Yulia Podunay

This study, conducted in a tropical region, investigates species from the section Planae that are morphologically similar to taxa from the Mallomonas matvienkoae / M. pseudomatvienkoae species complex, using electron microscopy and molecular data. Phylogenetic analysis of two algal cultures resolved a distinct clade, separate from any known taxa, in trees based on both SSU rDNA + rbcL cpDNA and ITS1-5.8S-ITS2 rDNA datasets. Based on these results, a new species, Mallomonas bessudovae sp. nov., is described. Data from the study of cultures are supplemented by an analysis of fixed material, which showed that the species is quite widely distributed in Vietnam.

A culture belonging to the Mallomonas favosa morphotype from Vietnam has been studied. The ultrastructure of the scales and bristles was revealed using transmission and scanning electron microscopy. Comparison of cultures from Vietnam and Europe, morphologically similar to Mallomonas favosa, using SSU rDNA + rbcL cpDNA and ITS rDNA datasets showed that the tropical culture forms a separate phylogenetic lineage. Based on these data, a new cryptic species, Mallomonas neofavosa sp. nov., is described.

This study, conducted in a tropical region, investigates species from the section Papillosae that are morphologically similar to M. furtiva and M. kalinae, using electron microscopy and molecular data. Phylogenetic analysis of three algal cultures resolved a distinct clade, separate from M. furtiva and M. kalinae, in trees based on both SSU rDNA + rbcL cpDNA and ITS1-5.8S-ITS2 rDNA datasets. Based on these results, a new species, Mallomonas imitans sp. nov., is described. This paper discusses the morphological differences between the new species and other Mallomonas taxa within the section Papillosae. The distribution of Mallomonas imitans sp. nov. appears to be restricted, as it has been found in only three localities in Vietnam.

This study describes a new diatom species of the genus Hantzschia Grunow 1877 from the Republic of Djibouti (Northeast Africa), investigated using light and electron microscopy and molecular phylogeny. Phylogenetic analysis based on concatenated datasets of partial nuclear-encoded SSU and LSU rDNA and plastid-encoded rbcL genes placed Hantzschia djiboutiensis sp. nov. in a distinct clade within a larger group containing H. amphioxys, H. stepposa, and H. belgica. Morphological analysis of the two strains from Djibouti using light and scanning electron microscopy revealed similarities to the aforementioned species, as well as differences in valve shape and dimensions, striae and fibulae count, and areolae density. Hantzschia djiboutiensis sp. nov., together with H. amphioxys, H. stepposa, and H. belgica, represents a group of Hantzschia species in which internal central raphe endings are deflected in opposite directions. Hantzschia djiboutiensis sp. nov. was found in a single temporary water body within a desert environment.

The genus Jaagichlorella Reisigl (Watanabeales, Trebouxiophyceae) was described in 1964 and revised in 2019. It includes unicellular coccoid green algae. Currently, the genus encompasses ten species and two varieties. The species from this genus inhabit different environments: freshwater, marine and as epiphytes of different natural and artificial substrates. Here, we describe Jaagichlorella terrestris sp. nov. isolated from soil biofilm from tropical forest in Cát Tiên National Park (Vietnam). A polyphasic approach combining morphological analysis, phylogenetic reconstruction, genetic distance evaluation, and CBC species concept was used to investigate the strains of new species. J. terrestris is related to J. sphaerica, but has smaller cells and some molecular differences, including the presence of CBC and hemi-CBCs.

This research is devoted to the study of Mallomonas species from the section Multisetigerae in a tropical region (Vietnam and the Philippines) using electron microscopy and molecular studies. For the first time, molecular data and phylogenetic relationships for species within this section are presented. Analysis of six algal cultures, based on a combined dataset of SSU rDNA and rbc L genes, as well as the ITS1–5.8S–ITS2 rDNA region, revealed three distinct clades. Notably, these clades did not form a monophyletic grouping. Two of the studied cultures were identified as Mallomonas multisetigera , and another two as M. neoampla . For the remaining clade, we describe a new species, Mallomonas rutabuliformis sp. nov. , which combines morphological features of fossil and modern taxa. The study also synthesizes original and literature data on the distribution of the Mallomonas multisetigera morphotype.

Mallomonas guttata species complex was investigated in a tropical region using electron microscopy and molecular phylogeny. A study of six algal cultures belonging to the M. guttata morphotype revealed two main clades based on two datasets (SSU rDNA+ rbc L cpDNA, and ITS rDNA). This work establishes the phylogenetic position of M. guttata for the first time. We propose the new species, M. monilifera sp. nov. , for organisms from the second clade, which were distinguished by the presence of a rim around the pits located on the shield on their scales and showed considerable genetic distances from the M. guttata clade. Within this new species, the strains formed two subclades, for which we propose two subspecies. Scales of the new species were also found in several water bodies on Mindanao Island (Philippines).

An unknown species of the diatom genus Ulnaria was identified during the study of freshwater environments in Mongolia. Monoclonal strains of the unknown species were obtained and subjected to molecular analysis. The strains were investigated through light and scanning electron microscopy, coupled with molecular analysis of SSU rRNA and rbcL gene sequences. The features of sexual reproduction of the cultured specimens were studied, and traits previously unknown to representatives of Ulnaria were demonstrated. Based on the results of morphological comparison against similar species from the Ulnaria ulna species complex and data from the two-gene molecular analysis, a description of Ulnaria williamsii sp. nov. was provided. Analysis of the features of sexual reproduction—gametogenesis, the mating system, and gamete movement—allowed us to discuss the species dispersion and evolution within the genus Ulnaria.

Diatoms from different water objects in Djibouti with extreme salinity (0,1–41‰), temperature (32–50°C) and pH (7,6–10.1) were studied using metabarcoding. As a result, 41 operational taxonomic units (OTUs) belonging to 18 genera of diatoms were identified.