Marinês Garcia

PSAMMOCOCCONEIS, A NEW GENUS OF BACILLARIOPHYTA FROM BRAZILIAN SANDY BEACHES

The new genus is characterised by the presence of a valvocopula with straight and smooth margins and by round and transapically elongated pores on its surface. The valvocopula fits beneath the raphe valve and covers the valve areolae and even sometimes the raphe. The internal and external raphe ends are simple. The areolae are occluded by fine porous hymenes on the raphid valve and they are coarser on the araphid valve. Two types of areolae are present around the margin of the araphid valve. The new genus is described from Brazilian sandy beaches (Porto Belo, Brazil) and Cocconeis disculoides Hustedt is transferred to Psammococconeis, establishing a new combination.

DIVERSITY AND MORPHOLOGY OF SKELETONEMA SPECIES IN SOUTHERN BRAZIL, SOUTHWESTERN ATLANTIC OCEAN1

We examined the morphology of Skeletonema species occurring in coastal waters of southern Brazil, on the basis of LM, SEM, and TEM analyses of six isolated strains and of 13 field samples from the Patos Lagoon estuary and the adjacent Cassino Beach. We concluded that the genus Skeletonema is highly diverse in coastal waters of southern Brazil, with the occurrence of four confirmed species: S. costatum, S. pseudocostatum, S. potamos, and S. tropicum. In addition, EM details must still be provided for S. menzelii, and genetic studies should be conducted to confirm the identity of S. cf. grethae and S. subsalsum. The high diversity in this geographic area can be attributed to the proximity of the Subtropical Convergence and to the freshwater ecosystems of Patos Lagoon and La Plata River that favor the presence of warm‐, cold‐, and brackish‐water species.

The transfer of Fragilaria obtusa Hustedt to the genus Staurosira Ehrenberg (Bacillariophyceae)

The ultra‐structure of the frustule of the rarely recorded diatom Fragilaria obtusa Hustedt was studied in detail using sand samples from Laranjal Bay (Lagoa dos Patos Rio Grande do Sul State, Brazil). F. obtusa is transferred to the genus Staurosira Ehrenberg as Staurosira obtusa (Hustedt) Garcia. The taxon is characterized by striae composed of elliptical areolae that are occluded by an internal velum, apical pore field formed by several rows of rimmed pores, girdle bands free of ornamentation, wide valvocopulae, and absence of rimoportulae. This is the first record of S. obtusa from an epipsammic habitat.

Morphology and ecology of Thalassiosira Cleve (Bacillariophyta) species rarely recorded in Brazilian coastal waters

The detailed description of rarely recorded Thalassiosira species in Brazil is presented with light microscope (LM) and scanning electron microscope (SEM) illustrations. A total of 78 phytoplankton net samples (20 microm) collected between the years 2000 and 2006 in coastal waters of southern Brazilian, Cassino Beach and the estuary of Lagoa dos Patos, were studied in cleaned material using the Axiovert Zeiss LM and Jeol 6060 SEM. Water temperature and salinity of samples and six species are presented: Thalassiosira endoseriata, T. hendeyi, T. lundiana, T. minuscula, T. oceanica and T. wongii. Two species, Thalassiosira hendeyi and T. endoseriata were the most common being observed in all seasons at Cassino Beach in a wide temperature range (10-26 masculineC), while only sporadically in the estuary of Lagoa dos Patos. Thalassiosira endoseriata, T. lundiana, T. oceanica and T. wongii are for the first time reported in Brazilian coastal waters. The latter two species, rarely recorded in the world, are fully illustrated based on Brazilian material.

PARALIA ELLIPTICA SP. NOV., AN EPIPSAMMIC DIATOM FROM SANTA CATARINA STATE, BRAZIL

This paper is part of a Ph.D. thesis at Universidade Federal do Rio Grande do Sul A new centric diatom, Paralia elliptica Garcia, is described from marine surface sand collected in Zimbros Bay, Araçá, Penha, Praia Brava and Taquarinhas (Santa Catarina State, Brazil), where it lives as an epipsammic species. The taxon is characterized by its elliptical outline, convex valve, gently undulate valve face with parallel ridges and grooves, heterovalvy and a ring of rimoportulae oriented obliquely to the striae. The morphology and ultrastructure of valves and frustules are described by light microscopy (LM) and scanning (SEM) and transmission electron microscopy (TEM) observations.

