Biodiversity of autotrophic euglenids based on the group specific DNA metabarcoding approach.

This study reports a comprehensive analysis of photoautotrophic euglenids' distribution and biodiversity in 16 small water bodies of various types (including fish ponds, field ponds, rural ponds and park ponds) located in three regions of Poland: Masovia, Masuria and Pomerania during a period of three years. By employing a euglenid specific barcode marker and a curated database of V2 18S rDNA sequences it was possible to identify 97.7 % of euglenid reads at species level. A total of 152 species classified in 13 genera were identified. The number of euglenid species found in one pond varied from 40 to 102. The most common species were Euglena agilis and Euglenaria caudata, found in every analysed waterbody. The highest number of observed species belonged to Trachelomonas and Phacus. Certain species exhibited a tendency to coexist, suggesting the presence of distinct species assemblages. Among them, the most distinctive cluster was associated with water bodies located in the Masuria region, characterized also by the greatest species richness, including many very rare species: Euglenaformis chlorophoenicea, Lepocinclis autumnalis, L. marssonii, Trachelomonas eurystoma, T. manschurica, T. mucosa, T. zuberi, T. zuberi var. nepos.

Discovery of a new photosynthetic euglenoid in Poland: Euglena mazurica sp. nov. (Euglenales, Euglenaceae).

Herein we describe a new photosynthetic euglenoid species found in Poland - Euglena mazurica. A large population exists in a small, eutrophic body of water located in a pasture near Mikolajki town inside the Masurian Landscape Park (covering a part of the Masurian Lake District in Poland). The unique cell shape (corkscrew-like) discerns it well from other previously described euglenoid species with metabolic cells. The new species possesses two plate-like chloroplasts each with a pyrenoid accompanied by two paramylon caps placed on either side of it (diplopyrenoids). On the phylogenetic tree, the new species is situated within the Euglena clade. Though it is a sister branch to three clades - one representing the similar Euglena agilis, characterized by its fusiform cells and two chloroplasts with diplopyrenoids, the two species are clearly morphologically and molecularly distinct.

Challenging the Importance of Plastid Genome Structure Conservation: New Insights From Euglenophytes.

Plastids, similar to mitochondria, are organelles of endosymbiotic origin, which retained their vestigial genomes (ptDNA). Their unique architecture, commonly referred to as the quadripartite (four-part) structure, is considered to be strictly conserved; however, the bulk of our knowledge on their variability and evolutionary transformations comes from studies of the primary plastids of green algae and land plants. To broaden our perspective, we obtained seven new ptDNA sequences from freshwater species of photosynthetic euglenids-a group that obtained secondary plastids, known to have dynamically evolving genome structure, via endosymbiosis with a green alga. Our analyses have demonstrated that the evolutionary history of euglenid plastid genome structure is exceptionally convoluted, with a patchy distribution of inverted ribosomal operon (rDNA) repeats, as well as several independent acquisitions of tandemly repeated rDNA copies. Moreover, we have shown that inverted repeats in euglenid ptDNA do not share their genome-stabilizing property documented in chlorophytes. We hypothesize that the degeneration of the quadripartite structure of euglenid plastid genomes is connected to the group II intron expansion. These findings challenge the current global paradigms of plastid genome architecture evolution and underscore the often-underestimated divergence between the functionality of shared traits in primary and complex plastid organelles.

Toward the robust resolution of taxonomic ambiguity within Lepocinclis (Euglenida) based on DNA sequencing and morphology.

