Frithjof A.S. Sterrenburg

The Glass Menagerie: diatoms for novel applications in nanotechnology

Diatoms are unicellular, eukaryotic, photosynthetic algae that are found in aquatic environments. Diatoms have enormous ecological importance on this planet and display a diversity of patterns and structures at the nano- to millimetre scale. Diatom nanotechnology, a new interdisciplinary area, has spawned collaborations in biology, biochemistry, biotechnology, physics, chemistry, material science and engineering. We survey diatom nanotechnology since 2005, emphasizing recent advances in diatom biomineralization, biophotonics, photoluminescence, microfluidics, compustat domestication, multiscale porosity, silica sequestering of proteins, detection of trace gases, controlled drug delivery and computer design. Diatoms might become the first organisms for which the gap in our knowledge of the relationship between genotype and phenotype is closed.

Molecular phylogeny and morphology of the marine diatom Talaroneis posidoniae gen. et sp. nov. (Bacillariophyta) advocate the return of the Plagiogrammaceae to the pennate diatoms

Abstract A new genus, Talaroneis Kooistra & De Stefano, gen. nov. and a new species T. posidoniae Kooistra & De Stefano, sp. nov. are described. The elongate cells, which were found on a leaf of Posidonia oceanica, formed star-, zigzag- or ribbon-shaped colonies in culture. The distinctive character of T. posidoniae was the presence of two silica wings flanking a furrow near each apical pore field. Uniseriate, transverse striae were arranged perpendicular to the apical axis; those on one side of the valve offset with respect to those on the other side. Valve poroids were occluded by perforated rotae. These morphological characteristics placed the taxon unambiguously within the supposedly centric family Plagiogrammaceae. The taxon would be excluded from the morphologically similar araphid family Rhaphoneidaceae because it lacked apical labiate processes and a clearly defined sternum. Nonetheless, a phylogeny inferred from nuclear-encoded SSU ribosomal DNA sequences of a range of diatoms unambiguously recovered T. posidoniae within the araphid pennates, close to Rhaphoneis cf. belgica (Rhaphoneidaceae). Apparently, labiate processes were lost secondarily in T. posidoniae and possibly in the common ancestor of all Plagiogrammaceae. Valve ultrastructural features of T. posidoniae would allow placement of the new species in Dimeregrammopsis but this genus was invalidly described. We transferred the single species of this genus to T. furcigerum (Grunow) Sterrenburg, comb. nov. and designated it as the type species of Talaroneis.

Universal coordinate method for locating light-microscope specimens

A description is provided of a universally applicable method of locating specimens under the light microscope, which is precisely reproducible, regardless of the brand or type of instrument used. For this method, two conditions must be met: (1) the instrument should have a graduated mechanical stage, and (2) the procedure must be rigorously standardised, as described.

Species of Pleurosigma (Pleurosigmataceae) with lanceolate or slightly sigmoid valve outlines: analysis of type material

The type material of seven taxa of Pleurosigma W. Smith were studied, including P. atlanticum Heiden & Kolbe, P. chilense Hustedt & Krasske, P. chilensis var. patagonica Ferrario & Sar, P. indicum Simonsen, P. intermedium W. Smith, P. nubecula W. Smith and P. simonsenii Hasle. All these taxa are mainly characterized by a straight or almost straight valve outline. The fine morphology of the type specimens is studied and compared with similar taxa, and appropriate taxonomic changes are proposed. The material examined included the lectotypes of P. chilense and P. atlanticum, the holotypes of P. indicum and P. simonsenii from the Friedrich Hustedt Center for Diatom Research (BRM, Germany), the isolectotypes of P. intermedium and P. nubecula from the Van Heurck Collection (BR, Belgium), and the holotype of P. chilensis var. patagonica and material of P. simonsenii collected in Argentinian coastal waters from the Herbarium of the División Ficología (LPC, Argentina). Based on light and scanning electron microscope analyses, it was concluded that P. atlanticum, P. chilense, P. indicum, P. intermedium and P. simonsenii are valid species, P. nubecula is a heterotypic synonym of P. intermedium and P. chilensis var. patagonica must be raised to specific rank under the name P. patagonicum (Ferrario & Sar) Sterrenburg & Sar stat. nov. as it differs from P. chilense in the fine morphology of the external central raphe fissures, the valve apex and the areolae near the centre.

UV photomicrography of diatoms

An historical survey of the photographic documentation of diatoms is followed by a description of a modern technique of photomicrography in ultraviolet light. With commercially available equipment, this yields the ultimate detail obtainable with a light microscope. The technique can be especially helpful in the examination (e.g., for typification) of specimens in slides with a low refractive index mounting medium, if no original material remains for scanning electrom microscopy studies.

