We compared type material of Epithemia argentina described by Brun, as well as other collections with type material of two purported synonymous taxa, E. debyi and E. multicostata, described by Pantocsek, based on light and scanning electron microscopy. All three taxa were transferred to the genus Rhopalodia by M & uuml;ller. R. argentina has robust costate fibulae, a large tubular canal raphe, striae in single to double rows of areolae, and volate occlusions with a single point of attachment and positioned internally. R. argentina is distinguished from R. debyi and R. multicostata by costate fibula density and shape of the valves. The latter two species are considered heterotypic synonyms of each other. The distributions of these species over time and space are discussed.

During a survey of the diatoms present in aerophilic microhabitats associated with waterfalls in Misiones province (Argentina), aimed to explore the diatom flora occurring in these particular environments, we found a diatom belonging to the genus Stauroneis which does not match to previously recorded taxa and it is therefore described here as a new species, Stauroneis alegrensis. The new species was recorded from a sample of rock scrapings in a site affected by the waterfalls' spray and documented with light and scanning electron microscopy. The new species was compared to other morphologically similar large species with pseudosepta from other regions of the world. Although sharing with the latter the main features of valve morphology, S. alegrensis can be distinguished by its unique combination of morphometric characters.

In the framework of a study of the genus Luticola Mann we collected and processed samples from different ecoregions ofArgentina, analyzed them with light microscopy (LM) and scanning electron microscopy (SEM). In aerophilous samples collected in Misiones Province, Argentina, we found colonial specimens. The aim of this work is to elucidate the identity of the colonial forms found in aerophilous samples in NE Argentina. In the present study, we describe the genus Neoluticola Simonato, Sala et Kociolek and four species: Neoluticola spinosa Simonato, Sala et Kociolek sp. nov., Neoluticola arrechensis Simonato, Sala et Kociolek sp. nov., Neoluticola alegrensis Simonato, Sala et Kociolek sp. nov., and Neoluticola salvadoriana Simonato, Sala et Kociolek. Neoluticola comprises a group of aerophilous colonial species that share with Luticola a conspicuous isolated pore in the central area, distinctly punctate striae, and marginal channels. The new genus differs from Luticola in the location of the isolated pore on the valve face/mantle junction, colonial life habit, special structures (spines or silica projections) that join cells together, very thin slit-like areolae on the valve mantle, an elevated fascia expanded side to side, internal proximal raphe ends strongly curved, and fimbriate girdle bands. We compare the species of the new genus with morphologically similar ones from Luticola and discuss the geographic distribution of Neoluticola gen. nov.

A formal cladistic analysis of the morphological features of taxa assigned to the Orthoseiraceae, including Phycavernosa, Guarreraea and species of the genus Orthoseira is developed for 35 taxa based on 16 characters along with two Melosira species and four biddulphioid species as ingroup taxa as well as Leptocylindrus danicus as the outgroup. A consensus tree of 266 843 most parsimonious topologies suggests that the Orthoseiraceae is monophyletic, and that Guarreraea plus all former species of Orthoseira represent a monophyletic group. This analysis of morphological data did not provide support for the members of the Orthoseiraceae being more closely related to melosiroid or biddulphioid diatoms. Relationships within the monophyletic orthoseiracean group are detailed. Due to the exclusion of the generitype of Orthoseira not possessing carinoportulae which are central tube processes, one of the diagnostic features of the former Orthoseiraceae, other taxon names are described and recognized herein. We recognize and describe a new order, the Liparogyrales, based on the genus Liparogyra for taxa that were previously assigned to Orthoseira. Two families, the Phycavernosaceae, comprising the genus Phycavernosa, and the Liparogyraceae, comprising Guarreraea and taxa formerly assigned to Orthoseira, are described. The genus Liparogyra is composed of three subgenera: the subgenus Liparogyra, the subgenus Porocyclia, and the subgenus Insularis which are diagnosed by synapomorphic features. Based on our analysis, the genus Stephanosira appears to lack synapomorphies. Liparogyra, Porocyclia and Stephanosira had previously been described as genera by Ehrenberg. Guarreraea and one newly proposed genus are also included in the Liparogyraceae. Several other lineages are aphyletic, due to them either being monotypic or without diagnostic features. Thus, a total of 29 species in five genera are recognized within the newly described order and two newly described families. Eighteen new combinations are proposed for the transfer of taxa from Orthoseira to other genera. Homoplasy amongst some of the character states is discussed. The diatom genus Orthoseira as typified by O. americana does not possess carinoportulae, requiring a new approach to the nomenclature and taxonomy of the group.A phylogenetic analysis of the group using morphological data was performed, demonstrating patterns of relationships of the species for this lineage.A new classification for this diatom lineage is presented.

