Abstract
Thalassiosira is a large diatom genus intensively studied since the 1970s, being well represented in diverse marine environments worldwide. Despite the long Brazilian coastline, about 8,500km, few taxonomic works have been performed to investigate the morphology of Thalassiosira species using electron microscope techniques. In this paper the mucilaginous species Thalassiosira diporocyclus, T. mala and T. minuscula were examined in light and electron microscopes, based on material gathered from South Brazilian waters, to record their frustule morphological variability. Some unrecorded findings related to the cribra structure and the cingulum bands are shown. T. mala has central areolae bearing fewer cribral pores than those located in the marginal region. In addition, the valve metrics of T. diporocyclus and T. minuscula are extended in relation to that reported in the current literature. The two species are new records for Brazilian waters, and T. diporocyclus is a new one in the Western Atlantic Ocean.
Highlights
Since the seminal studies of Helmcke & Krieger (1953; 1954) and Hasle and Fryxell (Hasle 1972a; Hasle & Syvertsen 1997 and references therein) using electron microscopy to unveil the fine structure of valve and cingulum of Thalassiosira Cleve, much knowledge has been gathered about genus morphology
Even in South Brazil, where many investigations focusing on diatom taxonomy have been carried out, only a few works are available for Thalassiosira using electron microscopy (Torgan & Santos 2006, 2007; Garcia & Odebrecht 2099a, 2009b)
Our sampling grid covered all the seasonal oceanographic variability described above, in the Paraná shelf waters. In this first report we describe three abundant small species of Thalassiosira from South Brazilian shelf waters, aiming to record their morphological variability and to compare their metric data with material from other marine environments based on the current literature
Summary
Since the seminal studies of Helmcke & Krieger (1953; 1954) and Hasle and Fryxell (Hasle 1972a; Hasle & Syvertsen 1997 and references therein) using electron microscopy to unveil the fine structure of valve and cingulum of Thalassiosira Cleve, much knowledge has been gathered about genus morphology. Even in South Brazil, where many investigations focusing on diatom taxonomy have been carried out, only a few works are available for Thalassiosira using electron microscopy (Torgan & Santos 2006, 2007; Garcia & Odebrecht 2099a, 2009b). Previous contributions relied on light microscope observations, generating basic surveys and checklists (Moreira Filho et al 1990). These authors listed 12 species and 2 varieties in South Brazil. Procopiak et al (2006) reviewed the Luciano Felício Fernandes and Edinara Katiussia Frassão-Santos studies on the diatoms of Paraná coastal waters spanning from 1918 to 2005, and recorded 20 species and 5 varieties, all of them identified through light microscopy. Garcia & Odebrecht (2009b) recorded 17 species in Rio Grande Sul
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