LEMNICOLA HUNGARICA (GRUNOW) ROUND & BASSON FROM SOUTHERN BRAZIL: ULTRA-STRUCTURE, PLASTID MORPHOLOGY AND ECOLOGY

Lemnicola hungarica (Grunow) Round & Basson taken from brackish and freshwater environments in Southern Brazil was studied for its ultra-structure details, plastid morphology, and ecology. Previously undescribed details are given: a ring of elongated areolae on the mantle of L. hungarica and its plate-like plastid that lies on the araphid valve where it reaches the valve margin and curves itself towards the raphid valve. Lemnicola hungarica thrives in truly freshwater conditions where conductivity values are below 300 μS/cm, and where floating plants are also present.

ARAPHID PSAMMIC DIATOMS FROM BRAZILIAN SANDY BEACHES I: AN EMENDED DESCRIPTION TO GENUS PRAVIFUSUS WITKOWSKI, LANGE-BERTALOT & METZELTIN

The original diagnosis of Pravifusus Witkowski, Lange-Bertalot & Metzeltin was based on a few light and electron micrographs but several important details for its precise identification were missing. A careful review of Giffen (1975) and his collection slide (BM 80508—Giffenn. 628) showed that Pravifusus occurs also in South Africa where it was described as Campylosira inane Giffen. Pravifusus description is emended with more ultrastractural details provided by light, scanning and transmission electron microscopic observations of Brazilian and South African specimens. Its possible phylogenetic relationship with other closely related genera as Porannulus Hamilton & Poulin is discussed.

Remarks on the morphology and distribution of some rare centric diatoms in southern Brazilian continental shelf and slope waters

This paper provides information on the morphology and occurrence of extant diatoms of the family Asterolampraceae and Azpeitia species of the southernmost Brazilian continental shelf and slope waters in the Southwestern Atlantic Ocean (28 -34oS), under the influence of Tropical, Subtropical, Subantarctic Waters, terrestrial discharges from La Plata River and Lagoa dos Patos lagoon. Plankton was sampled (20 µm net; vertical hauls) at the same 27 stations in winter 2005 and summer 2007. Among Asterolampraceae, Asteromphalus flabellatus was the most frequent species (57% of samples) observed mainly in winter samples (92%) in Subtropical Shelf Water but also under the influence of La Plata River plume (salinity <35). Lower frequencies were observed for Asterolampra marylandica, Asteromphalus elegans, Asteromphalus heptactis and Spatangidium arachne. Four species of Azpeitia were observed: A. barronii and A. neocrenulata for the first time in the South Atlantic Ocean while A. africana and A. nodulifer had already been registered in equatorial and southern areas of Brazil. All Azpeitia species were rare (19%) in offshore samples (100-200 m depth. Remarks on the morphology based on light and scanning electron microcopy observations are provided along with their distribution in the study area.

Chave dicotômica ilustrada para a identificação de espécies de Thalassiosira Cleve (diatomácea) no estuário da Lagoa dos Patos e área costeira adjacente (Rio Grande do Sul, Brasil)

The paper presents a dichotomous key and a comparative table summarizing dimension data and diagnostic characteristics of seventeen Thalassiosira species (diatoms) commonly found in Lagoa dos Patos estuary and the coastal adjacent area (~32° S and 52° W). For all studied species, optic microscope illustrations and comments on significant morphological features are provided, together with scanning electron microscopy images.

Seminavis atlantica Garcia, a new psammic diatom (Bacillariophyceae) from southern Brazilian sandy beaches

The paper presents the description of Seminavis atlantica Garcia, a psammic marine diatom from dissipative sandy beaches from southern Brazil. It is characterized by its convex linear dorsal margin (37 to 50% of its length is in a straight line), linear ventral margin and raphe located very close to the ventral margin. Its morphology is compared to similar species such as Amphora clevei Grunow, Amphora angusta (Greg.) Cleve var. orientalis Allem, Amphora ventricosa Gregory and Amphora eulesteinii Grunow.