Eunotia is a large, taxonomically complex genus globally distributed, with many endem-ics described. In tropical regions of South America many Eunotia taxa have been reported and de-scribed. In 1933 Frenguelli reported 55 different taxa of this genus from the Iber. wetland with a high rate of endemism. One of the species reported by this author with the highest number of in-fraspecific taxa was Eunotia camelus, originally described from Cayenne and whose type material was later documented by Reichardt, allowing a better understanding of this species. E. camelus has been reported worldwide in its distribution and there has been great confusion about the identity and distribution of this supposedly cosmopolitan species. The purpose of the present study is to detail with LM and SEM observations, taxa of E. camelus and its close allies reported in the Iber. wetland ecosystem by Frenguelli, and to consider the biogeographic distribution of this species complex. We analyzed samples from both recent and historical collections from different geograph-ic areas: Esteros del Iber. (Argentina), Banka Island (Indonesia) and Kolhapur, Western Ghats (India). As a result we conclude that the E. camelus complex originally reported from the Iber. in fact contains four different species: Eunotia camelus, Eunotia juga comb. nov. stat. nov., Eunotia ectorii nom. nov. stat. nov., and Eunotia carambolensis nov. spec. Furthermore, these taxa are not conspecific with those described from Indonesia and India. Our observations show that E. camelus is not a cosmopolitan or pantropical species, but it and its close allies rather comprise a group of morphologically similar species, each with a much more limited distribution.

During a survey of the diatoms present in aerophilic microhabitats associated with waterfalls in Misiones Province (Argentina), mainly within Iguazil National Park (N.P.), seventeen taxa belonging to the genus Humidophila have been recorded. Previously, only six species of the genus have been reported for all of Argentina. Of the seventeen taxa considered here, four exhibit a unique combination of features and are pro-posed as new species. These are H. iguazuensis sp. nov., H. lagartiensis sp. nov., H. misionera sp. nov. and H. sebastianii sp. nov. An additional six previously-described species (H. arcuatoides , H. contenta , H. nienta , H. parallela , H. platensis and H. subtropica) are reported. Of these previously-described taxa, only H. contenta has been reported previously from Argentina, so the occurrences of the others in the region expand their known geographic distributions. One taxon has been tentatively identified (as Humidophila aff. biscutella) and the remaining six taxa observed are presumed to be new but remain unidentified at the species level because they occurred in small numbers and could not be sufficiently documented for formal description. This is currently the largest concentration of Humidophila taxa reported in a relatively small geographic region anywhere in the world. Morphological features among the species of the genus are discussed, and we describe the structure of the features associated with longitudinal tubes in the genus. We also present and describe the ecological and biogeographic distributions of Humidophila species.

We provide a detailed history of the taxa included in the genera Orthoseira, Guarreraea and Phycocavernosa, their circumscription, taxa included in them, and current status of each taxon. The historical overview, covering over 160 years, includes the many ideas about the genus Orthoseira, from its original description by Thwaites, to other interpretations by Smith, Crawford, Spaulding and Kociolek, and Houk. Most recently, Orthoseira species have been assumed to possess the feature of carinoportulae, which are centrally-placed pores differentiated in size and structure from areolae. The challenges presented by the generitype of Orthoseira, O. americana are discussed, since its original illustration did not indicate the presence of carinoportulae and original material of this diatom is apparently lost. The following recommendations are made in light of the current situation: 1) That the genus name Orthoseira be reserved only for O. americana, the species described as Melosira americana by Kutzing from South America, since this species was never illustrated with carinoportulae. 2) Further revision of taxa previously assigned to Orthoseira, as well as taxa shown to possess carinoportulae but assigned to other genera, as well as descriptions of new taxa, are encouraged. When new species are proposed they could provisionally be placed in Ortho seira and later transferred to different genera if required. 3) Formal phylogenetic analysis with molecular and morphological data should be carried out. The phylogenetic relationships from these analyses should be the basis of the classification system for the group.

