Phylogenomics of Thecamoebida (Discosea, Amoebozoa) with the Description of Stratorugosa tubuloviscum gen. nov. sp. nov., a Freshwater Amoeba with a Perinuclear MTOC.

Thecamoebida Smirnov and Cavalier-Smith, 2011 (Discosea, Amoebozoa) has been molecularly understudied. The group until recently consisted of three genera containing species that live in terrestrial or aquatic environments. Here, we describe a fourth genus, Stratorugosa tubuloviscum gen. nov. sp. nov., which was isolated from a freshwater Amoeba proteus Ward's Science culture. Although this species most closely morphologically resembles a large, rugose Thecamoeba, S. tubuloviscum gen. nov. sp. nov. can be differentiated from Thecamoeba spp. by the following: 1) the presence of definitive finger-like (lobate-like) subpseudopodia extending at both the anterior and lateral parts of the cell during locomotion; 2) a peculiar locomotive mechanism with two sections, frontal and back, of the cells moving in a pulling and piggyback movement, respectively; 3) the presence of fibrillar cytoplasmic microtubules (MTs) organized by a prominent, perinuclear microtubule-organizing center (MTOC). A phylogenomic analysis of 511 genes assembled from transcriptomic data showed that this new genus was highly supported as sister to Stenamoeba. Despite the variance in gross morphology, Stenamoeba and S. tubuloviscum gen nov. sp. nov. both have MTOCs unlike two Thecamoeba spp., which display dot-like cytoplasmic MTs and lack an MTOC.