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  • molecular phylogeny  (2)
  • sediment  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 406 (1999), S. 165-174 
    ISSN: 1573-5117
    Keywords: aquatic Oligochaeta ; Lake Baikal ; abyssal zone ; sediment ; abundance ; distribution ; diversity ; deep-water fauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Baikal is unique because the water circulation carries oxygen to its deepest point (1637 m), which makes it the only freshwater lake in the world with an inhabitable abyssal area. The sampling of the abyssal of the Lake was recently made possible, allowing a study of the bathymetric and vertical distribution in the sediment of Oligochaeta. Samples were taken with a Reineck box corer and subsamples were extracted and subsequently divided into slices. Factors likely to affect oligochaete abundance with depth and in the sediment were then evaluated. Identification to the species-level allowed discussion of the possible role of the abyss of Lake Baikal in the origin of oligochaete taxa and to assess if genuine deep-water taxa exist. Abundance of Oligochaeta generally follows an exponential decline with depth. An exception was one station located near a deep hot vent. In the abyssal area, all families of Oligochaeta are concentrated near the surface of the sediment. While there are generally no Naididae below 50 m, Tubificidae, Lumbriculidae, Propappidae, Enchytraeidae and Haplotaxidae are present at all depths. Evidence suggests, for the first time, that food abundance is a limiting factor of oligochaete distribution. The possibility of a genuine deep-water oligochaete fauna in Lake Baikal cannot be excluded but the low densities and the very small sizes of animals in this environment might have caused biased samples.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5117
    Keywords: oxygen microprofiles ; sediment ; ecological segregation ; Lake Baikal ; Lake Malawi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oxygen concentration profiles have been measured, by means of with microelectrodes in sediments of Lake Baikal and Lake Malawi, along transects allowing to give a survey of two major ancient Rift lakes: Lake Baikal (Eastern Siberia) and Lake Malawi (East Africa), along depth transects in the constitutive basins of the lakes and/or of relevant depths with regard to oxygen (including including the deepest point, 1680 m, in Lake Baikal). Sediment oxygen penetration depths (SOPs) display very different patterns, depending on the lake in the two lakes. In Lake Baikal, SOPs are variable, show no significant relationship with bathymetric depth and are surprisingly deep on Akademichesky ridge (〉 50.0 mm), emphasizing the distinctive feature of this region in the lake. While the Selenga river is an important source of eutrophication, the similarity of SOP-values in the Selenga shallow with those of most other sites suggests either a dilution of organic material by allochthonous matter, or a strong south-to-north transport of particles. In Lake Malawi, available oxygen is restricted to a maximum of three millimetres of the sediment, and there is a negative relationship with bathymetric depth, as a result of a steady decline of oxygen concentration with depth through the water column. Amongst the few parameters known to affect SOPs, the oxygen consumption by the sediment seems the most significant in both lakes. SOP-values furthermore confirm differences in the trophic status of Baikal and Malawi, respectively. The importance of oxygen as a factor likely to create ecological segregation for benthic organisms is discussed. Lake Malawi offers possibilities of bathymetric segregation but no vertical segregation in the sediment. In contrast, no bathymetric segregation related to oxygen is possible in Lake Baikal, but vertical segregation in the sediment is very likely.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2015-05-08
    Description: To re-evaluate the various hypotheses on the systematic position of Parergodrilus heideri Reisinger, 1925 and Hrabeiella periglandulata Pizl & Chalupský, 1984, the sole truly terrestrial non-clitellate annelids known to date, their phylogenetic relationships were investigated using a data set of new 18S rDNA sequences of these and other five relevant annelid taxa, including an unknown species of Ctenodrilidae, as well as homologous sequences already available for 18 polychaetes, one aphanoneuran, 11 clitellates, two pogonophorans, one echiuran, one sipunculan, three molluscs and two arthropods. Two different alignments were constructed, according to an algorithmic method (Clustal W) and on the basis of a secondary structure model (DCSE), A maximum parsimony analysis was performed with arthropods as an unambiguous outgroup. With both alignments, the resulting topology confirms the validity of grouping P. heideri and Stygocapitella subterranea Knöllner, 1934 into the family Parergodrilidae. Hrabeiella periglandulata never clusters with them and its position relative to this and other polychaete families is still obscure, but a close relationship with aphanoneurans is suggested by the most parsimonious trees. All these taxa appear to be far from the Clitellata. Most relationships among polychaetes are not supported by significant bootstrap and Bremer values. These polytomies are corroborated by independent evidence and are interpreted as resulting from an ancient emergence and a rapid radiation of Polychaeta.
    Keywords: Terrestrial Polychaeta ; Parergodrilus heideri ; Stygocapitella subterranea ; Hrabeiella periglandulata ; I8S rRNA gene ; molecular phylogeny ; rapid radiation
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
    Format: application/pdf
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  • 4
    Publication Date: 2024-01-12
    Description: To re-evaluate the various hypotheses on the systematic position of Parergodrilus heideri Reisinger, 1925 and Hrabeiella periglandulata Pizl & Chalupsk\xc3\xbd, 1984, the sole truly terrestrial non-clitellate annelids known to date, their phylogenetic relationships were investigated using a data set of new 18S rDNA sequences of these and other five relevant annelid taxa, including an unknown species of Ctenodrilidae, as well as homologous sequences already available for 18 polychaetes, one aphanoneuran, 11 clitellates, two pogonophorans, one echiuran, one sipunculan, three molluscs and two arthropods. Two different alignments were constructed, according to an algorithmic method (Clustal W) and on the basis of a secondary structure model (DCSE), A maximum parsimony analysis was performed with arthropods as an unambiguous outgroup. With both alignments, the resulting topology confirms the validity of grouping P. heideri and Stygocapitella subterranea Kn\xc3\xb6llner, 1934 into the family Parergodrilidae. Hrabeiella periglandulata never clusters with them and its position relative to this and other polychaete families is still obscure, but a close relationship with aphanoneurans is suggested by the most parsimonious trees. All these taxa appear to be far from the Clitellata. Most relationships among polychaetes are not supported by significant bootstrap and Bremer values. These polytomies are corroborated by independent evidence and are interpreted as resulting from an ancient emergence and a rapid radiation of Polychaeta.
    Keywords: Terrestrial Polychaeta ; Parergodrilus heideri ; Stygocapitella subterranea ; Hrabeiella periglandulata ; I8S rRNA gene ; molecular phylogeny ; rapid radiation
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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