title: Ultrastructure and molecular phylogenetic position of Heteronema scaphurum: a eukaryovorous euglenid with a cytoproct.
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.
authors: 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.
authors: Susana A
authors: SA
authors: Breglia
authors: Naoji
authors: N
authors: Yubuki
authors: Brian S
authors: BS
authors: Leander
mesh_terms: D016000:Cluster Analysis; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004705:Endocytosis; D016822:Euglenida / Q000145:classification* / Q000302:isolation & purification / Q000502:physiology / Q000648:ultrastructure*; D005618:Fresh Water / Q000469:parasitology; D020459:Genes, rRNA; D008853:Microscopy; D008969:Molecular Sequence Data; D010802:Phylogeny; D016053:RNA, Protozoan / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D016053:RNA, Protozoan; D012337:RNA, Ribosomal, 18S