<![CDATA[During January and February 2010 lipophilic shellfish toxins were detected in two bivalve species from Villa Gesell and Mar Azul (Argentina) by the mouse bioassay method and potentially toxigenic species of Dinophysis were consistently found with densities of the order of 10³ to 10(4) cell l-1 in the phytoplankton. Additionally, three cases of human gastrointestinal illness associated with the consumption of cooked wedge clams (Donax hanleyanus) collected in Villa Gesell were reported. The consumed shellfish was positive for lipophilic toxins by the mouse bioassay and the human diseases were consistent with diarrhoetic shellfish poisoning (DSP). This is the first record of detection of an outbreak of diarrhoetic shellfish poisoning associated to the presence of Dinophysis species in Argentina. The species identified were Dinophysis acuminata and D. caudata, previously associated to the detection of diarrhoetic toxins in clams (Mesodesma mactroides), wedge clams and mussels (Mytilus edulis) from the coastal waters of Uruguay.]]>

Colonies that could be identified as Thalassiosira rotula, others that could be identified as Thalassiosira gravida and colonies with a mixture of the valve structures of these two species were found coexisting in the same samples from Piedras Coloradas (40°50′46″S, 65°06′18″W). Net samples were collected from surface water at several stations in the northern area of San Matías Gulf in the Río Negro Province, Argentina, from April 1998 to May 2000 and from March 2006 to April 2007. Untreated and cleaned diatom samples were examined using light and scanning electron microscopy. The differential features used to distinguish T. rotula and T. gravida were discussed and refuted with morphological evidence. Based on this analysis, both taxa are assumed to be conspecific by sharing fultoportulae pattern and morphology of the cingulum. Thus, the name of the species must be T. gravida by the principle of priority. A revision of the original material of T. gravida from Baffin Bay was carried out with light microscopy. The original figure 14 was designated as lectotype and the slide no. 64 of the Tempère and Peragallo Collection (2nd edition) curated at the Muséum National d'Histoire Naturelle in Paris was designated as epitype.

Two strains of Prorocentrum texanum (LPCc020 and LPCc032) were established from coastal waters of the Province of Buenos Aires, Argentina. Field and cultured materials were examined using light and scanning electron microscopy, and the planktonic species Prorocentrum texanum, a known okadaic acid producer, was identified. We compared morphology, genetics and toxin profile of P. texanum based on material from Argentina in relation to strains from the Gulf of México. Our specimens and those described in the protologue of P. texanum var. texanum had similar shape, thecal ornamentation distribution patterns of large and small pores, and morphology of wings supported by platelets 1 and 4, respectively. Morphometric differences occurred in the ranges of length, depth and diameter of thecal plate pores. Morphology of the periflagellar area was described from Argentinean strains. SSU, ITS and LSU rDNA-based phylogenies of strains LPCc020 and LPCc032 placed them with other sequences of P. texanum. ITS rDNA showed that the most closely species, in order, are P. micans, P. steidingerae, P. mexicanum/P. rhathymum, and P. koreanum. The ability of the Argentinian strains to produce marine biotoxins was assessed, but, no toxins were detected. This is the first report of P. texanum outside the Gulf of México.

A new species of the marine dinophyte genus Heterocapsa Stein is described. Two clonal strains originating from Argentinean coastal waters were examined with light and electron microscopy and LSU and ITS rDNA sequence data were obtained. Heterocapsa claromecoensis sp. nov. is described as a distinctive species with a conical epitheca, a similar sized and rounded hypotheca, a single reticulate chloroplast situated in the periphery of the cell, and a large pyrenoid in the episome, above an ellipsoidal to rounded nucleus in the hyposome. The plate tabulation pattern of Po (pore plate), cp (cover plate), X (X-plate or canal plate), 5ꞌ, 3a, 7ꞌꞌ, 6c, 5s, 5ꞌꞌꞌ, 2ꞌꞌꞌꞌ was as for most other species of Heterocapsa. H. claromecoensis sp. nov. differs from all other species of Heterocapsa by the microarchitecture of two different types of organic body scales, which uniquely were different in height. Phylogenetic trees based on LSU and ITS rDNA sequences placed H. claromecoensis in a separate branch, with a sequence assigned to H. orientalis being the closest match based on LSU rDNA.

While conducting surveys of marine phytoplankton from coastal waters of the Anegada Bay (Province of Buenos Aires, Argentina) we found several eupodiscoid diatoms belonging to the genus Odontella sensu lato. Raw and cleaned samples collected at Los Pocitos, Ría del Jabalí and San Blas between 2008 and 2010, were analyzed with light and scanning electron microscopy. Based on a morphological analysis, species with loculate areolae and ocellus-bearing elevations are included in the genera Trieres (T. mobiliensis and T. sinensis) and Zygoceros (Zygoceros atlanticus comb. nov.), while species with poroid or pseudoloculate areolae and ocellus-bearing elevations are provisionally included in Odontella (O. longicruris, O. obtusa and O. rostrata). Zygoceros is revisited based on analysis of type material of species previously included in Odontella (O. atlantica, O. rhomboides and O. rhombus), their description is emended, and correct names of the transferred species are established (Zygoceros atlanticus comb. nov. and Z. ehrenbergii nom. nov.). Trieres differs from Zygoceros by having a ridge between its valve surface and mantle, longer slender polar elevations, longer external rimoportula tubes, and a planktonic style life. Following transfer of taxa with loculate areolae to Trieres and Zygoceros, Odontella only includes species with poroid and pseudoloculate areolae. Further research is necessary to establish the circumscription of Odontella, thus our conclusions are provisional.