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Heiloo, Netherlands

Hobel P.,Im Fohrenwald 35 | Sterrenburg F.A.S.,Stationsweg 158
Diatom Research | Year: 2011

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. © 2011 The International Society for Diatom Research.

Gyrosigma tenuissimum (W.Sm.) J.W.Griffith & Henfr. was examined in the original material and an emended description is presented. Its protologue contains an error of taxonomic significance: in the type material, the valve and raphe sternum do not show the considerable flexure described and illustrated in Smith (1853). A comparison with Gyrosigma coelophilum N. Okamoto & Nagumo revealed that the latter, although similar in several characters, differs sufficiently in others to warrant separate specific status. Descriptions of two new taxa are given: Gyrosigma tenuissimum var. gundulae var. nov. and Gyrosigma baculum sp. nov. Both show very fine longitudinal striae at or beyond the limit of ordinary light microscopy and are practically non-sigmoid. © 2014 Magnolia Press.

Sterrenburg F.A.,Stationsweg 158 | Hinz F.,Alfred Wegener Institute for Polar and Marine Research | Hargraves P.E.,Florida Atlantic University
Phytotaxa | Year: 2015

Type slides and the last remnant of the type sample of Haslea wawrikae were examined in LM and SEM. An emended diagnosis is presented, one new finding being that the transverse bars of the basal layer on either side of the raphe are offset—the bars on the one side aligning with the areolar foramina on the other. The species is confirmed (SEM) to have a fully developed raphe and the valve structure characterising Haslea species: an internal “grate-like” basal layer and an external tegumental layer with continuous longitudinal fissures. An erroneous identification of H. wawrikae was traced in the literature and the existence of similar, but non-conspecific, species is suspected. © 2015 Magnolia Press.

Sar E.A.,National University of La Plata | Sterrenburg F.A.S.,Stationsweg 158 | Sunesen I.,National University of La Plata
European Journal of Phycology | Year: 2014

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. © 2014 British Phycological Society.

Sterrenburg F.A.S.,Stationsweg 158 | Sar E.A.,National University of La Plata | Sar E.A.,CONICET | Sunesen I.,National University of La Plata | Sunesen I.,CONICET
Boletin de la Sociedad Argentina de Botanica | Year: 2014

The type materials of Pleurosigma formosum W. Smith and P. decorum W. Smith were examined. Both species were separated hitherto by size range, valve shape and stria density based on light microscopy (LM) analysis. However, the type materials show some overlap in the size and stria density ranges, with subtle differences in the oblique stria intersection angle, which is somewhat smaller for P. decorum. Scanning electron microscopy (SEM) analysis shows that both species share several ultrastructural features such as a thick saddle-shaped central raphe nodule, very long overlapping central raphe fissures, short hook-shaped terminal raphe fissures, general morphology of the internal hymenoccluded pores crossed by a recessed bar and presence of some scattered pairs of more deeply recessed pores lacking a bar. However, the type specimens differ in the internal morphology of the hymen-occluded areolar pores, circular, crossed by a recessed bar and rimmed in P. formosum and subcircular to elliptical, crossed by a less recessed bar, not rimmed in P. decorum. The SEM findings thus support Hendey's view that P. decorum and P. formosum are separate but closely allied species.

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