Neidium petersiveri sp. nov. (Bacillariophyceae) — description of a new diatom species with emphasis on variability of frustule morphology in a population from Lake Superior

Light and scanning electron microscopy were used to describe Neidium petersiveri sp. nov., a previously unnamed diatom found in the Canadian waters of Lake Superior. It had been reported previously as single cells of an unidentified Neidium species from four widely separated regions in North America: Michipicoten Island (Lake Superior, Ontario, Canada), Cape Cod (Massachusetts, United States), a Quebec river (Quebec, Canada), and the Back River (Nunavut, Canada). There are superficial resemblances to Neidium mirum Krasske and Neidium calvum Østrup, but there are significant differences in frustule size and shape as well as the pattern of striae on the valve face that render N. petersiveri unique. There was not a significant correlation between frustule lengths and widths in N. petersiveri, owing to a relatively small range within the width data that resulted in much higher width-to-length ratios among shorter cells than for longer cells (74 cells measured). Other significant aspects of morphologic variation include various shapes and configurations of the lacinial fissures and of the proximal raphe fissures, and the sporadic occurrence of pit-like depressions in the axial and central regions of the valves, which suggest that variations in these characters likely have limited value as discriminating characters at the species or subspecies levels.

Light-Emitting Biosilica by In Vivo Functionalization of Phaeodactylum tricornutum Diatom Microalgae with Organometallic Complexes

In vivo incorporation of a series of organometallic photoluminescent complexes in Phaeodactylum tricornutum diatom shells (frustules) is investigated as a biotechnological route to luminescent biosilica nanostructures. [Ir(ppy)2bpy]+[PF6]−, [(2,2′-bipyridine)bis(2-phenylpyridinato)iridium(III) hexafluorophosphate], [Ru(bpy)3]2+ 2[PF6]−, [tris(2,2′-bipyridine)ruthenium(II) hexafluorophosphate], AlQ3 (tris-(8-hydroxyquinoline)aluminum), and ZnQ2 (bis-8-hydroxyquinoline-zinc) are used as model complexes to explore the potentiality and generality of the investigated process. The luminescent complexes are added to the diatom culture, and the resulting luminescent silica nanostructures are isolated by an acid-oxidative treatment that removes the organic cell matter without altering both frustule morphology and photoluminescence of incorporated emitters. Results show that, except for ZnQ2, the protocol successfully leads to the incorporation of complexes into the biosilica. The spontaneous self-adhering ability of both bare and doped Phaeodactylum tricornutum cells on conductive indium tin oxide (ITO)-coated glass slides is observed, which can be exploited to generate dielectric biofilms of living microorganisms with luminescent silica shells. In general, this protocol can be envisaged as a profitable route to new functional nanostructured materials for photonics, sensing, or biomedicine via in vivo chemical modification of diatom frustules with organometallic emitters.

Morphology and geographic distribution of three Kobayasiella species (Bacillariophyta) in northeastern European Russia

Based on scanning electron microscopy, frustule morphology of the diatoms Kobayasiella subtillissima, K. parasubtillissima and K. okadae from dystrophic weakly mineralized water bodies in northeastern European Russia (the Komi Republic and the Vologda Region) was studied. The ranges of variation in valve length and width and stria density for K. subtillissima and K. parasubtillissima coincided with published data on these species and are different for K. okadae due to interpopulation variability. Taxonomic assessment of these characters was also made. New records of K. subtillissima, K. parasubtillissima and K. оkada allowed us to clarify their geographic ranges.

Taxonomy, frustular morphology and systematics of Platichthys, a new genus of canal raphe bearing diatoms within the Entomoneidaceae

Platichthys, a new genus of canal raphe bearing diatoms, is formally described following analysis of the frustule morphology using LM and EM examination. The genus type originates from a thermal spring in the temperate climate zone of Chile, and an example of the second member of this new genus is observed from a coastal lagoon on the Galápagos Islands (Isabela Island). Taken together, the morphological features of these two newly described taxa demonstrate a unique set of characteristics observed within Thalassiophysaceae, Bacillariaceae and Entomoneidaceae. Platichthys gen. nov. contains both a canal raphe and fibulae, and the compressed valve face, absence of distinct valve mantle and numerous open porous copulae found in Platichthys gen. nov. are typical of Entomoneidaceae. However, unlike species belonging to Entomoneis, the valves of the new genus do not show frustule twisting and the striae are composed of single simple areolae instead of double rows. The most characteristic feature of the new genus is raphe positioned on an elevated keel, robust tubular fibulae, the strongly developed, steep valve face and an indistinct valve mantle in a form of a narrow structureless strip. The relationships of Platichthys gen. nov. to Nitzschia subgenus Nitzschia and to other sections of Nitzschia sensu lato, Entomoneis and to Hamatusia are discussed.

New data on the frustule morphology of rare species Sichuaniella lacustris (Bacillariophyceae)

New data on the frustule morphology of a single known species of the genus Sichuaniella — S. lacustris are provided. Apical pore fields of unusual structure, resembling single multiseriate stria on the external valve surface, together with cis-type of frustule symmetry are revealed. Another interesting feature is fusion of valve and valvocopula in entire unit. Assumption is made that specific internal processes play role of linking structures, binding valves of the same frustule to each other. According to new morphological data it is postulated that the genus should be a member of the order Cymbellales.

Planothidium galaicum sp. nov. (Bacillariophyta, Achnanthidiaceae), a new diatom species from Galician coast, Spain

A new Planothidium species, Planothidium galaicum sp. nov. is described on the basis of light and electron microscopy investigations of its frustule morphology. This diatom was found in the epiphyton of Himanthalia elongata at Muxía coast (Galicia, northwest Spain). A discussion of the morphological features of this taxon and their taxonomic affinities with related species, is presented.