Abstract
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.
Highlights
The morphological identification of Thalassiosira species is mainly based on ultra-structure details like the number and location of the rimoportulae and fultoportulae processes on the valve
Of the six Thalassiosira species, only T. hendeyi and T. minuscula were previously reported in the southernmost Brazilian shelf slope, on the Uruguayan border (Lange and Mostajo, 1985)
T. hendeyi was reported in northern Brazil (Franco, 1991), and Ribeiro (1996) recorded T. cf. minuscula as a frequent species in the subtropical Brazilian shelf (16°-26° S)
Summary
The morphological identification of Thalassiosira species is mainly based on ultra-structure details like the number and location of the rimoportulae and fultoportulae processes on the valve. Examination of the frustules in the electron microscope (EM) is essential for identification of most species, as recognized since the first transmission and scanning electron microscopy studies of Thalassiosira respectively in the 1950s and 1960s (Helmcke and Krieger, 1953; 1954; Hasle, 1968). EM analysis greatly enhanced taxonomy fundaments and morphological details important for the recognition of Thalassiosira species and the identification of more than. On the Brazilian coast, thirty seven marine and brackish water taxa were cited but only five of them, T. oestrupii (Ostenfeld) Cleve, T. nanolineata (Mann) Fryxell and Hasle, T. eccentrica (Ehrenberg) Cleve, T. p unctigera (Castracane) Hasle and T. oestrupii var. The highest number of Thalassiosira species was found in the southern Brazilian shelf and slope waters near the boarder with Uruguay (38° 12’ S and 57° 15’ W-39° 59’ S, 54° 11’ W; 22 species, Lange and Mostajo, 1985) and along the coast of Paraná State (25° 20’-25° 55’ S and 48° 10’ S-48° 35’ W; 24 species, Procopiak et al, 2006)
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