TYPIFICATION AND TAXONOMY OF GYROSIGMA FASCIOLA (EHRENBERG) J. W. GRIFFITH ET HENFREY

Based on typification in Ehrenbergs original material, the nomenclature and taxonomy of Gyrosigma fasciola (Ehrenberg) J.W. Griffith et Henfrey are discussed. This diatom is compared to two morphologically similar taxa, Gyrosigma sulcatum (Grunow in Cleve & Grunow) Frenguelli and Gyrosigma arcuatum (Donkin) Sterrenburg, which is here recombined on the basis of a type study. It showed that taxonomic continuity has been ensured for Ehrenbergs species for more than 150 years.

GYROSIGMA SINENSE (EHRENBERG) DESIKACHARY: TYPIFICATION AND EMENDED SPECIES DESCRIPTION

Ehrenbergs type specimen of Navicula sinensis is illustrated and discussed. The taxon was transferred to the genus Gyrosigma and assigned specific status as G. sinense in Desikachary (1988). Based on our examination of the type specimen we confirm this as correct. In particular, taxonomic studies on both the type and additional specimens from other habitats in marine localities lead us to reject the varietal status under G. balticum (Ehrenberg) Rabenhorst suggested in Cleve (1894). An emended species description is given and habitat information is added.

Pleurosigma hinzianum sp. nov. and P. frenguellianum sp. nov. (Pleurosigmataceae, Bacillariophyta) from Argentinean coastal waters, in comparison with P. amara Stidolph and P. elongatum W. Smith

Two new marine diatom species from Argentinean coastal waters, Pleurosigma hinzianum Sterrenburg, Sunesen & Sar, sp. nov. and P. frenguellianum Sunesen, Sterrenburg & Sar, sp. nov., are described. The characters permitting their identification are specified, based on comparison with type material of the morphologically similar species P. amara Stidolph and P. elongatum W. Smith in the light (LM) and scanning electron microscope (SEM). New information on the type material of P. elongatum is presented and its taxonomic concept is emended. The main criteria for separation of the species discussed here are: valve outline, path of the raphe-sternum, raphe angle and angle of intersection of the oblique striae in LM; and external central and terminal raphe fissures, internal details of the central area, external and internal apical structure, and morphology of the hymen-occluded internal pores in SEM. The occurrence of these (and probably other) species in the genus Pleurosigma in net samples is adventitious and not indicative of a true planktonic mode of life.

Pleurosigma guarreranum, sp. nov. (Pleurosigmataceae, Bacillariophyta), from the Gulf of San Matías, Argentina, and comparison with the allied species Pleurosigma exemptum and P. obesum

A new marine diatom, Pleurosigma guarreranum Sar, Sterrenburg & Sunesen, sp. nov., is described with light and electron microscopy from material collected in coastal waters of the Gulf of San Matías, Río Negro Province, Argentina. Pleurosigma guarreranum resembles P. exemptum and P. obesum from the Philippines. Isotypes of P. exemptum and P. obesum deposited in the Albert Mann Collection, National Museum of Natural History, Smithsonian Institution (US), were examined with light microscopy. The observations supported a previous suggestion to include P. obesum as a heterotypic synonym of P. exemptum, which has priority. Since there is no available unmounted original material of P. exemptum, a comparative light microscopical analysis of P. guarreranum and the type material of P. exemptum was made. Despite some similarities, there are subtle differences in morphometric data, valve outline, raphe sternum pattern, and morphology of the central area. But especially, the two species consistently differ in the angle of intersection of the oblique striae, justifying a separate taxonomic position. Pleurosigma guarreranum was also compared with another species belonging to the section Formosi, P. decorum, similar in valve outline, raphe sternum pattern and angle of intersection of the oblique striae.

STUDIES ON THE GENERA GYROSIGMA AND PLEUROSIGMA (BACILLARIOPHYCEAE). PLEUROSIGMA OBSCURUM W. SMITH REVISITED

The claim that Pleurosigma obscurum W. Smith should be assigned to the genus Gyrosigma (Reid 1998a) was based on irreproducible findings. It would require that the prime generic characters of Pleurosigma and Gyrosigma (areolar arrangement in 3 obliquely and 2 perpendicularly intersecting linear systems respectively) be abandoned. Although the two oblique systems in Pleurosigma obscurum are so fine as to be beyond resolution in the LM, EM examination of the type material and specimens from other populations unequivocally reveals a 3–system arrangement precluding assignment to Gyrosigma.