During a survey of diatoms from the Colombian and Peruvian Amazon, we encountered many specimens of the genus Stenopterobia in periphyton and plankton samples. These diatoms were assigned to three different taxa, two with sigmoid valves and the other one with straight valves. The comparison of their valve morphologies with similar taxa described in the literature revealed that they do not correspond to any previously known taxa. They are described herein as Stenopoterobia caquetaensis sp. nov., S. colombiana sp. nov. and S. amazonica sp. nov. We maintain this genus assignment since the new taxa, as well as other species currently in Stenopterobia, exhibit differences from Iconella, a genus to which several Stenopterobia species were recently transferred. Differences exist between the two genera in their ultrastructural features, such as plain internal valve face and unrimmed internal areolar openings, which do not fully conform to the description of Iconella. Additionally, the robustoid Surirella rafaelii and S. tayronarum, recently described from Colombia, are transferred to Iconella.

Joaquín Frenguelli formó parte en 1923 de una expedición a la Región del Iberá, organizada en el marco de un proyecto nacional, conocido como Proyecto Mollard. Los pormenores del viaje fueron documentados en publicaciones, aportando descripciones técnicas y paisajísticas precisas de las localidades, especialmente de aquellas donde se recolectaron muestras. Una colaboración entre el Museo de La Plata y la Universidad de Colorado (EE.UU.), vinculada a estudiar la flora de diatomeas de agua dulce de Argentina, permitió que en mayo de 2019 se organizara una campaña a esta región, casi 100 años después de la expedición de Frenguelli, posibilitando así la experiencia única de repetir su itinerario. El objetivo principal de este trabajo fue ubicar las localidades originales visitadas por Frenguelli mediante el empleo de tecnologías modernas, tales como imágenes satelitales y sistemas de información geográfica, a fin de colectar en ellas nuevos materiales que servirán para evaluar los cambios ocurridos en los 97 años que median entre ambas expediciones. Para ello, se digitalizó una carta esquemática publicada en 1924 sobre la base de las descripciones en la bibliografía, se georreferenciaron de manera aproximada las localidades visitadas por Frenguelli, ajustando su ubicación a campo mediante la interpretación de las descripciones de los parajes dadas por el autor y, además, se tomaron muestras en los mismos sitios, con registro de sus coordenadas geográficas con GPS. Finalmente, se obtuvieron y procesaron imágenes satelitales cercanas a la fecha de la campaña, a fin de analizar la cobertura vegetal y uso de la tierra actual en toda el área de estudio. El análisis comparativo de todos estos materiales permitió establecer que, si bien grandes áreas se conservan en estado natural, en otras áreas de la región hubo grandes cambios vinculados con la expansión de las áreas urbanas, la disponibilidad de caminos y rutas y, principalmente, cambios significativos en el uso del suelo relacionados mayormente con la forestación. Los resultados obtenidos constituyen, en su conjunto, información de base, muy escasa hasta el presente, para llevar a cabo futuros estudios ambientales en la región.

Diatoms are a diverse group of unicellular microalgae with broad biotechnological and industrial applications. Recent studies have revealed that some species from the genus Halamphora accumulate high quantities of lipids, which make them potentially suitable for biodiesel production. However, due to their high phenotypic plasticity, molecular phylogenetic and ultrastructural analyses are usually needed for precise species identification, which in turn is crucial to define the cultivation strategies to obtain the main target compound. Moreover, the use of diatoms for nutrition, health, and aquaculture requires prior analysis of the potential toxicity of the selected species. In the present study we provide a detailed morphological, molecular, and toxinological evaluations of an Argentinian strain of Halamphora coffeaeformis with potential as feedstock of triglycerides adequate for biodiesel as well as a source of high-value metabolite production, in order to confirm its identification and to define the safety of its biomass in relation to domoic acid production. The obtained results will strengthen and diversify the use of this species in the microalgal market.

