Two new species of the recently described genus Stenamoeba, named S. berchidia and S. sardiniensis were isolated from a single soil sample on Sardinia, Italy. Both share morphological features characteristic to Stenamoeba and form in phylogenetic analyses together with other Stenamoeba spp. a highly supported clade within the family Thecamoebidae. The ultrastructural investigation of Stenamoeba sardiniensis revealed the presence of cytoplasmic microtubule-organizing centers (MTOCs), located close to one of several dictyosomes found inside the cell. This is the first report of cytoplasmic MTOCs among Thecamoebidae. The presence of MTOCs is now shown in five of nine orders comprising the class Discosea and potentially could be a phylogenetic marker in this group. We re-isolated Stenamoeba limacina from German soils. This strain shows a similar morphology and an almost complete SSU rDNA sequence identity with the type strain of S. limacina originating from gills of fishes, collected in Czech Republic.
Keywords: Amoebozoa; Discosea; MTOC; Morphology; Phylogeny; Ultrastructure.
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