Voici les éléments 1 - 10 sur 65
- PublicationMétadonnées seulementSSU rRNA reveals a sequential increase in shell complexity among the euglyphid testate amoebae (Rhizaria : Euglyphida)(2007)
; ;Heger, Thierry J ; ;Meisterfeld, RalfEkelund, FlemmingThe existing data on the molecular phylogeny of filose testate amoebae from order Euglyphida has revealed contradictions between traditional morphological classification and SSU rRNA phylogeny and, moreover, the position of several important genera remained unknown. We therefore carried out a study aiming to fill several important gaps and better understand the relationships among the main euglyphid testate amoebae and the evolutionary steps that led to the present diversity at a higher level. We obtained new SSU rRNA sequences from five genera and seven species. This new phylogeny obtained shows that (1) the clade formed by species of genera Assulina and Placocista branches unambiguously at the base of the subclade of Euglyphida comprising all members of the family Trinematidae and genus Euglypha, (2) family Trinematidae (Trachelocorythion, Trinema, and Corythion) branches as a sister group to genus Euglypha, (3) three newly sequenced Euglypha species (E. cf. ciliata, E. penardi, and E. compressa) form a new clade within the genus. Since our results show that Assulina and Placocista do not belong to the Euglyphidae (unless the Trinematidae are also included in this family), we propose the creation of a new family named Assulinidae. Consequently, we give a family status to the genera Euglypha and (tentatively) Scutiglypha, which become the new family Euglyphidae. The evolutionary pattern suggested by SSU rRNA phylogeny shows a clear tendency towards increasing morphological complexity of the shell characterised by changes in the symmetry (migration of the aperture to a ventral position and/or compression of the shell) and the appearance of specialised scales at the aperture (in families Trinematidae and Euglyphidae). (C) 2007 Elsevier GmbH. All rights reserved.
- PublicationMétadonnées seulementThe Revised Classification of Eukaryotes (vol 59, pg 429, 2012)(2013)
;Adl, Sina M. ;Simpson, Alastair G. B. ;Lane, Christopher E. ;Lukes, Julius ;Bass, David ;Bowser, Samuel S. ;Brown, Matthew W. ;Burki, Fabien ;Dunthorn, Micah ;Hampl, Vladimir ;Heiss, Aaron ;Hoppenrath, M. ; ;le Gall, Line ;Lynn, Denis H. ;McManus, Hilary ; ;Mozley-Stanridge, Sharon E. ;Parfrey, Laura Wegener ;Pawlowski, Jan ;Rueckert, Sonja ;Shadwick, Laura ;Schoch, Conrad L. ;Smirnov, AlexeySpiegel, Frederick W.
- PublicationMétadonnées seulementRelationships between testate amoeba communities and water quality in Lake Donghu, a large alkaline lake in Wuhan, China(2013)
; ; ; ;Gu, Yansheng ;Wang, Hongmei ;Cui, Yongde ;Zhang, XiaokeThe middle Yangtze Reach is one of the most developed regions of China. As a result, most lakes in this area have suffered from eutrophication and serious environmental pollution during recent decades. The aquatic biodiversity in the lakes of the area is thus currently under significant threat from continuous human activities. Testate amoebae (TA) are benthic (rarely planktonic) microorganisms characterized by an agglutinated or autogenous shell. Owing to their high abundance, preservation potential in lacustrine sediments, and distinct response to environmental stress, they are increasingly used as indicators for monitoring water quality and reconstructing palaeoenvironmental changes. However this approach has not yet been developed in China. This study presents an initial assessment of benthic TA assemblages in eight lakes of Lake Donghu in the region of Wuhan, China. Testate amoeba community structure was most strongly correlated to water pH. In more alkaline conditions, communities were dominated by Centropyxis aculeata, Difflugia oblonga, Pontigulasia compressa, Pon. elisa and Lesquereusia modesta. These results are consistent with previous studies and show that TA could be useful for reconstructing past water pH fluctuations in China. To achieve this, the next step will be to expand the database and build transfer function models.
