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  • 1
    Electronic Resource
    Electronic Resource
    Sequence variations in the large-subunit ribosomal RNA gene of ammonia (foraminifera, protozoa) and their evolutionary implications (1996)
    Springer
    Journal of molecular evolution 43 (1996), S. 145-151 
    Details
    ISSN: 1432-1432
    Keywords: Foraminifera ; Sequence dissimilarity ; LSU rRNA gene ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An unusually high divergence was observed in the ribosomal RNA genes of a free-living population of foraminifera belonging to the genusAmmonia. The sequences of a large-subunit (LSU) rDNA expansion segment D1 and flanking regions were obtained from 20 specimens namedAmmonia sp. 1 andAmmonia sp. 2. The sequence divergence between the two species averages 14%. Within each species it ranges from 0.2% to 7.1% inAmmonia sp. 1 and from 0.7% to 2.3% inAmmonia sp. 2. We did not find two specimens having identical sequences. Moreover, in opposition to the generally acaepted view, rDNA sequence variations were also found within a single individual. The variations among several rDNA copies in a single specimen ofAmmonia may reach up to 4.9%. Most of the observed variations result from multiplication of CA or TA serial repeats occurring in two particularly variable regions. For single base changes, C-T transitions are most frequently observed. We discuss the evolution of expansion segments and their use for phylogenetic studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02337359
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  • 2
    Electronic Resource
    Electronic Resource
    Phylogeny and Rates of Molecular Evolution of Planktonic Foraminifera: SSU rDNA Sequences Compared to the Fossil Record (1997)
    Springer
    Journal of molecular evolution 45 (1997), S. 285-294 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Planktonic foraminifera — Molecular phylogenetics — Rates of substitution — Ribosomal DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Planktonic foraminifera are marine protists, whose calcareous shells form oceanic sediments and are widely used for stratigraphic and paleoenvironmental analyses. The fossil record of planktonic foraminifera is compared here to their molecular phylogeny inferred from ribosomal DNA sequences. Eighteen partial SSU rDNA sequences from species representing all modern planktonic families (Globigerinidae, Hastigerinidae, Globorotaliidae, Candeinidae) were obtained and compared to seven sequences representing the major groups of benthic foraminifera. The phylogenetic analyses indicate a polyphyletic origin for the planktonic foraminifera. The Candeinidae, the Globorotaliidae, and the clade Globigerinidae + Hastigerinidae seem to have originated independently, at different epochs in the evolution of foraminifera. Inference of their relationships, however, is limited by substitution rates of heterogeneity. Rates of SSU rDNA evolution vary from 4.0 × 10−9 substitutions/site/year in the Globigerinidae to less than 1.0 × 10−9 substitutions/site/year in the Globorotaliidae. These variations may be related to different levels of adaptation to the planktonic mode of life. A clock-like evolution is observed among the Globigerinidae, for which molecular and paleontological data are congruent. Phylogeny of the Globorotaliidae is clearly biased by rapid rates of substitution in two species (G. truncatulinoides and G. menardii). Our study reveals differences in absolute rates of evolution at all taxonomic levels in planktonic foraminifera and demonstrates their effect on phylogenetic reconstructions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006232
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  • 3
    Electronic Resource
    Electronic Resource
    First insights into the biodiversity and biogeography of the Southern Ocean deep sea (2007)
    [s.l.] : Nature Publishing Group
    Nature 447 (2007), S. 307-311 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05827
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  • 4
    Electronic Resource
    Electronic Resource
    Naked foraminiferans revealed (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 399 (1999), S. 27-27 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It is generally assumed that the first fossil appearance of a group of organisms corresponds to its evolutionary origin. But we have molecular evidence that extant members of the most abundant microfossil-forming group, the Foraminifera, include ‘naked’ amoeboid species, indicating ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/19881
