
Abstract
The family Viridiraptoridae represents a morphologically and ecologically distinct lineage of glissomonad flagellates (Cercozoa, Rhizaria). It currently comprises two highly specialised, algivorous genera inhabiting freshwater ecosystems, Orciraptor and Viridiraptor, for which ultrastructural data were lacking. In this study, the ultrastructure of Viridiraptor invadensHess et Melkonian, the sole described species of the viridiraptorid type genus, has been studied by transmission and scanning electron microscopy. In particular the flagellar transitional region and basal apparatus, both reconstructed from serial sections, revealed ultrastructural traits, that agree with the phylogenetic placement of the viridiraptorids within Glissomonadida: The transitional region contains a distal plate/collar complex and the basal apparatus comprises two ventral posterior roots and an anterior root, all known from other glissomonads. However, two additional small microtubular roots, two conspicuous rhizoplasts and probasal bodies present during interphase represent novel characteristics. Furthermore, an acorn/V-shaped filament system was discovered at the proximal end of the flagellar transitional region and used to establish a basal body triplet numbering system for flagellate cells of the Rhizaria. Finally, ultrastructural data on perforated algal cell walls suggest that the previously described reticulocyst of Viridiraptor represents an extrusome-derived, mesh-like coat supporting the invasion/feeding process.
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Yubuki N, Leander BS. Evolution of microtubule organizing centers across the tree of eukaryotes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:230-244. [PMID: 23398214 DOI: 10.1111/tpj.12145] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 02/04/2013] [Accepted: 02/05/2013] [Indexed: 05/28/2023]
Abstract
The architecture of eukaryotic cells is underpinned by complex arrrays of microtubules that stem from an organizing center, referred to as the MTOC. With few exceptions, MTOCs consist of two basal bodies that anchor flagellar axonemes and different configurations of microtubular roots. Variations in the structure of this cytoskeletal system, also referred to as the 'flagellar apparatus', reflect phylogenetic relationships and provide compelling evidence for inferring the overall tree of eukaryotes. However, reconstructions and subsequent comparisons of the flagellar apparatus are challenging, because these studies require sophisticated microscopy, spatial reasoning and detailed terminology. In an attempt to understand the unifying features of MTOCs and broad patterns of cytoskeletal homology across the tree of eukaryotes, we present a comprehensive overview of the eukaryotic flagellar apparatus within a modern molecular phylogenetic context. Specifically, we used the known cytoskeletal diversity within major groups of eukaryotes to infer the unifying features (ancestral states) for the flagellar apparatus in the Plantae, Opisthokonta, Amoebozoa, Stramenopiles, Alveolata, Rhizaria, Excavata, Cryptophyta, Haptophyta, Apusozoa, Breviata and Collodictyonidae. We then mapped these data onto the tree of eukaryotes in order to trace broad patterns of trait changes during the evolutionary history of the flagellar apparatus. This synthesis suggests that: (i) the most recent ancestor of all eukaryotes already had a complex flagellar apparatus, (ii) homologous traits associated with the flagellar apparatus have a punctate distribution across the tree of eukaryotes, and (iii) streamlining (trait losses) of the ancestral flagellar apparatus occurred several times independently in eukaryotes.
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Affiliation(s)
- Naoji Yubuki
- The Department of Botany, Beaty Biodiversity Research Centre and Museum, University of British Columbia, 6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada.
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Paracercomonas Kinetid Ultrastructure, Origins of the Body Plan of Cercomonadida, and Cytoskeleton Evolution in Cercozoa. Protist 2012; 163:47-75. [DOI: 10.1016/j.protis.2011.06.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 06/04/2011] [Indexed: 11/20/2022]
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Ultrastructure of Allapsa vibrans and the body plan of Glissomonadida (Cercozoa). Protist 2011; 163:165-87. [PMID: 22209009 DOI: 10.1016/j.protis.2011.10.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Accepted: 10/15/2011] [Indexed: 11/23/2022]
Abstract
Biciliate, gliding zooflagellate Cercozoa are globally the most abundant and genetically diverse predators in soil (glissomonads and cercomonads). We present the first detailed ultrastructural study of a phylogenetically well-characterized glissomonad, Allapsa vibrans. There are two ventral posterior centriolar roots as in Cercomonadida, but fewer other microtubular roots. Allapsa's centriolar roots and rhizoplast basically resemble those of the less well studied glissomonads Bodomorpha and Neoheteromita. The posterior centriole of Allapsa attaches laterally to the base of the anterior centriole and to the nucleus by striated fibrillar connectors and nests in a shallow cup-like ventrolateral depression; two broad fans of single microtubules line the cup's posterior and inner side. The anterior centriole has a dorsal two-microtubule root and probably also a singlet root. Its medium-length ciliary transition zones have a proximal hub-lattice and a prominent dense distal transverse plate/collar complex. Golgi bodies are anterior/paranuclear; isodiametric extrusomes are anterior mid-ventral. Tubulicristate mitochondria attach to the nucleus, as do prominent microbodies. We characterize the body plan of glissomonads, comparing it with other Sarcomonadea: their sister group (Pansomonadida) and the phylogenetically more distant Cercomonadida. We discuss glissomonad radiation into families Sandonidae, Proleptomonadidae, Dujardinidae, Bodomorphidae and Allapsidae, establishing Aurigamonadidae fam. n. for the amoeboflagellate pansomonad Aurigamonas.
