Heiloo, Netherlands
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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 | Hinz F.,Alfred Wegener Institute for Polar and Marine Research | Sterrenburg F.A.S.,Stationsweg 158 | Lavigne A.S.,National University of La Plata | And 2 more authors.
Diatom Research | Year: 2012

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. © 2012 The International Society for Diatom Research.


Sar E.A.,National University of La Plata | Sar E.A.,CONICET | Sterrenburg F.A.S.,Stationsweg 158 | Lavigne A.S.,National University of La Plata | And 2 more authors.
Boletin de la Sociedad Argentina de Botanica | Year: 2013

This study focuses on the analysis of the morphology, taxonomy and distribution of species belonging to the diatom genus Pleurosigma W. Smith found in marine coastal waters of Argentina. Net samples were collected from the surface layer of the water column at several coastal stations in Buenos Aires and Río Negro Provinces. Unprocessed and cleaned materials were examined by light and scanning electron microscopy. Species identified were Pleurosigma decorum W. Smith, P. distinguendum Hustedt, P. inflatum Shadbolt, P. inscriptura M. A. Harper, P. normanii Ralfs and P. simonsenii Hasle. Two new taxa are described. Pleurosigma patagonicum var. paucistriatum nov. var. is compared with type material of Pleurosigma patagonicum (Ferrario & Sar) Sterrenburg & Sar var. patagonicum and P. perlucidum nov. spec. is compared with P. elongatum W. Smith, P. delicatulum W. Smith, P. amara Stidolph and P. brunii H. Peragallo based on type materials and/or protologues. New observations on Pleurosigma decorum, P. distinguendum, P. inflatum, P. inscriptura and P. normanii are included and differences from related species are discussed. P. inflatum is recorded for the first time from Argentina and Pleurosigma distinguendum and P. inscriptura are recorded for first time from the South Atlantic Ocean.


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.


Sterrenburg F.A.S.,Stationsweg 158 | Hamilton P.,Canadian Museum of Nature | Williams D.,Natural History Museum in London
Diatom Research | Year: 2012

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. © 2012 The International Society for Diatom Research.


Sterrenburg F.A.S.,Stationsweg 158 | Stidolph S.R.,3 15 Gebbie Rd | Sar E.A.,National University of La Plata | Sunesen I.,National University of La Plata
Phytotaxa | Year: 2015

In continuation of an earlier paper on Pleurosigma species with an (almost) non-sigmoid valve and raphe sternum, a comparative study was made in LM and SEM of Pleurosigma subrectum and P. acus. For P. subrectum, slides and a subsample of the type material were examined. For P. acus no unmounted material permitting SEM investigation is extant; a sample containing specimens fully matching the type in LM was therefore used as epitype material for SEM. The original data on striation of P. acus are emended. No morphological differences indicating separate specific status of these two taxa were observed and P. acus is therefore here designated a heterotypic synonym of P. subrectum. From the data now available, this is a very widely distributed species. The study demonstrates the indispensable role of collections for investigations on the diversity and distribution of diatom species. © 2015 Magnolia Press.


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.


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.


Sunesen I.,National University of La Plata | Sterrenburg F.A.S.,Stationsweg 158 | Sar E.A.,National University of La Plata
European Journal of Phycology | Year: 2013

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. © 2013 © British Phycological Society.


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.

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