Andrea S. Lavigne

The diatom genus Thalassiosira: species from the northern San Matias Gulf (Rio Negro, Argentina)

This study deals with the morphology, taxonomy and distribution of species belonging to the diatom genus Thalassiosira found in the marine waters along the northern coast of San Matias Gulf, Argentina. Net samples were collected from the surface layer of the water column at Punta Orengo, Las Garzas, Banco Reparo, Los Alamos, Las Grutas, Piedras Coloradas, Bajo de Oliveira and El Fuerte from April 1998 to February 2000. Untreated and cleaned diatom samples were examined by light and scanning electron microscopy. Eighteen taxa were identified. T. frenguelliopsis is reported for the first time after its original description. T. mediterranea is a new record for the southwestern Atlantic Ocean, T. mala is a new record for Argentina, and T. angulata, T. endoseriata, T. hendeyi, T. nanolineata, T. pacifica and T. proschkinae are new records for Patagonia. Descriptions, illustrations, analysis of valve morphology and distribution are provided for the species not previously studied in detail from Argentinian coastal waters. New observations on T. frenguelliopsis and comparisons with related species known to have, or suspected of having, a similar ultrastructure are also included.

Dinophysis spp. asociadas a detección de toxinas diarreicas (DSTs) en moluscos y a intoxicación diarreica en humanos (Provincia de Buenos Aires, Argentina)

During January and February 2010 lipophilic shellfish toxins were detected in two bivalve species from Villa Gesell and Mar Azul (Argentina) by the mouse bio...

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.

REVISION OF ODONTELLA ATLANTICA (FRENGUELLI) SAR COMB. ET STAT. NOV. WITH COMPARISON TO TWO RELATED SPECIES, O. RHOMBUS (EHRENB.) KÜTZ. AND O. RHOMBOIDES R. JAHN ET KUSBER

Biddulphia rhombus var. atlantica was erected by Frenguelli from waters of the South Atlantic Ocean. A revision of its syntype series was carried out with light microscopy, a lectotype was chosen and compared with the lectotype of Odontella rhomboides (= Zygoceros rhombus), and with the lectotype of Odontella rhombus (= Denticella rhombus), designated in this paper. As there is no unmounted material available in the Frenguelli Collection, a SEM study was carried out on material collected in Buenos Aires Province coastal waters, Argentina. Differences in pattern of striation and distribution of labiate processes were established as the striking features to distinguish Frenguellis taxon from the other two species. Based on the analysis of the fine structure the placement of Frenguellis var. atlantica in the genus Odontella according to the modern concept of generic limits within the biddulphioid diatoms was confirmed and the taxon raised to species rank as Odontella atlantica, comb, et stat. nov.

First record of Thalassiosira catharinensis (Bacillariophyta) from Argentinean marine coastal waters

Several ultrastructural analyses of taxa belonging to the genus Thalassiosira from Argentinean coastal waters were carried out, nevertheless, the smaller fraction of the nanoplanktonic Thalassiosira was frequently overlooked. The aim of this study is to show the morphological variation of T. catharinensis, to compare material found in marine coastal waters of Anegada Bay, Province of Buenos Aires, with the material analyzed in the protologue and allied taxa, and to record the species for the first time in Argentina, extending its distribution.

Pseudopodosira boltovskoyi sp. nov. (Pseudopodosiraceae, Bacillariophyta) from coastal waters of Argentina

Abstract: A new extant marine diatom, Pseudopodosira boltovskoyi sp. nov. (Pseudopodosiraceae, Bacillariophyta), is described with light and scanning electron microscopy from Argentinean coastal waters. Pseudopodosira boltovskoyi sp. nov. is morphologically distinct with the following combination of characters: (1) cells with numerous lenticular chloroplasts; (2) frustules commonly heterovalvate; (3) valves with concave central area generally occupied by one to several bulges, rarely without bulges; (4) oblique striae located on a horizontal, convex shelf of the valve surface; (5) valve mantle unperforated internally and with variable number of rimmed pores located below the flange externally; (6) one ring of rimoportulae irregularly spaced, not visible externally. Pseudopodosira calyciflos (Tempère & Brun) is formally designated as the generitype, and a new name Pseudopodosira jouseana nom. nov. is proposed to replace for Pseudopodosira pileiformis based on the fact that the protologue quoted the former taxon as a synonym of the latter. We compare the new species with the morphologically allied extinct species Pseudopodosira modesta, P. wittii, P. bella, P. westii, P. hyalina and P. himilis. Although most species of Pseudopodosira are extinct, P. westii, P. calyciflos and P. echinus were recorded as extant. Nevertheless, the survival of P. westii on European coastal sediments is problematic. Pseudopodosira calyciflos was only mentioned in the protologue as living in the Hawaiian Islands but is illustrated by a figure that only shows one valve. As far as we can determine, P. echinus and Pseudopodosira boltovskoyi sp. nov. are the only extant species.

Morphological, taxonomic and nomenclatural analysis of species of Odontella, Trieres and Zygoceros (Triceratiaceae, Bacillariophyta) from Anegada Bay (Province of Buenos Aires, Argentina)

While conducting surveys of marine phytoplankton from coastal waters of the Anegada Bay (Province of Buenos Aires, Argentina) we found several eupodiscoid diatoms belonging to the genus Odontella sensu lato. Raw and cleaned samples collected at Los Pocitos, Ría del Jabalí and San Blas between 2008 and 2010, were analyzed with light and scanning electron microscopy. Based on a morphological analysis, species with loculate areolae and ocellus-bearing elevations are included in the genera Trieres (T. mobiliensis and T. sinensis) and Zygoceros (Zygoceros atlanticus comb. nov.), while species with poroid or pseudoloculate areolae and ocellus-bearing elevations are provisionally included in Odontella (O. longicruris, O. obtusa and O. rostrata). Zygoceros is revisited based on analysis of type material of species previously included in Odontella (O. atlantica, O. rhomboides and O. rhombus), their description is emended, and correct names of the transferred species are established (Zygoceros atlanticus comb. nov. and Z. ehrenbergii nom. nov.). Trieres differs from Zygoceros by having a ridge between its valve surface and mantle, longer slender polar elevations, longer external rimoportula tubes, and a planktonic style life. Following transfer of taxa with loculate areolae to Trieres and Zygoceros, Odontella only includes species with poroid and pseudoloculate areolae. Further research is necessary to establish the circumscription of Odontella, thus our conclusions are provisional.