Amoeboid protists are among the earliest-diverging and ecologically significant protists, yet their diversity and distribution remain insufficiently documented, particularly in tropical regions such as the Philippines. This study surveyed amoeboid protists across mesophilic and geothermal habitats in Manito, Albay, using water samples collected from four sites along a thermal gradient (25 °C, 30 °C, 42 °C, and 50 °C). Species richness and composition were assessed primarily through culture enrichment in Modified Neff’s Amoeba Saline, enabling direct morphological characterization of recovered taxa. A targeted 18S rRNA metabarcoding approach was applied as supplementary molecular confirmation of culture-based identifications. Morphological examination documented 26 culturable amoeboid protists. Species richness was the highest in Balasbas Stream (25 °C; freshwater stream) and declined across geothermal environments, including Inang Maharang (42 °C; acidic geothermal outflow) and Nagaso Boiling Lake (50 °C; saline geothermal spring). The Manito mangrove ecopark (30 °C; mesophilic estuarine site) yielded comparatively fewer taxa, potentially reflecting hydrodynamic influences on amoebae recovery. However, they should be interpreted with caution given the potential effects of sampling effort and culture-based selectivity on richness estimates. The majority of cultured genera were also detected in the molecular dataset, providing independent support for morphological identifications. As the first faunistic survey of amoeboid protists in Philippine mesophilic and geothermal habitats, this study establishes baseline distributional records, grounded in morphologically verified taxa, in understudied tropical environments.
Testate amoeba assemblage patterns were examined along an elevation gradient across various terrestrial biotopes with different types of vegetation and substrates on Yakushima Island, Japan. A set of environmental variables was used in a redundancy analysis to identify, which environmental factors best predict the observed patterns in testate amoeba assemblage composition. In addition, the main gradient in assemblage composition was analyzed by means of a coherence analysis. These two approaches showed highly consistent results. The substrate types, related with local vegetation, showed a biased distribution along an elevation gradient in the island: while the soil (top soil + litter) substrate was present throughout the gradient, Sphagnum spp. and other moss substrates were mainly found at higher elevations. Sphagnum spp. was mostly restricted to wetland biotopes. In the analysis of all biotopes and substrate types, the latter acted as the main predictor of assemblage composition. A clear elevation signal was detected in diversity characteristics of assemblages from the soil substrate: species richness and the Shannon diversity index increased with elevation. Similarly, an elevation signal was found in the composition of soil assemblages. Taken together, these results show that top-climatic factors indirectly determine the composition of testate amoeba assemblages through a predominant effect of leaf litter composition, determined by differences in the dominant vegetation corresponding to vegetation zonation along the elevation gradient.
A new species of monoxenic trypanosomatids, Zelonia arctica sp. nov. (isolate S6), was described using light and electron microscopy as well as molecular phylogenetic methods. The new species was isolated from the gut of the ichneumon fly Alexeter sp. (Hymenoptera: Ichneumonoidea) in the vicinity of Sob’ railway station, the Polar Urals mountains, Russia. An axenic laboratory culture of flagellates was obtained and deposited in the bank of living cultures of the Zoological Institute of the Russian Academy of Sciences (St. Petersburg, Russia). This is the first finding of a member of the genus Zelonia in a hymenopteran host.
Pelomyxa gruberi is one of the few representatives of the genus Pelomyxa for which it has been possible to reconstruct the life cycle in some detail, which includes uninucleate and multinucleate stages. The reproduction occurs by plasmotomy; however, the type of nuclear division is unknown. We found a local population of predominantly uninucleate P. gruberi, some of them differed in the structural organization of nuclei. Pelomyxae were examined by light and fluorescence microscopy using the combined pyronin/DAPI staining. Specific changes in nuclear structure during division have been documented.
Microsporidia Vairimorpha ceranae are virulent pathogens of the European honeybee Apis mellifera. About ten studies have confirmed that RNA interference (RNAi)-based silencing of the parasite’s genes inhibits microsporidia growth. To further evaluate the RNAi effectiveness against V. ceranae and methods for enhancing it, we synthesized in vitro double-stranded RNA (dsRNA) fragments of five genes encoding microsporidian DNA replication enzymes, their chimeric variants composed of predicted small interfering RNAs (siRNAs), and the fragments of four host genes. Fragments of the parasite’s genes encoding the PTP3 and SWP8 proteins, effective against V. ceranae at low concentrations, were used as positive controls. Ten-day feeding of individually infected and individually maintained young bees with dsRNA was followed by spore counting. This demonstrated (1) increased mortality of individually housed bees, (2) more effective infection suppression at lower dsRNA concentrations, and (3) the effectiveness of siRNA-containing chimeras and a gene fragment encoding a putative host apoptosis inhibitor in reducing spore load. Unfortunately, we were unable to enhance the RNAi efficiency by mixing the V. ceranae PTP3 fragment with polyethyleneimine and chitosan polymers, and V. ceranae growth was also unaffected when hive-derived bees of different ages were fed with E. coliexpressed dsRNA, effective in young insects. Analysis of the RNAi application to control bee pathogens indicates the need to further improve the efficiency of V. ceranae inhibition by searching for new target genes, optimizing the fragment concentration in syrup, and using the most effective dsRNA or siRNA, nanoparticles and liposomes.