Three new species ofLuticolaare described from lotic ecosystems in Andaki Municipal Natural Park, located in the Andean-Amazon region on the eastern flank of the eastern Andes mountain range in Colombia. Size and morphological features of the three new species,L. caquetensisKociolek, Simonato & Nunez-Avellaneda sp. nov.,L. andakiesiorumSimonato, Kociolek & Plata Diaz sp. nov., andL. sinchiiSala, Kociolek & Simonato sp. nov. are provided, based on light and scanning electron microscopical observations, and compared with similar congeners. Species of the genus are organized into groups depending upon whether they possess or lack marginal channels and/or pseudosepta. All the new species possess pseudosepta andL. caquetensisandL. andakiesiorumlack marginal channels. The two latter species share this combination of features withLuticola affinisLevkov et al.,a species described from Brazil. These species thus form a unique group within the genus, offering additional evidence for the unique biodiversity found in this region.

Background and aims: In 2013, blooms similar to those produced by Didymosphenia geminata (Lyngbye) M. Schmidt around the world, were detected in the Grande River basin, Tierra del Fuego province, and in 2014 in de las Vueltas River in Santa Cruz province. The aim of this paper is to analyze the valve morphology and morphometry of these materials to establish if they correspond to D. geminata or to other species of the genus that is producing the massive growth in southern Patagonia. M&M: Samples were collected at Grande River in 2013 and 2015 and, in de las Vueltas River in 2015 and 2016. Samples were analyzed with light and electron microscopy. For morphometric analyses 100 specimens from each sample were measured and statistical analyses were carried out using the R statistical package. Results: The studied populations have the same fine morphology described for other populations collected in Patagonia. Nevertheless, in some sampling sites from Santa Cruz province, we found a morphotype with a markedly smaller size, subcapitated poles, little marked constrictions of the poles, a broad central area (relative to cell size) and 1 to 3 stigmata, that was never reported in South America. Conclusions: The studied populations correspond to D. geminata ssp. geminata Metzeltin & Lange-Bertalot. From a morphological point of view the smaller morphotype present in Santa Cruz belongs to the same subspecies but can be easily misidentified during the routine monitoring programs carried out with light microscope due its size and valve outline.

Halamphora siqueirosii sp. nov. is a marine benthic diatom isolated as a monoclonal culture from a hypersaline evaporation pond at the Guerrero Negro Saltworks, Baja. California Sur, Mexico. Analysis of the valve ultrastructure of this taxon using light and electron microscopy indicated that its uniseriate striae and the density of its dorsal striae are useful characteristics for discriminating H. siqueirosii from other species with similar morphological patterns. The phylogenetic analyses performed with nuclear ribosomal genes, the small (18S) and large subunits (28S), and chloroplast gene ribulose-bisphosphate carboxylase (rbcL) fragments showed that H. siqueirosii is closely related to H. americana, H. calidilacuna and H. incelebrata. Morphological differences between this new species and similar ones are discussed.

