Eduardo A. Morales

Studies in selected fragilarioid diatoms of potential indicator value from Florida (USA) with notes on the genus Opephora PETIT (Bacillariophyceae)

Four araphid diatom taxa were collected from Florida streams and studied with both light microscopy (LM) and scanning electron microscopy (SEM). Three taxa, formerly in the genus Fragilaria LYNGBYE, are here placed in the genus PseudostaurosiraWILLIAMS et ROUND. On the basis of ultrastructure observed by SEM, the remaining taxon is placed in a new genus, Sarcophagodes. At least two of the species referred to Pseudostaurosiramay have been confused with species of the genus Opephora PETIT, which may have led to misinterpretation of the ecological characteristics of the latter genus. All the taxa treated here belong to the Family Fragilariaceae G REVILLE as delimited in current classification schemes. Two new combinations Pseudostaurosiropsis geocollegarum(= Fragilaria geocollegarumWITKOWSKI et LANGE-BERTALOT), Pseudostaurosira neoelliptica (= Fragilaria neoellipticaWITKOWSKI) and the new species Pseudostaurosira clavatumare presented herein. Additionally, a new genus, Sarcophagodes, is erected to accommodate the new species S. delicatula. LM and SEM details, as well as criteria delimiting these taxa are discussed. More collections and further analyses are needed to assess the distribution of both Opephoraand Sarcophagodes.

Identification of diatoms (Bacillariophyceae) during ecological assessments: Comparison between Light Microscopy and Scanning Electron Microscopy techniques

Abstract Identification of diatom frustules, a vital step during ecological analyses, is greatly influenced by the magnification at which samples are examined. The striking differences between Light Microscopy (LM) and Scanning Electron Microscopy (SEM) reveal inconsistencies in the identification of diatoms at low magnifications. These inconsistencies hinder comparative analyses between data sets collected by several research centers and may be hiding information of potential value in the assessment of ecosystem health. Additionally, SEM research has had a marked impact on diatom taxonomy rendering traditional identification methods insufficient for recognition of newly created taxa. Many diagnostic features of small representatives of these newly erected taxa can not be recognized even at higher LM magnifications. The consequent lack of taxonomic resolution at the LM level may be leading to overestimation of geographical distributions, ranges of tolerance to environmental parameters, and optimal conditions for growth. Qualitative aspects of the differences between LM and SEM approaches are discussed in the present paper.

Observations of the morphology of some known and new fragilarioid diatoms (Bacillariophyceae) from rivers in the USA

Morphological studies at the light microscopy and scanning electron microscopy levels of selected fragilarioid diatoms occurring in North American streams and lakes are presented herein. The majority of the samples studied were collected by the US Geological Surveys National Water Quality Assessment Program, which concentrates on stream water quality monitoring throughout the continental USA and Hawaii. Two new species (Staurosirella confusa Morales and Punctastriata mimetica Morales) and a new forma (Pseudostaurosiropsis geocollegarum f. triradiatum Morales) are described and two new combinations (Pseudostaurosira subsalina (Hustedt) Morales and Staurosirella olden‐burgiana (Hustedt) Morales) are provided. Morphological details of an additional taxon, Staurosira construens var. binodis (Ehrenberg) Hamilton in Hamilton et al. are also presented. The taxonomic affinities of all these taxa, as well as some evolutionary aspects and ecologic characteristics, are discussed in the light of published material.

Studies in selected fragilarioid diatoms (Bacillariophyceae) from Lake Hovsgol, Mongolia

Three fragilarioid diatom taxa were studied in detail at the light microscopy and scanning electron microscopy levels from samples collected from Lake Hovsgol, Mongolia. Two of the taxa are new to science, described here as Staurosirella minuta Morales et M. B. Edlund and Pseudostaurosira tenuis Morales et M. B. Edlund, and may be endemic to Lake Hovsgol. The third taxon has been identified as Fragilaria polonica Witak et Lange‐Bertalot and it is transferred to the genus Pseudostaurosira (Grunow) D. M. Williams et Round as Pseudostaurosira polonica (Witak et Lange‐Bertalot) Morales et M. B. Edlund comb. nov. based on the ultrastructural features of its valves. The relationship of the above taxa to others reported in the literature is included herein, and the nomenclatural transfer, Pseudostaurosira naveana (Le Cohu) Morales et M. B. Edlund comb. nov., is proposed.

Notes on the genus Nupela (Bacillariophyceae) including the description of a new species, Nupela scissura sp. nov. and an expanded description of Nupela paludigena

Two species of the diatom genus Nupela are reported from freshwater lakes situated along the Atlantic Coastal Plain of North Carolina, USA. One of the species, N.u2003scissura sp. nov., is described as new and the description of the other, Nupela paludigena (Scherer) Lange‐Bertalot, is expanded to include a full suite of ultrastructural characters. Nupela scissura is a heterovalvar taxon with one valve having a fully developed raphe identical in structure to those found on other Nupela species. The other valve lacks a true raphe, but presents one to several elongated slits in the apical portion of the sternum. The true identity of the slits, whether they represent a highly reduced raphe, a rudimentary raphe, or neither is unknown. In addition, both valves of a single N.u2003scissura frustule differ in the structure of the axial and central areas. The structure of the areolae and details of the raphe clearly place this species in Nupela. Nupela paludigena (Scherer) Lange‐Bertalot was originally described in the genus Anomoeoneis from acidic and humic localities from the south‐eastern part of the Atlantic Coastal Plain and later transferred to Nupela. Although this species has rarely been reported since its description, our findings indicate that it is a common component of the floras in the Carolina bays of North Carolina. The characteristics currently used to circumscribe taxa within the genus Nupela are discussed in light of published work and our own observations.

