Search

A population of Amphora micrometraGiffen, collected in September 2002 from different habitats in Laguna Blanca in the Bolivian Altiplano, South America, has been examined using light transmission and scanning electron microscopy. The original description of this species is incomplete and insufficient to characterize the taxon in the light of the newly collected ultrastructural data. The holotype of A. micrometrawas examined during the present study and compared to Bolivian specimens. An emended diagnosis of A. micrometrausing all available information is provided. A taxonomic discussion based on available literature and the ecology of the taxon is also presented herein.

Small species of the genus Planothidiumare 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 at the light microscopy (LM) and scanning electron microscopy (SEM) levels of selected fragilarioid diatoms within the genus StaurosirellaWilliams et Round occurring in North American streams and rivers are presented herein. The studied samples were collected by the U.S. Geological Survey's National Water Quality Assessment Program (NAWQA), which concentrates on stream water quality monitoring throughout the continental United States and Hawaii. Two new species (Staurosirella ovataMorales and Staurosirella subrobustaMorales), one new combination (Staurosirella martyi(Héribaud) Morales), and three new combinations/new status (Staurosirella dubia(Grunow) Morales, S. rhomboides(Grunow) Morales, and S. subcapitata(Frenguelli) Morales) are presented. Additionally, detailed morphological information of one additional taxon (Staurosirella leptostauron(Ehrenberg) Williams et Round,) is provided. The taxonomie affinities of all these taxa, as well as some ecological aspects are discussed in the light of published and newly collected material.

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 incognitaReichardt). Results are used to show the distinctiveness of this taxon from closely related species and to justify its separation from FragilariaLyngbye as suggested by Williams (1990a). The protologue of DistrionellaWilliams is herein emended to include features newly discovered under SEM. Likewise, two recently described species and a form, Fragilaria germainiiReichardt and Lange-Bertalot, Fragilaria husvikensisVan de Vijver, Denys et Beyens, and Fragilaria germainiifo. acostataLange-Bertalot are here transferred to Distrionellabased 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 incognitain North America.