The colonies of Microcystis, one of the most common bloom-forming cyanobacteria worldwide, harbor a diverse community of microorganisms. Among these, naked amoebae feeding on Microcystis cells can strongly influence natural Microcystis population dynamics. In this study, we investigated the species diversity of these amoebae based on 26 Microcystis-associated amoebae (MAA) strains from eutrophied water bodies in Belgium and elsewhere in western Europe. A detailed morphological characterization in combination with 18S rDNA (SSU) phylogenies revealed the presence of no less than 10 species. Nine of these belonged to the known genera Vannella (2 species), Korotnevella (2), Copromyxa (2), Vexillifera (1), Cochliopodium (1) and the recently described Angulamoeba (1). Only two were previously described, the others were new to science. One taxon could not be assigned to a known genus and is here described as Schoutedamoeba gen. n., representing a new variosean lineage. The discovery of so many new species from only one very specific habitat (Microcystis colonies) from a rather restricted geographical area indicates that the diversity of planktonic naked amoebae is much higher than previously appreciated and that only a tiny fraction of the total diversity of naked amoebae is currently known.

The soil ciliate Anteholosticha rectangula nov. spec. was discovered on King George Island in maritime Antarctica. Morphology and the nuclear SSU rDNA sequence were used to describe and infer the phylogenetic position of the new species. Anteholosticha rectangula is morphologically similar to A. bergeri and A. verrucosa, differing primarily by the morphology of the nuclear apparatus and dorsal kineties, respectively. The morphological features of related species are compared and discussed to confirm the validity of the new species. Molecular phylogenetic tree supports the previously reported polyphyly of the genus Anteholosticha.

Psammophaga fuegiais a new monothalamid foraminifera discovered in surface sediment samples in the Beagle Channel, South America. The species is a member of the important, globally distributed genus Psammophaga, which has the ability to ingest and store mineral particles inside the cytoplasm. Its shape is ovoid to pyriform, the size varies from 250 to 600 µm in length and from 200 to 400 µm in width. Like other Psammophaga species P. fuegia has a single aperture. It was found in multiple samples across the Beagle Channel area at water depths of 4 to 220 meters and in environments as variable as fjords, the main channel, and the harbour of Puerto Williams (Chile). The occurrences of the new species in environmental DNA and RNA samples correspond well to its distribution inferred from the microscopic study.

We isolated and identified a freshwater amoebozoan species that belongs to the genus Flamella Schaeffer, 1926 by single cell isolation and light microscopy. Our specific strain was isolated from a water sample obtained on the cover of a swimming pool in Petal, Mississippi, USA collected during the winter of 2015. Morphologically, our isolate is a fan-shaped amoeba with a large, frontal hyaloplasm and distinctive granuloplasm. It is capable of encystment and trophozoites occasionally have two nuclei. The isolate (GFP151sc) is phylogenetically sister to but unique from the freshwater environmental flamellid clone from Borok, Yaroslavl region, Russia originally published in 2006. Here we describe and place this isolate into a new species, Flamella piscinae n. sp.