Description and ultrastructure of araphid diatom species (Bacillariophyceae) morphologically similar to Pseudostaurosira elliptica (Schumann) Edlund et al.

Several populations identified and reported from North America and Mongolia under the names Fragilaria elliptica Schumann or Staurosira elliptica (Schumann) Williams et Round were analyzed in detail using light microscopy (LM) and scanning electron microscopy (SEM). The analysis yielded three variants that can not be ascribed to ‘elliptica’ of the type. Furthermore, two of the variants could not be related to published taxa and we describe them as new species, Staurosira ambigua sp. nov. and Staurosira dimorpha sp. nov. A third variant was identified as Pseudostaurosira trainorii Morales, a taxon originally reported from ponds and a river in the north‐eastern USA. The combined LM and SEM analysis used here allowed for a more thorough circumscription of taxonomic boundaries among morphologically similar taxa and for better delimitation of their geographic distributions. A discussion of the taxonomy and ecology of these taxa based on literature and recent ecological data is presented.

SMALL PLANOTHIDIUM ROUND ET BUKHTIYAROVA (BACILLARIOPHYCEAE) TAXA RELATED TO P. DAUI (FOGED) LANGE-BERTALOT FROM THE UNITED STATES

Small species of the genus Planothidium are difficult to identify using light microscopy (LM) due to similarities in valve outline and other structural features. In recent years, application of scanning electron microscopy (SEM) techniques has allowed the distinction and clarification of taxonomie boundaries among several of these taxa, but some taxonomic confusion still remains unresolved in the literature. The present work focuses on species found in samples from U.S. streams and rivers and presents three new combinations (Planothidium conspicuum (Mayer) Morales, Planothidum lemmermannii (Hustedt) Morales, and P. minutissimum (Krasske) Morales) and morphological details and discussions based on literature for two additional species (Planothidium daui (Foged) Lange-Bertalot and Planothidium granum (Hohn et Hellerman) Lange-Bertalot).

MORPHOLOGICAL STUDIES OF DISTRIONELLA INCOGNITA (REICHARDT) WILLIAMS (BACILLARIOPHYCEAE) FROM NORTH AMERICA WITH COMMENTS ON THE TAXONOMY OF DISTRIONELLA WILLIAMS

Detailed morphological observations at the light microscopy (LM) and scanning electron microscopy (SEM) levels were made on North American populations of Distrionella incognita (Reichardt) Williams (=Fragilaria incognita Reichardt). Results are used to show the distinctiveness of this taxon from closely related species and to justify its separation from Fragilaria Lyngbye as suggested by Williams (1990a). The protologue of Distrionella Williams is herein emended to include features newly discovered under SEM. Likewise, two recently described species and a form, Fragilaria germainii Reichardt and Lange-Bertalot, Fragilaria husvikensis Van de Vijver, Denys et Beyens, and Fragilaria germainii fo. acostata Lange-Bertalot are here transferred to Distrionella based on LM and SEM data presented by their original authors. Relationships among these taxa and other morphologically related species are discussed in this work. Ecological attributes are provided for habitats that support Distrionella incognita in North America.

Staurosira stevensonii sp. nov. (Bacillariophyta), a new taxon from Florida, USA

A new species, Staurosira stevensonii, is described from Florida. USA. This new taxon was first found during examination of depositional material from Lake Okeechobee and lately in recent collections from a number of additional localities. Light and scanning electron microscopy indicate a clear relationship with species in the genus Staurosira. Some of the characteristic features of the new taxon include an elegantly cruciform valve outline, slightly capitate valve poles, a constant number of 6 areolae in 1 μm, highly reduced apical pore fields, and open ends between neighbouring cells caused by the reduced size of spines at the valve apices. A higher relative abundance was recorded in bogs and marshes, which indicates the preference of this taxon for acidic environments.

Three New Araphid Diatoms (Bacillariophyta) from Rivers in North America

ABSTRACT. Three new diatoms from North American rivers are described: Staurosira reimeri, Staurosirella elegantula and Staurosirella magna. The features of these diatoms are distinctive, and although they are reported here for the first time, misidentifications and lumping with other taxa in the past are likely. The finding of these three new taxa has two main implications: 1) knowledge of the diversity of araphid diatoms in the Fragilariaceae in North America is still incomplete, and 2) the full set of characters for araphid genera such as Staurosira and Staurosirella is still unknown since the three species described here have novel characters that were unknown or uncommon until the present study. The morphology of the new taxa is shown using light microscopy (LM) and scanning electron microscopy (SEM) and compared with the available literature on this group. S. reimeri is unique within Staurosira because it includes rhomboid, isopolar valves with a narrow linear axial area, rudimentary spines, and apical pore fields reduced to two slits located perpendicularly on the valve mantle edge at the valve apices. S. elegantula and S. magna are unique within Staurosirella due to their large and heavily silicified valves. Both taxa are also shown here to have thick spines with less densely silicified cores, a first report of this feature for Staurosirella. Additionally, S. magna has copulae possessing well developed ligulae that can be folded outwards, a feature that has not been seen in any other published taxa within Staurosirella. Finally, two varieties are transferred to the genus Staurosirella at the species level: S. dubia and S. rhomboides, based on a previous study of these diatoms in North American material done at the LM and SEM levels. New taxa: Staurosira reimeri Morales, Manoylov et Bahls, Staurosirella elegantula Morales et Manoylov, Staurosirella magna Morales et Manoylov. New combinations: Staurosirella dubia (A. Grunow) Morales et Manoylov, Staurosirella rhomboides (A. Grunow) Morales et Manoylov.