Ultrastructure and Molecular Phylogenetic Position of Heteronema scaphurum: A Eukaryovorous Euglenid with a Cytoproct

Authors

  • Susana A. Breglia,

    1. Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Departments of Zoology and Botany, University of British Columbia, Vancouver, BC, Canada
    Current affiliation:
    1. Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada
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  • Naoji Yubuki,

    1. Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Departments of Zoology and Botany, University of British Columbia, Vancouver, BC, Canada
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  • Brian S. Leander

    Corresponding author
    • Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Departments of Zoology and Botany, University of British Columbia, Vancouver, BC, Canada
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Correspondence

B. Leander, Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Departments of Zoology and Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada

Telephone number: 604 822 2474; FAX number: 604 822 6089;

e-mail: bleander@mail.ubc.ca

Abstract

Euglenids comprise a distinct clade of flagellates with diverse modes of nutrition, including phagotrophy, osmotrophy and phototrophy. Much of the previous research on euglenids has focused on phototrophic species because of their ecological abundance and significance as indicators for the health of aquatic ecosystems. Although largely understudied, phagotrophic species probably represent the majority of euglenid diversity. Phagotrophic euglenids tend to be either bacterivorous or eukaryovorous and use an elaborate feeding apparatus for capturing prey cells. We characterized the ultrastructure and molecular phylogenetic position of Heteronema scaphurum, a eukaryovorous euglenid collected in freshwater. This species was equipped with a distinct cytoproct through which waste products were eliminated in the form of faecal pellets; a cytoproct has not been reported in any other member of the Euglenida. Heteronema scaphurum also had a novel predatory mode of feeding. The euglenid ensnared and corralled several green algal prey cells (i.e. Chlamydomonas) with hook-like flagella covered in mucous before engulfing the bundle of prey cells whole. Molecular phylogenetic analyses inferred from small subunit rDNA sequences placed this species with other eukaryovorous euglenids, which was consistent with ultrastructural features associated with the feeding apparatus, flagellar apparatus, extrusomes, and pellicle.

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