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular Identification of Algal Endosymbionts in Large Miliolid Foraminifera: 2. Dinoflagellates (2001)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 48 (2001), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Large miliolid foraminifers of the subfamily Soritinae bear symbiotic dinoflagellates morphologically similar to the species of the “Symbiodinium” complex, commonly found in corals and other marine invertebrates. Soritid foraminifers are abundant in coral reefs and it has been proposed that they share their symbionts with other dinoflagellate-bearing reef dwellers. In order to test this hypothesis, we have analysed partial large subunit ribosomal DNA sequences from dinoflagellates symbionts obtained from 28 foraminiferal specimens, and compared them to the corresponding sequences of Symbiodinium-like endosymbionts from various groups of invertebrates. Phylogenetic analysis of our data shows that all soritid symbionts belong to the “Symbiodinium” species complex, within which they form seven different molecular types (Fr1–Fr7). Only one of these types (Fr1) branches within a group of invertebrate symbionts, previously described as type C. The remaining six types form sister groups to coral symbionts previously designed as types B, C, and D. Our data indicate a high genetic diversity and specificity of Symbiodinium-like symbionts in soritids. Except for type C, we have found no evidence for the transmission of symbionts between foraminifers and other symbiont-bearing invertebrates from the same localities. However, exchanges must have occurred frequently between the different species of Soritinae, as suggested by the lack of host specificity and some biogeographical patterns observed in symbiont distribution. Our data suggest that members of the subfamily Soritinae acquired their symbionts at least three times during their history, each acquisition being followed by a rapid diversification and independent radiation of symbionts within the foraminiferal hosts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2001.tb00326.x
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  • 6
    Electronic Resource
    Electronic Resource
    How many novel eukaryotic “kingdoms”? Pitfalls and limitations of environmental DNA surveys (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Over the past few years, the use of cultivation-independent techniques to detect eukaryotic diversity has proven to be a powerful approach. Based on small-subunit ribosomal RNA (SSU rRNA) gene analyses, these studies have revealed the existence of an unexpected variety of new phylotypes. Some of them do not seem to be related to any molecularly described lineage, and have been proposed to represent novel eukaryotic kingdoms. In order to critically review the evolutionary importance of this novel high-level eukaryotic diversity and to test the potential technical and analytical pitfalls and limitations of eukaryotic environmental DNA surveys (EES), we analysed 484 environmental SSU rRNA gene sequences, including 81 new sequences from sediments of the river Seymaz (Geneva, Switzerland). Based on a detailed screening of an exhaustive alignment of SSU rRNA gene sequences and the phylogenetic re-analysis of previously published sequences using Bayesian methods, our results suggest that the number of novel higher-level taxa revealed by previous EES was over-estimated. Three main sources of errors are responsible for this situation, namely (1) the presence of undetected chimeric sequences; (2) the misplacement of several fast evolving sequences; and (3) the incomplete sampling of described, but yet unsequenced eukaryotes. EES undoubtedly contribute to unravel many novel eukaryotic lineages, but there is no clear evidence for a spectacular increase of the diversity at a megaevolutionary level. After our re-analysis, we found only five candidate lineages of possible novel high-level eukaryotic taxa. To ascertain their taxonomic status, however, the organisms themselves have to be identified now.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.05202003_1_10.x
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  • 7
    Electronic Resource
    Electronic Resource
    The twilight of sun-animalcules (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Molecular sampling of the taxonomic diversity of the living world is nowadays a task of paramount importance. Heliozoa represents one of the major eukaryotic taxa, which remain significantly underrepresented in molecular databases. The term Heliozoa was coined to embrace organisms with a rounded body and stiff pseudopodia. Despite evidences from ultrastructural studies, which conclusively show the polyphyly of selected heliozoan groups, contemporary morphological systems retain Heliozoa as a monophyletic taxon. From the perspective of reconstructing the true phylogeny of Eukaryota, molecular approaches to analyse relationships within this large protist group are evidently necessary. Phylogenetic analysis of our data shows that the four heliozoan taxa branch either independently or within different eukaryotic phyla. The actinophryids (Actinosphaerium, Actinophrys) appear as a lineage of stramenopiles, while the desmothoracids (Clathrulina, Hedriocystis) branch within “core Cercozoa”. The position of both groups is strongly supported in all analyses and is congruent with ultrastructure-based taxonomic revisions. The centrohelids (Chlamydaster, Heterophrys, Pterocystis, and Raphidiophrys) do not seem to be related to any particular eukaryotic phylum, in agreement with a recent molecular study. The taxopodid Sticholonche was found to branch between Polycystinea and Acantharea, two classes of radiolarians. Results obtained in this study suggest that the heliozoan body form cannot be used as a diagnostic argument to unite Heliozoa. Instead, we discriminate between the three heliomorphic taxa of independent origin, Actinophryida, Desmothoracida and Sticholonche, and propose the novel higher rank taxon Centrohelida. The term Heliozoa should thus be used solely in historical context.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.05202003_1_63.x
