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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 7052

Alexander Kudryavtsev, Detlef Bernhard, Martin Schlegel, Ema E.-Y. Chao, and Thomas Cavalier-Smith; 18S Ribosomal RNA Gene Sequences of Cochliopodium (Himatismenida) and the Phylogeny of Amoebozoa. Protist 156:215-224, 2005

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Cochliopodium is a very distinctive genus of discoid amoebae coverd by a dorsal tectum of carbohydrate microscales. Its phylogenetic position is unclear, since although sharing many features with naked "gymnamoebae", the tectum sets it apart. We sequenced 18S ribosomal RNA genes from three Cochliopodium species (minus, spiniferum and Cochliopodium sp., a new species resembling C. minutum). Phylogenetic analysis shows Cochliopodium as robustly holophyletic and within Amoebozoa, in full accord with morphological data. Cochliopodium is always one of the basal branches within Amoebozoa but its precise position is unstable. In Bayesian analysis it is sister to holophyletic Glycostylida, but distance trees mostly place it between Dermamoeba and a possibly artifactual long-branch cluster including Thecamoeba. These positions are pooly supported and basal amoebozoan branching ill-resolved, making it unclear whether Discosea (Glycostylida, Himatismenida, Dermamoebida) is holophyletic; however, Thecamoeba seems not specifically related to Dermamoeba. We also sequenced the small-subunit rRNA gene of Vannella persistens, which constantly grouped with other Vannella species, and two Hartmannella strains. Our trees suggest that Vexilliferidae, Variosea and Hartmannella are polyphyletic, confirming the existence of two very distinct Hartmannella clades: that comprising H. cantabrigiensis and another divergent species is sister to Glaeseria, whilst Hartmannella vermiformis branches more deeply.