Testate amoebae in Vietnam are still poorly investigated. We studied species composition of testate amoebae in 47 waterbodies of South Vietnam provinces including natural lakes, reservoirs, wetlands, rivers, and irrigation channels. A total of 109 species and subspecies belonging to 16 genera, 9 families were identified from 191 samples. Thirty-five species and subspecies were observed in Vietnam for the first time. New species Difflugia vietnamica sp. nov. is described. The most species-rich genera are Difflugia (46 taxa), Arcella (25) and Centropyxis (14). Centropyxis aculeata was the most common species (observed in 68.1% samples). Centropyxis aerophila sphagniсola, Arcella  discoides, Difflugia schurmanni and Lesquereusia modesta were characterised by a frequency of occurrence >20%. Other species were rarer. The species accumulation curve based on the entire dataset of this work was unsaturated and well fitted by equation S = 19.46N0.33. Species richness per sample in natural lakes and wetlands were significantly higher than that of rivers (p < 0.001). The result of the Spearman rank test shows weak or statistically insignificant relationships between species richness and water temperature, pH, dissolved oxygen, and electrical conductivity.

In arid environments, protist diversity is higher in soil covered by vegetation than in bare soil and is also likely to vary in line with the marked seasonal patterns; however, these patterns have not been explored in detail in arid zones. Herein, we used culture – and morphological-based approaches to describe patterns of amoeboid protist diversity in  vegetated and bare soil areas from the intertropical desert of Tehuacán, Mexico, during dry and wet seasons. Overall, 27 protist species belonging to Amoebozoa, Discoba and Rhizaria were retrieved using culture-dependent methods. Among the soil protist groups found, Discoba (principally represented by Heterolobosea) was always the most prevalent taxa. Protist diversity was different between soil with vegetation and bare soil, principally during the dry season. Moreover, the electrical conductivity and pH of the soil were correlated with the protist species during the wet season. Our results support the hypothesis that soil protist diversity patterns exhibit a seasonal variation between dry  and wet seasons. This seasonal variation likely relies on water availability, although the role of other environmental factors cannot be completely ruled out. In addition, the soils with vegetation could be a refuge for the amoeboid protists during the harsh soil conditions of dry seasons.

Species diversity of centrohelid heliozoans in different types of freshwater bodies (forest lakes, floodplain lakes, sphagnum bogs, and river) in the Middle Russian forest-steppe was studied. The morphology of cell coverings (scales and spicules) were observed using scanning and transmission electron microscopy. A total of 20 species of  centrohelid heliozoans from five families (Acanthocystidae, Pterocystidae, Raphidiophryidae, Raphidocystidae, and Choanocystidae) and six genera (Acanthocystis, Raineriophrys, Pterocystis, Raphidiophrys, Raphidocystis, and Choanocystis) as well as unidentified Centrohelea species and a Heterophrys-like organism were found. Morphological descriptions and electron micrographs are provided. The most common species were Acanthocystis nichollsi, Raphidiophrys capitata, and a Heterophrys-like organism. The highest species diversity was observed in terrace forest lakes, whereas the lowest was seen in sphagnum bogs. Four species (Acanthocystis costata, A. elenazhivotovae, A. mikrjukovii, and A. spinosa) were found for the first time since their original description. Three species (Acanthocystis spinosa, Raphidiophrys capitata, and Pterocystis pulchra) are new records for Russia. The distribution of the observed morphospecies confirms the cosmopolitanism of many centrohelids and highlights the importance of the type of water body and microbiotope in forming the species composition. The obtained data on the morphology of studied scales supplements our knowledge of the intraspecific variability of centrohelid heliozoans.