DNA sequences were analyzed for three groups of species from the Lepocinclis genus (L. acus-like, L. oxyuris-like, and L. tripteris-like) along with cellular morphology. Phylogenetic analyses were based on nuclear SSU rDNA, LSU rDNA, and plastid-encoded LSU rDNA. DNA sequences were obtained from species available in culture collections (L. acus SAG 1224-1a and UTEX 1316) and those isolated directly from the environment in Poland (48 isolates), resulting in 79 new sequences. The obtained phylogenetic tree of Lepocinclis included 27 taxa, five of which are presented for the first time (L. convoluta, L. gracillimoides, L. longissima, L. pseudospiroides, and L. torta) and nine taxonomically verified and described. Based on morphology, literature data, and phylogenetic analyses, the following species were distinguished: in the L. acus-like group, L. longissima and L. acus; in the L. tripteris-like group, L. pseudospiroides, L. torta, and L. tripteris; in the L. oxyuris-like group, L. gracillimoides, L. oxyuris var. oxyuris, and L. oxyuris var. helicoidea. For all verified species, diagnostic descriptions were emended, nomenclatural adjustments were made, and epitypes were designated.

Description of Flexiglena gen. nov. and new members of Discoplastis and Euglenaformis (Euglenida).

Environmental sampling in Poland and the United States and phylogenetic analyses based on 567 sequences of four genes (155 sequences of nuclear SSU rDNA, 139 of nuclear LSU rDNA, 135 of plastid-encoded SSU rDNA, and 138 of plastid-encoded LSU rDNA) resulted in description of the new genus Flexiglena, which has been erected by accommodating Euglena variabilis, and enriching the Discoplastis and Euglenaformis genera with five new species. Four of them have joined the Discoplastis genus, currently consisting of six representatives: D. adunca, D. angusta (=Euglena angusta), D. constricta (=Lepocinclis constricta), D. excavata (=E. excavata), D. gasterosteus (=E. gasterosteus), and D. spathirhyncha. One of them has enriched the Euglenaformis genus, currently represented by two species: Euf. chlorophoenicea (= E. chlorophoenicea) and Euf. proxima. For most studied species, the diagnostic descriptions have been emended and epitypes were designated. Furthermore, the emending of Discoplastis and Euglenaformis diagnoses was performed.

Taxon-rich phylogeny and taxonomy of the genus Phacus (Euglenida) based on morphological and molecular data.

Morphological and molecular features were analyzed for a species of Phacus to better understand the phylogenetic relationships among them and establish the taxonomy. Phylogenetic analyses were based on nSSU rDNA and the research resulted in 55 new sequences. The study included species available in algal collections and those isolated directly from the environment in Poland and the Czech Republic. As a result, the obtained phylogenetic tree of Phacus includes 50 species, out of which 7 are represented on a tree for the first time (Phacus anacoelus, P. anomalus, P. curvicauda, P. elegans, P. lismorensis, P. minutus and P. stokesii) and many have been taxonomically verified. For all verified species, diagnostic descriptions were amended, the naming was reordered and epitypes were designated.

Molecular and Morphological Delimitation of Species in the Group of Lepocinclis Ovum-like taxa (Euglenida).

Although Lepocinclis ovum is recognized as a cosmopolitan and common species, and Lepocinclis globulus is the type species of the genus Lepocinclis, their correct identification is nearly impossible. The reason is that over 30 morphologically similar taxa appear in the literature, but no good diagnostic features exist to distinguish amongst them. Using environmental sampling and nuclear SSU rDNA sequencing, we delimited species within the group of Lepocinclis ovum-like taxa. Morphological and molecular features were analyzed for taxa isolated from Poland and six cultured strains from algal collections. In the case of environmental sampling, DNA was obtained from a small number of cells (20-400) isolated with a micropipette without setting up laboratory cultures (52 isolates), and phylogenetic analyses were based on the variation in nSSU rDNA. Apart from L. ovum and L. globulus, 13 other species were distinguished and four taxa (Lepocinclis conica comb. nov., L. fominii comb. nov., L. gracilicauda comb. nov., and L. pseudofominii nom. nov.) had their taxonomic ranks changed. For all verified species, diagnostic descriptions were emended and epitypes designated. The only exception was L. ovum, for which the epitype was questioned and thus, a new candidate for the epitype was suggested for future adoption.