The current article describes Navicula vanseeasp. nov., a new species of diatom from Lake Van, a highly alkaline lake in Eastern Anatolia (Türkiye). The description is based on light and scanning electron microscopy performed on two monoclonal cultures. The complete nuclear rRNA clusters and plastid genomes have been sequenced for these two strains and the complete mitogenome for one of them. The plastome of both strains shows the probable loss of a functional ycf35 gene. They also exhibit two IB4 group I introns in their rrl, each encoding for a putative LAGLIDADG homing endonuclease, with the first L1917 IB4 intron reported amongst diatoms. The Maximum Likelihood phylogeny inferred from a concatenated alignment of 18S, rbcL and psbC distinguishes N. vanseea sp. nov. from the morphologically similar species Navicula cincta and Navicula microdigitoradiata.

In this study, we describe Halamphora vantushpaensissp. nov., a newly identified diatom species found in the highly alkaline Lake Van in Eastern Turkey (Türkiye). This new species is characterized morphologically by light and scanning electron microscopy, performed on both wild and cultivated samples. Two monoclonal cultures were submitted to a genome-skimming approach, giving access to the complete sequence of their nuclear rRNA cluster of genes, mitochondrial and plastid genomes. Both strains were highly similar from the genomic point of view, with few mutations noted, although in organellar genomes some of them concerned protein coding genes and were non-silent. Also, the group II intron in the mitochondrial cox1 gene was found to display a relatively high number of polymorphisms. The plastome also distinguishes itself from other Halamphora spp. by the extension of its inverted repeat at the expense of the two single copy regions of the genome. Maximum likelihood molecular phylogeny inferred from a concatenated three genes dataset (18S, psbC and rbcL) positions this species within the K clade, which is known to contain hypersaline to freshwater species.

We provide for the first time the complete plastid and mitochondrial genomes of a monoraphid diatom: Schizostauron trachyderma. The mitogenome is 41,957 bp in size and displays two group II introns in the cox1 gene. The 187,029 bp plastid genome features the typical quadripartite architecture of diatom genomes. It contains a group II intron in the petB gene that overlaps the large single-copy and the inverted repeat region. There is also a group IB4 intron encoding a putative LAGLIDADG homing endonuclease in the rnl gene. The multigene phylogenies conducted provide more evidence of the proximity between S. trachyderma and fistula-bearing species of biraphid diatoms.

Tryblionella (Bacillariaceae) was described by Smith in 1853, and for many years, the diagnosis of this genus was questionable. Recent molecular analysis based on the rbcL gene marker suggests that Tryblionella is a polyphyletic genus with T. apiculata, T. hungarica, and T. gaoana forming a distinct group from other Tryblionella representatives. Therefore, this study aimed to clarify the diagnosis of Tryblionella as a genus. The focus of this study was a selected group of species previously categorized within Grunow's section Apiculatae, which includes the type species T. acuminata. This classification serves as a foundation for conducting morphological and molecular comparisons with taxa of Tryblionella sensu lato, which are likely to represent distinct and highly diverse genera. Our review includes a detailed examination of frustule ultrastructure and ontogeny combined with a new molecular phylogenetic analysis derived from a three‐gene concatenated dataset. The results of our research indicated that among Tryblionella, several monophyletic groups of taxa can be distinguished, including Tryblionella sensu stricto (s.s.), by three key characters: a porose valve cross‐section; longitudinal valve undulation, where the peak of the undulation is located on the proximal side of the valve; and the presence of an axial sternum with thickened and relief virgae. Tryblionella s.s. taxa share a similar girdle structure: The girdle is graded, except that the first band bears a single row of poroids in the pars exterior and a crenulate margin on the side corresponding to the distal valve mantle.

The focus of this study was to determine the mating type of Schizostauron trachyderma and examine the relationship between cell size (life cycle), lipid droplet size, and lipid content among diatoms with similar cell dimensions. To accomplish that, we have chosen monoclonal cultures of two closely related diatom species, namely S. trachyderma and S. rawaii. In a series of experiments, we successfully induced sexual reproduction within S. trachyderma strains to reconstruct the whole cell cycle involving cells of the maximum (initial cells) and minimum viable size for a given species. The mating-type and sexual reproduction stages were described and documented. A unique experimental setting involved initial cell isolation and their lipid droplet examination using flow cytometry and confocal microscopy after Nile Red staining. The results of the series of experiments indicate correlations between cell size, the number of neutral lipids per cell, and the size of lipid droplets, suggesting that cell capacity for lipid accumulation is dependent on their position in the life cycle.