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.