- PublicationMétadonnées seulementResponse of forest soil euglyphid testate amoebae (Rhizaria: Cercozoa) to pig cadavers assessed by high-throughput sequencing(2016-3-1)
; ; ; ; ;Decomposing cadavers modify the soil environment, but the effect on soil organisms and especially on soil protists is still poorly documented. We conducted a 35-month experiment in a deciduous forest where soil samples were taken under pig cadavers, control plots and fake pigs (bags of similar volume as the pigs). We extracted total soil DNA, amplified the SSU ribosomal RNA (rRNA) gene V9 region and sequenced it by Illumina technology and analysed the data for euglyphid testate amoebae (Rhizaria: Euglyphida), a common group of protozoa known to respond to micro- environmental changes. We found 51 euglyphid operational taxonomic units (OTUs), 45 of which did not match any known sequence. Most OTUs decreased in abundance underneath cadavers between days 0 and 309, but some responded positively after a time lag. We sequenced the full-length SSU rRNA gene of two common OTUs that responded positively to cadavers; a phylogenetic analysis showed that they did not belong to any known euglyphid family. This study confirmed the existence of an unknown diversity of euglyphids and that they react to cadavers. Results suggest that metabarcoding of soil euglyphids could be used as a forensic tool to estimate the post-mortem interval (PMI) particularly for long-term (>2 months) PMI, for which no reliable tool exists.
- PublicationMétadonnées seulementHigh-throughput sequencing reveals diverse oomycete communities in oligotrophic peat bog micro-habitat(2016-4-21)
; ; ;Steciow, Mónica M. ; ;Noelia, Paredes ; ;Tomasz, OszakoOomycete diversity has been generally underestimated, despite their ecological and economic importance. Surveying unexplored natural ecosystems with up-to-date molecular diversity tools can reveal the existence of unsuspected organisms. Here, we have explored the molecular diversity of five microhabitats located in five different oligotrophic peat bogs in the Jura Mountains using a high-throughput sequencing approach (Illumina HiSeq 2500). We found a total of 34 different phylotypes distributed in all major oomycete clades, and comprising sequences affiliated to both well-known phylotypes and members of undescribed, basal clades. Parasitic species, including obligate forms were well-represented, and phylotypes related to highly damaging invasive pathogens (Aphanomyces astaci: X1100 and Saprolegnia parasitica: X1602) were retrieved. Microhabitats differed significantly in their community composition, and many phylotypes were strongly affiliated to free water habitats (pools). Our approach proved effective in screening oomycete diversity in the studied habitat, and could be applied systematically to other environments and other fungal and fungal-like groups.
- PublicationMétadonnées seulementTime to regulate microbial eukaryote nomenclature(2012)
;Lahr, Daniel J. G. ;Nomenclature of microbial eukaryotes has been historically relegated to secondary importance. This is a legacy of the traditional classification of life into the most studied multicellular forms (plants, fungi, and animals). Despite the revolution in an understanding of eukaryotic diversity and relationships that has been achieved as a result of the use of molecular techniques, the description of microbial eukaryote genera and species is more difficult today than in the past. Researchers are at liberty to choose between the botanical (in the traditional sense) and zoological codes of nomenclature, although there is no obligation to comply with either. We demonstrate that, by combining the foci of different nomenclature codes with the current knowledge of relationships, a large number of genera and species end up being regulated by two codes (Patterson's ambiregnal taxa) and, in some cases, may even be regulated by none. We briefly present historically proposed types of solutions to this problem, and propose that an elaboration of authoritative guidelines to regulate the nomenclature of microbial eukaryotes by the community of researchers is most appropriate at this time. Most importantly, we plead to the community of researchers to resolve this centuries old outstanding issue. (C) 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, , .
- PublicationMétadonnées seulementUsing DNA-barcoding for sorting out protist species complexes: A case study of the Nebela tincta-collaris-bohemica group (Amoebozoa; Arcellinida, Hyalospheniidae)(2013)
; ;Gomaa, Fatma ; ;Heger, Thierry J.Species identification by means of morphology is often problematic in protists. Nebela tincta-collaris-bohemica (Arcellinida) is a species complex of small to medium-sized (ca. 100 mu m) testate amoebae common in peat bogs and forest soils. The taxonomic validity of characters used to define species within this group is debated and causes confusion in studies of biogeography, and applications in palaeoecology. We examined the relationship between morphological and genetic diversity within this species complex by combined analyses of light microscopy imaging and Cytochrome Oxidase Subunit 1(COI) sequences obtained from the same individual amoeba cells. Our goals were (1) to clarify the taxonomy and the phylogenetic relationships within this group, and (2) to evaluate if individual genotypes corresponded to specific morphotypes and the extent of phenotypic plasticity. We show here that small variations in test morphology that have been often overlooked by traditional taxonomy correspond to distinct haplotypes. We therefore revise the taxonomy of the group. We redefine Nebela tincta (Leidy) Kosakyan et Lara and N. collaris (Ehrenberg 1848) Kosakyan et Gomaa, change N. tincta var. rotunda Penard to N. rotunda (Penard 1890), describe three new species: N. guttata n. sp. Kosakyan et Lara, N. pechorensis n. sp. Kosakyan et Mitchell, and N. aliciae n. sp. Mitchell et Lara. (C) 2012 Elsevier GmbH. All rights reserved.