Los objetivos de mi tesis doctoral son evaluar la riqueza del genero de diatomeas Luticola en Argentina, explorar las relaciones filogeneticas del mismo e identificar los patrones de distribucion de las especies encontradas en nuestro pais. Para ello mi trabajo se centra en cinco brazos principales, estos son la revision bibliografica, la consulta de colecciones, el analisis de muestras adquiridas a campo, los analisis moleculares a partir de cultivos unialgales y el desarrollo de mapas de distribucion de las especies. Para la revision bibliografica analizare los trabajos en los cuales se citen especies del genero en estudio en el pais. En cuanto a la consulta de colecciones, principalmente trabajare con materiales de la Coleccion de la Division Ficologia, FCNyM, siendo de especial importancia la Coleccion de Diatomeas Argentinas Dr. Joaquin Frenguelli, en la cual se encuentran varios materiales tipos del genero Luticola. Para la obtencion de muestras se realizaran campanas de muestreo a distintas regiones del pais. Se tomaran muestras cualitativas (multihabitat) de perifiton, midiendo altitud, coordenadas geograficas y parametros fisicos y quimicos del agua. Las muestras colectadas seran conservadas en frio y oscuridad hasta ser llevadas al laboratorio. Parte de estas muestras seran utilizadas para realizar analisis con microscopia optica y electronica de barrido y otras para aislamientos y cultivos. Las muestras seran analizadas con microscopio optico (MO) con contraste de fases e interferencia y microscopio electronico de barrido (MEB), para esto es necesario eliminar la materia organica, lo cual se realizara con peroxido de hidrogeno o peroxido de hidrogeno y dicromato de potasio. El material tratado sera montado en Naphrax para su observacion con MO y sobre tacos de vidrio y metalizadas con oro para su estudio con MEB. Por otra parte se estableceran cultivos unialgales en medios de cultivo a temperatura y luz controladas. A partir de aquellos cultivos que prosperen se realizara la extraccion del ADN y se secuenciaran distintos marcadores que se utilizaran para establecer las relaciones filogeneticas del genero. Para establecer los patrones de distribucion de las especies se realizara un Analisis de Parsimonia de Endemismos (PAE) basado en localidades. Los resultados de este analisis se compararan con esquemas biogeograficos establecidos a partir de otros grupos de organismos. Los datos biologicos, fisicos y quimicos seran reunidos en Sistema de Informacion Geografica. Los mapas de distribucion de las especies se realizaran usando el software QGIS.

Introducción y objetivos: Didymosphenia geminata, diatomea declarada “Especie Exótica Invasora” en Argentina por la Secr. Ambiente y Desarrollo Sustentable de la Nación. Esta especie coloniza rocas y puede formar grandes matas mucilaginosas que cubren el lecho de los ríos, ocasionando un considerable impacto estético y provocando serias alteraciones en los ecosistemas. En los últimos 9 años la especie ha colonizado ríos andino-patagónicos y ha aumentado considerablemente su distribución en la región. El objetivo de este trabajo es analizar la dinámica de esta especie en la Patagonia argentina mediante el uso de SIG. M&M: los datos provienen de resultados obtenidos por el grupo de trabajo en las provincias del Neuquén y del Chubut e información abierta y libre disponible en la web. Se generó una base de datos a escala regional abarcando desde Neuquén a Tierra del Fuego. Resultados: fueron incorporados a un SIG, lo que permitió generar mapas de distribución a nivel provincial y nacional. Conclusiones: los datos disponibles hasta marzo de 2018 muestran que D. geminata, ha expandido su distribución entre 2010 y 2018 desde la provincia del Chubut hacia el norte alcanzando la provincia de Neuquén y hacia el sur llegando a Tierra del Fuego.

En este trabajo se presenta el primer registro de la especie Terpsinoë musica y la primera cita del género para Colombia. Los especímenes de T. musica se estudiaron mediante microscopía óptica y electrónica de barrido, se realizó la descripción morfológica y se tomaron los datos morfométricos. Esta alga fue encontrada en muestras de perifiton recolectadas en sistemas lóticos de las regiones biogeográficas de la Orinoquía y el Caribe, asociada a Eichhornia crassipes y Lenna minor, en cuerpos de agua levemente alcalinos, con conductividades eléctricas moderadas y bajos valores de caudal. Se realizó una comparación con otras poblaciones de la especie registradas en América, Europa y África, mencionando aspectos relacionados con sus requerimientos ecológicos y distribución geográfica. El material tipo de la especie no ha sido analizado con técnicas modernas de estudio. Teniendo en cuenta la gran variabilidad morfológica entre distintas poblaciones de la especie y la diversidad de ambientes en los que se registró, se plantea si estamos frente a un taxón con amplia variabilidad morfológica y gran distribución geográfica o, por el contrario, si se trata de un complejo de especies con requerimientos ecológicos y distribuciones más restringidas.