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Lahr DJG, Parfrey LW, Mitchell EAD, Katz LA, Lara E. The chastity of amoebae: re-evaluating evidence for sex in amoeboid organisms. Proc Biol Sci 2011; 278:2081-90. [PMID: 21429931 PMCID: PMC3107637 DOI: 10.1098/rspb.2011.0289] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 03/04/2011] [Indexed: 11/12/2022] Open
Abstract
Amoebae are generally assumed to be asexual. We argue that this view is a relict of early classification schemes that lumped all amoebae together inside the 'lower' protozoa, separated from the 'higher' plants, animals and fungi. This artificial classification allowed microbial eukaryotes, including amoebae, to be dismissed as primitive, and implied that the biological rules and theories developed for macro-organisms need not apply to microbes. Eukaryotic diversity is made up of 70+ lineages, most of which are microbial. Plants, animals and fungi are nested among these microbial lineages. Thus, theories on the prevalence and maintenance of sex developed for macro-organisms should in fact apply to microbial eukaryotes, though the theories may need to be refined and generalized (e.g. to account for the variation in sexual strategies and prevalence of facultative sex in natural populations of many microbial eukaryotes). We use a revised phylogenetic framework to assess evidence for sex in several amoeboid lineages that are traditionally considered asexual, and we interpret this evidence in light of theories on the evolution of sex developed for macro-organisms. We emphasize that the limited data available for many lineages coupled with natural variation in microbial life cycles overestimate the extent of asexuality. Mapping sexuality onto the eukaryotic tree of life demonstrates that the majority of amoeboid lineages are, contrary to popular belief, anciently sexual, and that most asexual groups have probably arisen recently and independently. Additionally, several unusual genomic traits are prevalent in amoeboid lineages, including cyclic polyploidy, which may serve as alternative mechanisms to minimize the deleterious effects of asexuality.
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Affiliation(s)
- Daniel J. G. Lahr
- Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Laura Wegener Parfrey
- Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Edward A. D. Mitchell
- Laboratory of Soil Biology, Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland
| | - Laura A. Katz
- Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA
| | - Enrique Lara
- Laboratory of Soil Biology, Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland
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Yabuki A, Ishida KI. Mataza hastifera n. g., n. sp.: a possible new lineage in the Thecofilosea (Cercozoa). J Eukaryot Microbiol 2011; 58:94-102. [PMID: 21205061 DOI: 10.1111/j.1550-7408.2010.00524.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A new cercozoan flagellate Mataza hastifera n. g., n. sp. is described from a surface seawater sample collected in Tokyo Bay. Cells are 3-5 μm in diameter and have two flagella. The cells alternate between swimming and stationary states in culture. Swimming cells have a nodding motion. Phylogenetic analyses using small subunit rDNA sequences demonstrate that M. hastifera belongs to the clade comprised of only environmental sequences closely related to thecofilosean cercozoans. Ultrastructural observations reveal that M. hastifera is quite similar to members of Cryomonadida, an order in Thecofilosea, and especially to Cryothecomonas spp. The cell of M. hastifera is covered with a thin double-layered theca and possesses a cylinder-shaped extrusome, as reported from cryomonads. On the other hand, the funnel that is characteristic of cryomonads was not found in the flagellar pit of M. hastifera. Combining both morphological and molecular analyses, we conclude that M. hastifera is a new lineage in Thecofilosea and suggest that Thecofilosea may be a larger group than previously thought.