- PublicationMétadonnées seulementThe chastity of amoebae: re-evaluating evidence for sex in amoeboid organisms(2011)
;Lahr, Daniel J. G. ;Parfrey, Laura Wegener ; ;Katz, Laura A.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.
- PublicationMétadonnées seulementEcology of testate amoebae in peatlands of central China and development of a transfer function for paleohydrological reconstruction(2013)
; ; ;Lamentowicz, Mariusz ;Payne, Richard J. ; ;Gu, Yansheng ;Huang, XianyuWang, HongmeiTestate amoebae are a diverse and abundant group of protozoa that constitute a large proportion of biomass in many ecosystems and probably fill important roles in ecosystem function. These microorganisms have attracted the interest of paleoecologists because the preserved shells of testate amoebae and their known hydrological preferences enable reconstruction of past hydrological change. In ombrotrophic peatlands, surface wetness reflects hydroclimate, so testate amoebae can play an important role in reconstruction of Holocene climate change. Previous studies, however, have been geographically restricted, mostly to North America and Europe. We studied the ecology of testate amoebae in peatlands from central China in relation to hydrology, pH and metal concentrations. We found that testate amoeba community structure was correlated with depth to water table (DWT) and that the hydrological preferences of species generally matched those of previous studies. We developed a weighted average DWT transfer function that enables prediction of water table depth with a cross-validated mean error of < 5 cm. Our results demonstrate the potential for using testate amoebae to reconstruct paleohydrology in China. Such studies could contribute to our understanding of Holocene climate changes in China, particularly regarding past Asian monsoon activity.
- PublicationAccès libreWe are ready for faunistic surveys of bdelloid rotifers through DNA barcoding: the example of Sphagnum bogs of the Swiss Jura Mountains
;Fontaneto, Diego ;Eckert, Ester M ;Anicic, Nikoleta ;Mitchell, Edward A. DThe identification of biological diversity through DNA barcoding and metabarcoding of the organisms living in the field has the potential to revolutionise the way biological surveys and monitoring are performed. Yet, we still do not know if the current representativeness of the reference database of DNA sequence data is sufficient to allow such approaches. Here, we show that, at least for bdelloid rotifers (Metazoa; Rotifera; Bdelloidea) in Europe, current knowledge is ripe to perform such surveys. We show the results of an exercise performed on bdelloid rotifers in Sphagnum bogs of the Swiss Jura Mountain. The results of DNA-based identifications were rather consistent with the morphology-based identifications, and the few cases of mismatch could be used as a cautionary tale to avoid potential misinterpretations of results. The mismatches were due to cases of the closest match not being genetically very close, and to the occurrence of cryptic species., La identificación de la diversidad biológica a través de DNA barcoding y metabarcoding de los organismos en el medio ambiente tiene el potencial de revolucionar la forma en que se realizan los inventarios biológicos y el monitoreo. Sin embargo, todavía no se sabe si las bases de datos genéticos de referencia a disposición hoy en día son lo suficientemente representativas como para permitir tales enfoques. Aquí, mostramos que, al menos para los rotíferos bdelloideos (Metazoa; Rotifera; Bdelloidea) de Europa, el nivel de conocimiento es suficiente para realizar tales estudios. Mostramos los resultados de un ejercicio realizado sobre rotíferos bdelloideos en turberas de Sphagnum del Jura suizo. Los resultados de las identificaciones basadas en el ADN fueron bastante consistentes con las identificaciones basadas en la morfología, y los pocos casos de desajuste podrían utilizarse como una advertencia para evitar posibles interpretaciones erróneas de los resultados. Estos desajustes se debieron a que las secuencias más cercanas seguían alejadas de los organismos realmente encontrados y a la presencia de especies crípticas.