Diploneis Ehrenberg ex Cleve is a diverse genus, with species predominantly from epipelic, marine habitats; there are a few freshwater representatives.In 1933 Frenguelli reported four taxa of this genus at the Esteros del Iberá, a vast subtropical wetland from Argentina.Two of the four taxa reported were new for science.One of the reported species was Diploneis elliptica (Kützing) Cleve (Basionym: Navicula elliptica Kützing) a species cited from very diverse environments of every continent.In this study the type material of Navicula elliptica Kützing, deposited at the Natural History Museum in London, was analyzed with scanning electron microscopy and its valve fi ne structure described.Comparison of this type material with others studied under SEM from America, Europe, Africa and Asia indicate that D. elliptica has been widely misidentifi ed.The materials from Iberá, Argentina, deposited under this name in the Frenguelli´s Collection at the Museo de Ciencias Naturales de La Plata, belong to a new species, described here as Diploneis sudamericana.These two taxa are very similar when analyzed with LM but clearly diff er in the striae and areolae structure.D. sudamericana has uniseriate striae at valve center and biseriate near the valve margin; the alveoli are externally occluded by a unique complex cribrate occlusion.This species also diff ers from others in the areolae of the longitudinal canals and the external proximal raphe ends.

The genus Odontidium is characterized by the presence of robust internal transapical ribs, a wide sternum and a complex cingulum composed by several open bands with ligulae, differentiated in copulae and pleurae. Only two species of Odontidium have been recorded from Argentina. In samples collected in the upper basin of the Diamante River, Mendoza Province the dominant specimens were of this genus but differed from those species already known. Examination of the valve morphology of these specimens, and comparison with other species of the genus, showed it is a new species Odontidium andinum. O. andinum has valves broadly lanceolate to linear with rounded to subcapitate ends. It is similar to O. hyemale, O. mesodon and O. rostratum. Although smaller specimens of all these species are similar when using the light microscope, with a complete size series it is possible to see marked differences in the valves’ outline. These differences correspond with others found in the fine structure of the valves and girdles. These specimens also match those previously named as Diatoma hyemalis (Roth) Heiberg sensu lato, collected in the Chilean Andes and with others recently found in a high altitude river in Argentinean Patagonia, showing the Andean distribution of the species.

In compliance with the Water Framework Directive of the European Union, we needed to diagnose the ecologic quality of the different sections of the nvers of the Guadalquivir basin. In order to establish a regional classification of the water bodies by a grouping into areas of similar charactenstics, we took into consideration the benthic phycologic flora of the Guadalquivrr-River basin. Benthic algae, being one of the groups of organisms that best define the water quality of rivers, are useful for characterizing the basin's ecoregionalization. We collected multihabitat samples in 109 georeferenced reaches and identified 777 algal taxa: 397 Bacillanophyceae (diatoms), 181 Chlorophyta, 148 Cyanoprokanota, 41 Euglenophyta, 4 Chrysophyceae, 3 Dinophyta, 2 Rodophyta, and 1 Cryptophyta. Except for Achnanthidium minutissimum-it being present in nearly all the sites-the species composition enabled the identification of 4 groups: (1) the Sierra-Morena rivers with a predominantly siliceous substrate and concomitantly low mineralized water (< 250 mg/L); (2) the Donana and lower-Guadiamar rivers of the lower-Guadalquivir with a high relative proportion of sodium; (3) rivers with any kmd of disturbance, principally organic contamination, grouped regardless of their geographical location; (4) rivers of high calcium content that, though constituting a heterogeneous group, the majority of which belong to the Betic-Mountain region. According to our results, the subbasin was the one that determined the composition of the periphyton. The categorization of the rivers according to biota obtained in the present work differs from the hydrogeo-morphological classification established by the Guadalquivir Hydrographic Confederation.

Diploneis zannii was first described from the Esteros del Iberá, a subtropical wetland from Argentina. Type material of the species was studied with light and electron microscopy and compared to some similar taxa: D. fusca, D. insolitus, D. lenzii, D. smithii and D. finnica and other material collected from Brazil and Uruguay. We confirm the validity of Diploneis zannii as a species and present an emended diagnosis derived from new information on its morphology. A lectotype and isolectotype are designated.