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Affiliation(s)
- Akinori Yabuki
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
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Cavalier-Smith T, Lewis R, Chao EE, Oates B, Bass D. Morphology and Phylogeny of Sainouron acronematica sp. n. and the Ultrastructural Unity of Cercozoa. Protist 2008; 159:591-620. [DOI: 10.1016/j.protis.2008.04.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Accepted: 04/27/2008] [Indexed: 11/30/2022]
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Ebriid Phylogeny and the Expansion of the Cercozoa. Protist 2006; 157:279-90. [DOI: 10.1016/j.protis.2006.03.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Accepted: 03/04/2006] [Indexed: 11/22/2022]
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11
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Karpov SA, Bass D, Mylnikov AP, Cavalier-Smith T. Molecular phylogeny of Cercomonadidae and kinetid patterns of Cercomonas and Eocercomonas gen. nov. (Cercomonadida, Cercozoa). Protist 2006; 157:125-58. [PMID: 16647880 DOI: 10.1016/j.protis.2006.01.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Accepted: 01/24/2006] [Indexed: 11/23/2022]
Abstract
Cercomonads are among the most abundant and widespread zooflagellates in soil and freshwater. We cultured 22 strains and report their complete 18S rRNA sequences and light microscopic morphology. Phylogenetic analysis of 51 Cercomonas rRNA genes shows in each previously identified major clade (A, B) two very robust, highly divergent, multi-species subclades (A1, A2; B1, B2). We studied kinetid ultrastructure of five clade A representatives by serial sections. All have two closely associated left ventral posterior microtubular roots, an anterior dorsal root, a microtubule-nucleating left anterior root, and a cone of microtubules passing to the nucleus. Anterior centrioles (=basal bodies, kinetosomes) of A1 have cartwheels; the posterior centriole does not, suggesting it is older, and implying flagellar transformation similar to other bikonts. Strain C-80 (subclade A2) differs greatly, having a dorsal posterior microtubule band, but lacking the A1-specific fibrillar striated root, nuclear extension to the centrioles, centriolar diaphragm, extrusomes; both mature centrioles lack cartwheels. For clade A2 we establish Eocercomonas gen. n., with type Eocercomonas ramosa sp. n., and for clade B1 Paracercomonas gen. n. (type Paracercomonas marina sp. n.). We establish Paracercomonas ekelundi sp. n. for culture SCCAP C1 and propose a Cercomonas longicauda neotype and Cercomonas (=Neocercomonas) jutlandica comb. n. and Paracercomonas (=Cercomonas) metabolica comb. n.
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Affiliation(s)
- Serguei A Karpov
- Department of Zoology, Herzen State Pedagogical University of Russia, Moika emb. 48, 191186 St. Petersburg, Russian Federation
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Walker G, Dacks JB, Martin Embley T. Ultrastructural Description of Breviata anathema, N. Gen., N. Sp., the Organism Previously Studied as "Mastigamoeba invertens". J Eukaryot Microbiol 2006; 53:65-78. [PMID: 16579808 DOI: 10.1111/j.1550-7408.2005.00087.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An understanding of large-scale eukaryotic evolution is beginning to crystallise, as molecular and morphological data demonstrate that eukaryotes fall into six major groups. However, there are several taxa of which the affinities are yet to be resolved, and for which there are only either molecular or morphological data. One of these is the amoeboid flagellate Mastigamoeba invertens. This organism was originally misidentified and studied as a pelobiont using molecular data. We present its first light microscopical and ultrastructural characterisation. We demonstrate that it does not show affinities to the amoebozoan pelobionts, because unlike the pelobionts, it has a double basal body and two flagellar roots, a classical Golgi stack, and a large branching double membrane-bound organelle. Phylogenetic analyses of small subunit ribosomal RNA suggest an affinity with the apusomonads, when a covariotide correction for rate heterogeneity is used. We suggest that previous molecular results have been subject to artefacts from an insufficient correction for rate heterogeneity. We propose a new name for the taxon, Breviata anathema; and the unranked, apomorphy-based name "Breviates" for Breviata and its close relatives.
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Affiliation(s)
- Giselle Walker
- Department of Zoology, The Natural History Museum, London SW7 5BD, UK.
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Walochnik J, Michel R, Aspöck H. A molecular biological approach to the phylogenetic position of the genus Hyperamoeba. J Eukaryot Microbiol 2004; 51:433-40. [PMID: 15352326 DOI: 10.1111/j.1550-7408.2004.tb00391.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In 1923 Alexeieff described a new amoebic species within a new genus and named it Hyperamoeba flagellata. This amoeba exhibits three life cycle stages, an amoeboid trophozoite, a flagellated stage, and a cyst-like the heteroloboseans, the mastigamoebae, and several slime moulds. Since then more strains have been isolated and relationships to the protostelids and cercomonads and to the myxogastrid plasmodial slime moulds have been suggested. However, up to now the classification and phylogenetic position of the hyperamoebae has remained unclear. The aim of our study was to make an approach to the phylogeny of the genus Hyperamoeba with combined morphological and molecular biological data. Since 1988 we have isolated and collected Hyperamoeba-like strains from different aquatic and terrestrial sources. The 18S rDNA-sequences of 8 new Hyperamoeba strains isolated from various habitats were analysed and a cluster analysis was performed including all other available hyperamoebae. Altogether, the results of our study corroborate the relatedness of Hyperamoeba to various slime moulds. However, the hyperamoebae do not seem to be a monophyletic group, clearly putting the validity of the genus Hyperamoeba into question.
