Morphology and Phylogeny of Naked Amoebae of the Genera Thecamoeba and Stenamoeba (Thecamoebidae; Amoebozoa) from Natural Biotopes of Ukraine

Background. The family Thecamoebidae includes the genera Thecamoeba, Sappinia, Stenamoeba, Stratorugosa, and Thecochaos, which are widely distributed in water bodies and terrestrial biotopes. Species identification of naked amoebae is impossible without a combination of morphological and genetic methods.
Material and Methods. Species were determined using modern light microscopy; genomic DNA was isolated using the guanidine isothiocyanate method, and phylogenetic analysis was performed using the MEGA 10.0 software application.
Results and Discussion. Based on morphological features and 18S rRNA gene sequences, we identified nine representatives of the genus Thecamoeba (Thecamoeba striata (OQ134483, OQ134482), Thecamoeba quadrilineata (ON398268, ON398269), Thecamoeba sphaeronucleolus, Thecamoeba verrucosa, Thecamoeba terricola, Thecamoeba similis (OL604178, OL604177), Thecamoeba orbis, Thecamoeba hilla, Thecamoeba sp. (MZ079371)) and two species of the genus Stenamoeba (Stenamoeba stenopodia (OP419588, OP375108), Stenamoeba sp.). Morphological characters are given for all species, taking into account molecular data. In the molecular cluster Discosea, Thecamoebidae is a monophyletic taxon that unites groups of amoebas from the genera Thecamoeba, Sappinia, Thecochaos, Stenamoeba. Usually, Thecamoeba and Sappinia together form a sister group to the genus Thecochaos.
Conclusions. Thecamoeba-like amoebae on the phylogenetic tree form three groups: striate (Thecamoeba striata (OQ134483, OQ134482, OR994897, OL423100) + Thecamoeba vumurta (OL423099)), rugose (Thecamoeba similis (OL604178, OL604177, PQ451966, AY294145) + Thecamoeba foliovenanda (MN544291, MN544293)), and striate (Thecamoeba astrologa (MW817155) + Thecamoeba cosmophorea (MH628647) + Thecamoeba quadrilineata (ON398269, ON398268) + Thecamoeba sp. (MZ079371)) and rugose (Thecamoeba aesculea (JN247436)) morphotypes. The group of amoebae of the genus Stenamoeba (Stenamoeba stenopodia (OP375108+OP419588), Stenamoeba sp. (PQ431550), Stenamoeba dejonckheerei (MT386405), Stenamoeba berchidia (KF547922), Stenamoeba polymorpha (KU955320)), which belong to the lingulate morphotype, have a basal position in the phylogenetic tree.