Cymbopleuranatellia - a new species from Transbaikal area (Russia, Siberia) described on the basis of molecular and morphological investigation

The Perizonium Ultrastructure, Divided Apical Pore Fields, Various Pore Occlusions and Visible Intermissio of Cymbella (Bacillariophyceae) with Descriptions of Four New Species

The initial valves of two Cymbella species are observed under a scanning electron microscope, and the perizonium ultrastructure of Cymbella is revealed for the first time. The perizonium is composed of alternate nodes and internodes and lacks transverse perizonium bands. Four new species, Cymbella apiculatophora sp. nov., C. hunanensis sp. nov., C. juglandis sp. nov. and C. menyuanensis sp. nov., are described using light and scanning electron microscopy based on epilithon samples collected from rivers in Hunan and Qinghai Provinces, China. Cymbella menyuanensis is a typical Cymbella species that closely resembles species in the group around C. cymbiformis Agardh, the type species of the genus. Cymbella apiculatophora is similar to C. sinensis Metzeltin & Krammer, while Cymbella hunanensis is closer to the C. hustedtii Krasske group. The last species, C. juglandis, has a cymbelloid valve outline, an obscured intermissio, internal occlusions of the areolae, dorsally deflected distal raphe fissures and a divided apical pore field at each apex, and it does not appear to belong to any group. In addition, new observations on C. cf. excisiformis Krammer and C. hustedtii are reported. The current concept of the genus Cymbella does not represent a monophyletic group as shown by molecular phylogenetic analyses. However, these analyses are still at the preliminary stage and are not yet sufficient to support a complete revision of the genus. Thus, although extremely diverse ultrastructural features are observed in the six Cymbella species investigated in this paper, we prefer to keep them within Cymbella at this moment for the sake of nomenclatural stability.

Is Sellaphora the New Navicula? Cymbosellaphora (Cymbellales), a New Genus Based on Taxa Previously Assigned to Sellaphora

A new diatom genus Cymbosellaphora Kulikovskiy, Glushchenko, Genkal and Kociolek gen. nov., was described with species Cymbosellaphora vietnamensis Glushchenko, Kulikovskiy and Kociolek sp. nov. C. vietnamensis sp. nov. was described from Vietnam and characterized by the presence of morphological features such as valves with naviculoid symmetry, slight dorsiventrality, the presence of tectula as pore occlusions, uniseriate striae, and a very broad mantle. Four species were transferred to the new genus. These are C. absoluta comb. nov., C. circumborealis comb. nov., C. geisslerae comb. nov., and C. laterostrata comb. nov. Previously, these species were members of genera Navicula Bory, Sellaphora Mereschkowsky, and Naviculadicta Lange-Bertalot. The taxonomic history of these species and genera are discussed. The tectulum is known only from the cymbelloid diatoms, and our new genus is placed within the Cymbellaceae. The presence of a tectulum demonstrates that these species cannot be placed in Sellaphora, as indicated in the literature. The recent proposal to transfer a large number of species with different morphologies to the genus Sellaphora is also discussed. Additionally, we compare pore occlusions with tectula between different genera of the Cymbellaceae with naviculoid symmetry.

The Genus Pinnularia Ehrenberg (Bacillariophyta) from the Transbaikal Area (Russia, Siberia): Description of Seven New Species on the Basis of Morphology and Molecular Data with Discussion of the Phylogenetic Position of Caloneis

Seven Pinnularia species from the Transbaikal area, Russia, are described as new for science. These are P. baicalgenkalii, P. baicalflexuosa, P. microfrauenbergiana, P. pergrunowii, P. siberiosinistra, P. baicalodivergens, and P. baicalislandica. All species are described by original LM and SEM microphotographs and molecular phylogeny. We provide comparisons between the taxa and document variability in the features found in the species. The number of Pinnularia species in the Transbaikal area is the largest number of species of the genus anywhere in the world.

Molecular and Morphological Investigations of Two Giant Diatom Cymbella Species from the Transbaikal Area (Russia, Siberia) with Comments on Their Distributions

For the first time, a giant diatom species of the genus Cymbella from Lake Baikal was studied using molecular methods. Molecular and morphological investigations allowed to us to described one new species, Cymbella baicalaspera Glushchenko, Kulikovskiy and Kociolek sp. nov. This species is both morphologically similar and phylogenetically close to a second giant Cymbella species that we investigated here, identified by us as Cymbella himalaspera Jüttner and Van de Vijver in Jüttner et al. 2010. This species was first described from Nepal on the basis of a morphological investigation. Small morphological differences exist between the type population and specimens from Lake Baikal, but otherwise the two are identical. These very interesting results show that some Baikalian diatoms can be distributed more widely and are not only endemic to this ancient lake. Similarity between Cymbella baicalaspera sp. nov. and Cymbella himalaspera on the basis of both morphological features and their close phylogenetic relationships suggested by molecular data indicate they are sister species and an example of sympatric speciation. These results also suggest an early development of a species flock. This species group warrants additional research in terms of. their diversification and biogeography.