Morphology, taxonomy and distribution of Stephanodiscus triporus (Bacillariophyceae) and related taxa

Stephanodiscus triporus was described in 1978, based on a study from the phytoplankton of Volgograd Reservoir that used transmission electron microscopy. This species is small, diameter 3.7–10.6 µm, with 14–30 striae and 30–60 areolae in 10 µm, and differs from other Stephanodiscus species by the presence of three satellite pores in the single central fultoportula. Later a new species similar in morphology to S. triporus, was described from Iowa, USA, namely S. vestibulis. A large population of S. vestibulis was found in Lake Balaton and the species also occurs in different Hungarian and French waters. Detailed comparison of S. triporus and S. vestibulis, based on our results and literature, showed they are very similar. Therefore we reinvestigated the type material of both and compared them with the Hungarian and French specimens. Conventional and geometric morphometric analyses were carried out, also including comparisons with the morphologically closest taxon, S. minutulus. There is a continuum of variation between S. triporus and S. vestibulis (in diameter, the number and morphology of the striae, the position of the valve face fultoportula with three satellite pores, the presence of a vestibulum having more or less the same shape). Hence we suggest that they are conspecific, with S. vestibulis a later synonym of S. triporus

Phylogeny and Fatty Acid Profiles of New Pinnularia (Bacillariophyta) Species from Soils of Vietnam

We studied the morphology, ultrastructure, and phylogeny of eight soil diatom strains assigned to the Pinnularia genus. Six of these strains, identified by us as new species, are described for the first time. We provide a comprehensive comparison with related species and include ecological data. Molecular phylogeny reconstruction using 18S rDNA and rbcL affiliates the new strains with different subclades within Pinnularia, including ‘borealis’, ‘grunowii’ and ‘stomatophora’. We also studied the fatty acid profiles in connection with the emerging biotechnological value of diatoms as a source of lipids. Stearic (36.0–64.4%), palmitic (20.1–30.4%), and palmitoleic (up to 20.8%) acids were the dominant fatty acids in the algae cultured on Waris-H + Si medium. High yields of saturated and monounsaturated fatty acids position the novel Pinnularia strains as a promising feedstock for biofuel production

Achnanthidium tinea sp. nov. – a new monoraphid diatom (Bacillariophyceae) species, described on the basis of molecular and morphological approaches

A new monoraphid diatom species Achnanthidium tinea Tseplik, Kulikovskiy, Kociolek & Maltsev, sp. nov. is described from Indonesia. The species is described on the basis of molecular and morphological analyses. According to molecular data the new species belongs to the clade that includes strains of Achnanthidium minutissimum, Achnanthidium saprophilum and Achnanthidium digitatum. Morphologically, the new species differs quite significantly from other species of the same genus because of linear-elliptic valves with almost parallel sides and strongly radiate striae and a butterfly-shaped fascia on the raphe valve. The morphology and phylogeny of the new species are discussed, and thoughts on the current state of the taxonomy of the genus Achnanthidium are expressed. Our work shows the importance of using molecular data in diatom systematics and also demonstrates the need to investigate rarely studied regions of our planet

Achnanthidium gladius sp. nov. (Bacillariophyceae) – a new monoraphid diatom species from Indonesia

A new monoraphid diatom species Achnanthidium gladius sp. nov. is described from Indonesia. The description is based on molecular data (18SV4), morphological analysis and comparison with similar species. According to molecular data, Achnanthidium gladius sp. nov. is closely related to Achnanthidium minutissimum. Morphologically, the new species differs from similar species by the absence of a fascia on raphe valve, cell size, and striae density and pattern. The new species is only known from the type locality in Indonesia. Comparison with close related species is given

<i>Fragilaria shirshovii</i> sp. nov.—A New Species of Araphid Diatoms (Bacillariophyta, Fragilariophyceae) from the Gulf of Ob (Kara Sea, Arctic)

