The marine epilithic diatom Melosira brandinii sp. nov. (Bacillariophyta) from Elephant Island, Antarctic Peninsula, with comments on some related species

Uma nova espécie de diatomácea eplítica é descrita sob microscopia eletrônica, a partir de amostras coletadas próximo à Ilha Elefante, Península Antártica. As células de Melosira brandinii sp. nov. encontram-se reunidas em cadeias filamentosas através de longos tubos mucilaginosos. As valvas são circulares, com superfície valvar provida de lóculos pentagonais arranjados irregularmente. Cada lóculo possui 6-12 poros na superfície externa, abrindo-se para o interior através de aréolas do tipo rota. A corona é composta exclusivamente por grânulos grosseiros, os quais estão mais concentrados na borda do manto. Comparações com as espécies próximas Melosira arctica, M. moniliformis e M. nummuloides foram realizadas. Adicionalmente, são fornecidas fotomicrografias de M. arctica provenientes do material tipo e do Mar de Barents (Ártico), e de M. moniliformis de estuários do Sul do Brasil.A new species of epilithic diatom is described from samples collected near Elephant Island, Antarctic Peninsula. The cells of Melosira brandinii sp. nov. are joined in filamentous chains and attached by means of long mucilaginous stalks. The valves are circular with the valvar surface composed of irregularly arranged pentagonal Ioculi. Each loculus bears 6-12 pores on the external surface, opening to the innerside through rotae. The corona is only composed of coarse granules. A mantle is well developed, presenting rimoportulae and bearing coarse granules, which are more concentrated at the mantle edge. Comparisons with the related species Melosira arctica, M. moniliformis and M. nummuloides are made. Additionally, photomicrographs of M. arctica from the type material and Barents Sea, and of M. moniliformis from estuaries of Southern Brazil are included

Discusión taxonómica de algunas especies interesantes de los géneros Biddulphia Gray y Triceratium Ehrenberg (Bacillariophyceae)

A taxonomic revision of some diatom species of the genera Biddulphia Gray and Triceratium Ehrenberg is made. The species are: B. azorica Pavillard, B. schroederiana Schussnig, B. membranacea Cleve. T. formosum Brightwell f.formosum, T. formosum f. quadrangularis (Hustedt), T. formosum f. quinquelobulata (Hustedt), T. shadboltianum Greville, T. shadbottianum f. elongata (Grunow) Hustedt and T. pelagicum (Schroder) Sournia. These species have poor siliciflcation of the frustules, reduced valvar apendixes and spines or none; these features could be regarded as adaptations to pelagic life. Descriptions and microphotographies of the species were made. These Biddulphia spp were found to be very close and some morphometric differences in the relation apical axe/pervalvar axe were taken in order to identify them quickly. All forms were found to be more frequent in no rain season and in high salinity waters (36 ‰). For T. formosum f. quadrangularis (Hustedt) and T. formosum f. quinquelobulata (Hustedt) some explanations were made about its real infrasnecific position, so that T. quadrangulare Greville and T. quinquelobutarum Greville should be regarded as different species of that forms of T.formosum Brightwell. B. azorica Pavillard and B. schroederiana Schussnig are first reported for the Caribbean Sea area

Eunotiaceae (Bacillariophyceae) em igarapés da Amazônia Central, Manaus e Presidente Figueiredo, Brasil

Estudos florísticos e taxonômicos envolvendo diatomáceas são escassos para a região amazônica. As publicações existentes incluem registros de diatomáceas da Amazônia brasileira, do Equador, da Colômbia e do Peru e comumente mostram que Eunotia e Actinella (Eunotiaceae) são gêneros bem representados nessa região. A maioria dos igarapés amazônicos costuma apresentar potencial hidrogeniônico (pH) ácido, característica aquática que promove o desenvolvimento de uma comunidade típica de diatomáceas, dominada por espécimes de Eunotiaceae. O objetivo deste trabalho foi providenciar um levantamento florístico das espécies de Eunotiaceae presentes em igarapés da Amazônia Central brasileira e registrar os morfotipos de algumas espécies. Amostras fitoplanctônicas e perifíticas foram coletadas em cinco igarapés na rodovia BR-174, em Manaus e Presidente Figueiredo, em setembro e outubro de 1996 e fevereiro e março de 1997. Lâminas permanentes foram preparadas de acordo com a técnica de oxidação lenta para o estudo qualitativo. Vinte e três espécies pertencentes ao gênero Eunotia e seis ao gênero Actinella foram determinadas. Chaves dicotômicas de identificação, descrição detalhada, comentários relevantes e ilustrações foram providenciadas para cada táxon determinado. Morfotipos foram documentados para Eunotia zygodon. Espécies raramente citadas na literatura foram registradas, tais como, Eunotia falcifera e Eunotia rostellata.Floristic and taxonomical studies about diatoms to Amazonian region are commonly well represented by Eunotia and Actinella (Eunotiaceae). The available works include diatom assemblage from Brazilian, Ecuadorian, Colombian and Peruvian Amazonia. The local streams often present acid pH which provides environmental conditions to develop a very particular diatom community dominated by specimens of Eunotiaceae. Thus, the aim of this paper is to give a floristic survey of Eunotiaceae from central Amazonian rivers and to register the typical morphologic frustule variations of some species. Planktonic and periphytic samples were collected from five rivers located at the BR-174 highway, near Manaus and Presidente Figueiredo districts, during 1996 and 1997. Slides were prepared in accordance with the technique of slow oxidation for the qualitative determination. Twenty-three species of Eunotia and six of Actinella were identified. Dicotomic keys, taxonomic comments and photographic illustrations were added. Morphotypes of Eunotia zygodon were registered. Species scarcelly mentioned on diatom literature were registered, such as, Eunotia falcifera and Eunotia rostellata

Centric diatoms of large rivers and tributaries in Hungary: morphology and biogeographic distribution

Centric diatoms of 107 different Hungarian running waters were investigated. Among them the largest was the River Danube, from which more than one hundred plankton samples were analysed by scanning electron microscopy (SEM). Only one sample was analysed from creeks, which were the smallest running waters analysed in this study. There were also channels with slow currents flowing out of rivers or connecting different rivers.In total, 41 centric taxa belonging to 11 genera were found during this study. The average number of taxa found in a single watercourse was 7, the maximum 40 and the minimum 1. Cyclotella meneghiniana was the most frequently encountered species (present in 60% ofsites). Twelve taxa were found in more than 20% of sites, 7 taxa between 5–10% and 6 taxa only in one site