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Affiliation(s)
- Julia Walochnik
- Dept. of Med. Parasitology, Clin. Inst. of Hygiene and Med. Microbiology, Medical University of Vienna, Kinderspitalgasse 15, A-1095 Vienna, Austria.
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Cavalier-Smith T, Chao EEY, Oates B. Molecular phylogeny of Amoebozoa and the evolutionary significance of the unikont Phalansterium. Eur J Protistol 2004. [DOI: 10.1016/j.ejop.2003.10.001] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Walker G, Silberman JD, Karpov SA, Preisfeld A, Foster P, Frolov AO, Novozhilov Y, Sogin ML. An ultrastructural and molecular study of Hyperamoeba dachnaya, n. sp., and its relationship to the mycetozoan slime moulds. Eur J Protistol 2003. [DOI: 10.1078/0932-4739-00906] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Edgcomb VP, Simpson AGB, Zettler LA, Nerad TA, Patterson DJ, Holder ME, Sogin ML. Pelobionts are degenerate protists: insights from molecules and morphology. Mol Biol Evol 2002; 19:978-82. [PMID: 12032256 DOI: 10.1093/oxfordjournals.molbev.a004157] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Walker G, Simpson AG, Edgcomb V, Sogin ML, Patterson DJ. Ultrastructural identities of Mastigamoeba punctachora, Mastigamoeba simplex and Mastigella commutans and assessment of hypotheses of relatedness of the pelobionts (Protista). Eur J Protistol 2001. [DOI: 10.1078/0932-4739-00780] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Kühn S, Lange M, Medlin LK. Phylogenetic position of Cryothecomonas inferred from nuclear-encoded small subunit ribosomal RNA. Protist 2000; 151:337-45. [PMID: 11212894 DOI: 10.1078/s1434-4610(04)70032-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The systematic position of the genus Cryothecomonas has been determined from an analysis of the nuclear-encoded small subunit ribosomal RNA gene of Cryothecomonas longipes and two strains of Cryothecomonas aestivalis. Our phylogenetic trees inferred from maximum likelihood, distance and maximum parsimony methods robustly show that the genus Cryothecomonas clusters within the phylum Cercozoa, and is related to the sarcomonad flagellate Heteromita globosa. Morphological data supporting the taxonomic placement of Cryothecomonas near the sarcomonad flagellates has been compiled from the literature. The high number of nucleotide substitutions found between two morphologically indistinguishable strains of Cryothecomonas aestivalis suggests the possibility of cryptic species within Cryothecomonas aestivalis.
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Affiliation(s)
- S Kühn
- University of Bremen, Marine Botany, Bremen, Germany
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Abstract
The discipline of evolutionary protistology has emerged in the past 30 yr. There is as yet no agreed view of how protists are interrelated or how they should be classified. The foundations of a stable taxonomic superstructure for the protists and other eukaryotes lie in cataloging the diversity of the major monophyletic lineages of these organisms. The use of common patterns of cell organization (ultrastructural identity) seems to provide us with the most robust hypotheses of such lineages. These lineages are placed in 71 groups without identifiable sister taxa. These groups are here referred to as "major building blocks." For the first time, the compositions, ultrastructural identities, synapomorphies (where available), and subgroups of the major building blocks are summarized. More than 200 further lineages without clear identities are listed. This catalog includes all known major elements of the comprehensive evolutionary tree of protists and eukaryotes. Different approaches among protistologists to issues of nomenclature, ranking, and definitions of these groups are discussed, with particular reference to two groups-the stramenopiles and the Archezoa. The concept of "extended in-group" is introduced to refer to in-groups and the most proximate sister group and to assist in identifying the hierarchical location of taxa.
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Zaman V, Zaki M, Howe J, Ng M, Leipe DD, Sogin ML, Silberman JD. Hyperamoeba isolated from human feces: Description and phylogenetic affinity. Eur J Protistol 1999. [DOI: 10.1016/s0932-4739(99)80038-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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