A new species, Fragilaria shirshovii sp. nov., is described on the basis of molecular and morphological investigations. Cells were isolated from the surface levels of desalinated water masses in the zone of mixing river and marine waters in the Gulf of Ob. The morphology of this species is analyzed with light microscopy (LM) and scanning electron microscopy (SEM). The valves of F. shirshovii sp. nov. are fusiform to almost linear. The frustules are linked together in the central part, forming double comb-shaped colonies. The axial area is narrow and linear, with a distinct rounded or rectangular fascia in the center. Ghost striae are present on the central area. Areolae are not discernible in LM. Apical pore fields are composed of small pores and closed papillary outgrowths. The lips of the rimoportula are well pronounced and the striae are uniseriate. Phylogenetic analysis based on partials 18S rRNA and rbcL genes infers the species F. shirshovii sp. nov. as a member of Fragilariaceae. The species most resembling F. shirshovii sp. nov. are F. crotonensis, F. pararumpens, F. bidens and F. perminuta. The differences between F. shirshovii sp. nov. and close taxa are discussed. This work is a pioneer investigation of Fragilariaceae taxa from the freshwater ecosystems of the Siberian Arctic using a combination of morphological and molecular tools

Revision of Monoraphid Diatom Genus <i>Platessa</i> with Description of <i>Platesiberia</i> gen. nov. from Ancient Lake Baikal

A new monoraphid diatom genus, Platesiberia gen. nov., is described based on a detailed morphological investigation using light and scanning electron microscopy. The genus is based upon P. rhombicolanceolata Kulikovskiy & Lange-Bertalot and includes Platessa baicalensis Kulikovskiy & Lange-Bertalot, both species previously described from ancient Lake Baikal. Platesiberia gen. nov. is characterized by having biseriate striae on the raphe valves with uniseriate striae on the rapheless valves. Morphology of striae is helpful to distinguish the genus Platesiberia from Platessa and other monoraphid genera, and we provide a comparison of the new Baikalian genus with other freshwater monoraphid groups

Figure 4 from: Tseplik ND, Maltsev YI, Glushchenko AM, Kuznetsova IV, Genkal SI, Kociolek JP, Kulikovskiy MS (2021) Achnanthidium tinea sp. nov. – a new monoraphid diatom (Bacillariophyceae) species, described on the basis of molecular and morphological approaches. PhytoKeys 174: 147-163. https://doi.org/10.3897/phytokeys.174.60337

Figure 4 Bayesian tree of Achnanthidium tinea (Tseplik, Kulikovskiy, Kociolek & Maltsev), sp. nov. (indicated in bold) constructed from a concatenated alignment of 152 partial 18S rDNA sequences of 404 characters. Values above the horizontal lines are bootstrap support from RAxML analyses (<50 are not shown); values below the horizontal lines and to the right of the slash mark are Bayesian posterior probabilities (<90 are not shown). All sequences have strain numbers (if available). Species of centric diatoms were used as an outgroup. * is 100% statistical support

Pantocsekiella, a new centric diatom genus based on morphological and genetic studies

International audiencePrevious morphological studies showed that the description of the Cyclotella genus was too general and according to new morphological criteria new genera were established based on both recent and fossil taxa (e.g. Discostella, Handmannia, Puncticulata, Tertiarius). Furthermore, previous molecular biological investigations proved that the Cyclotella genus was not monophyletic. Integrating the above mentioned knowledge the former Cyclotella genus has been split into 4 genera (Cyclotella s.s., Discostella, Tertiarius and Lindavia). Based on the position of rimoportula Lindavia genus was formed for involving the species of both the Cyclotella ocellata and C. bodanica lineages. Our morphological and molecular (genetic distance and phylogenetic analyses of rbcL and 18S rDNA sequences) investigations suggested that "Lindavia/Cyclotella ocellata group" could be raised from the Lindavia as a separate genus. Its distinctive morphological features are the followings: striae unequal in length, central area without areolae. We describe the new genus Pantocsekiella gen. nov. and we transferred several Lindavia taxa into it. We also provide an amended diagnosis for the genus Lindavia