Anaeramoebidae fam. nov., a Novel Lineage of Anaerobic Amoebae and Amoeboflagellates of Uncertain Phylogenetic Position.

We report discovery of a new lineage of anaerobic marine amoebae and amoeboflagellates, Anaeramoeba gen. nov., represented by six newly described species. The trophic form of Anaeramoeba spp. is an amoeba corresponding to the uncommon flabellate or flamellian morphotype - it is fan-shaped and produces an anterior, flattened hyaline zone and posterior hyaline projections. In contrast to other representatives of these morphotypes, cells of Anaeramoeba spp. possess acristate mitochondrion-related organelles associated with prokaryotic symbionts, and a large acentriolar centrosome. Surprisingly, two Anaeramoeba species form morphologically unique flagellates with two or four isokont, thickened flagella. Phylogenetic analyses of the SSU rRNA gene showed that Anaeramoeba spp. form a clade, which is not robustly related to any other eukaryotic lineage. We accommodate Anaeramoeba in a new family Anaeramoebidae, which we classify as Eukaryota incertae sedis.