No abstract

Telonemia is a poorly known major phylum of flagellated eukaryotes with a unique combination of morphological traits. Phylogenomics recently revealed the phylogenetic position of telonemids as sister to SAR, one of the largest groups of eukaryotes, comprising Stramenopiles, Alveolata and Rhizaria. Due to this key evolutionary position, investigations of telonemids are of critical importance for elucidating the origin and diversification of an astounding diversity of eukaryotic forms and life strategies. To date, however, only two species have been morphologically characterized from Telonemia, which do not represent this genetically very diverse group. In this study, we established cultures for six new telonemid strains, including the description of five new species and a new genus. We used these cultures to update the phylogeny of Telonemia and provide a detailed morphological and ultrastructural investigation. Our data elucidate the origin of TSAR from flagellates with complex morphology and reconstruction of the ancestral structure of stramenopiles, alveolates and rhizarians, and their main synapomorphic characters. Since telonemids are a common component of aquatic environments, the features of their feeding, behaviour and ecological preferences observed in clonal cultures and the results of global metabarcoding analysis contribute to a deeper understanding of organization of microbial food webs.

Heterolobose amoebae are important members of marine, freshwater, and soil microbial communities, but their diversity remains under-explored. We studied the diversity of Vahlkampfiidae to improve our understanding of heterolobosean relationships and their representation in aquatic benthos. Using light and electron microscopy, and molecular phylogenies based on the SSU rRNA and ITS loci, we describe the fine morphology and evolutionary relationships of a new heterolobosean Parafumarolamoeba stagnalis n. sp. from a small pond in European Russia. Cells of P. stagnalis possess a clearly distinguishable anterior hyaline pseudopodium, eruptive movement, several thin and sometimes branched uroidal filaments, spherical cysts without pores and plugs, and mitochondria that have discoid cristae and are surrounded by cisternae of the endoplasmic reticulum. The genus Parafumarolamoeba has so far included a single species, Parafumarolamoeba alta from high-altitude soil in Tibet, which is morphologically distinct from P. stagnalis. Taxonomic description for a new Parafumarolamoeba species is therefore provided.