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  • 8
    Electronic Resource
    Electronic Resource
    Unexpected Foraminiferal Diversity Revealed by Small-subunit rDNA Analysis of Antarctic Sediment (2004)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 51 (2004), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Studies of benthic Foraminifera typically rely on the morphological identification of dried specimens. This approach can introduce sampling bias against small, delicate, or morphologically ambiguous forms. To overcome this limitation, we extracted total DNA from sediment followed by PCR using group- and species-specific primers. Phylogenetic analyses revealed that approximately ninety percent of the PCR products represented previously undescribed sequence types that group with undersampled members of the allogromiid Foraminifera. We also used a modification of this technique to track individual species in sediment fractions too fine for normal morphological identification, and to confirm species placement of morphologically ambiguous foraminiferans. We were able to identify the DNA of several large foraminiferal species in fine fractions in a seasonally-dependent manner, indicating that in some seasons the majority of the standing stock of these species exists as gametes/juveniles. The approach outlined here represents a powerful strategy for exploring the total diversity of benthic foraminiferal communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2004.tb00542.x
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  • 9
    Electronic Resource
    Electronic Resource
    Phylogeny of lobose amoebae based on actin and small-subunit ribosomal RNA genes (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Lobose amoebae are abundant free-living protists and important pathogenic agents, yet their evolutionary history and position in the universal tree of life are poorly known. Molecular data for lobose amoebae are limited to a few species, and all phylogenetic studies published so far lacked representatives of many of their taxonomic groups. Here we analyse actin and small-subunit ribosomal RNA (SSU rRNA) gene sequences of a broad taxon sampling of naked, lobose amoebae. Our results support the existence of a monophyletic Amoebozoa clade, which comprises all lobose amoebae examined so far, as well as the amitochondriate pelobionts and entamoebids, and the slime molds. Both actin and SSU rRNA phylogenies distinguish two well-defined clades of amoebae, the “Gymnamoebia sensu stricto” and the Archamoebae (pelobionts+entamoebids), and one weakly supported and ill-resolved group comprising some naked, lobose amoebae and the Mycetozoa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.05202003_1_26.x
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  • 10
    Electronic Resource
    Electronic Resource
    A Marine Dinoflagellate, Amphidinium eilatiensis n. sp., from the Benthos of a Mariculture Sedimentation Pond in Eilat, Israel (2003)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 50 (2003), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . A species of Amphidinium bloomed in a mariculture sedimentation pond that was used to grow bivalves near the Gulf of Eilat, Israel. Its overall length averaged 13 μm, the hypocone was 11 μm, and its width was 8μm. It has a ventral ridge. The sulcus begins at the longitudinal flagellar pore and does not project forward in the apex toward the transverse flagellar pore and left margin of the cingulum. The sulcus is a very shallow groove that projects variably about a third of the body length toward the antapex. The cingulum is a deep groove as it circles the cell from the left ventral side to the dorsal side and then becomes very shallow on the right ventral side as it arches posterior toward the longitudinal flagellar pore. Using a modified method for studying dinoflagellate chromosomes in the SEM, we observed 31 chromosomes. The plastid is dorsal and peripheral with 6 ventrally projecting peripheral digital lobes that wrap around the sides of the ventral and posterior nucleus. Amphidinium eilatiensis n. sp. is morphologically closest to Amphidinium carterae and Amphidinium rhynchocephalum, but it does not have the obvious thecal plates or polygonal units described for the former species. Instead, it has a series of spicules, bumps, and ridges on its surface. It differs from A. rhynchocephalum by two morphological characters: surface morphology and gross plastid architecture.The amplified fragments of the rDNA from A. eilatiensis n. sp. isolated from 2 separate sedimentation ponds in Eilat include the 3′-end of the SSU rDNA (about 100 nt), the whole ITS region (ITS1 + 5. 8S + ITS2) and the 5′-end of the LSU rDNA (about 900 nts). The total length of the sequences ranged from 1,460 nt. (A. eilatiensis isolate #1) to 1,461 nts. (A. eilatiensis isolate #2). The latter sequences are identical, the difference in length being due to three insertions. Amphidinium eilatiensis is genetically more closely related to A. carterae than to A. klebsii, with respectively 2. 36% and 6. 93% of sequence divergence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2003.tb00270.x
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