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.

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.

Achnanthidiumgladius sp. nov. (Bacillariophyceae) - a new monoraphid diatom species from Indonesia.

A new monoraphid diatom species Achnanthidiumgladius 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, Achnanthidiumgladius sp. nov. is closely related to Achnanthidiumminutissimum. 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.