Freeze-etching and thin sectioning were used to examine the fine structure of the marine dinoflagellate Peridinium trochoideum (Stein) Lemm. Among the cytoplasmic inclusions described were three typical dinoflagellate organelles: a dinocaryotic nucleus with condensed interphase chromosomes, chloroplasts with thylakoids associated in groups of three, and trichocysts contained in membranous sacs. In addition to the above, dictyosomes, cytoplasmic membrane systems, fibrous bodies and 'segregated bodies' were observed and described. Upon examining the gross morphology of the theca, it was found that thecal age could be determined by the extensiveness of sutures, pits, and blisters which became predominant on the external thecal membranes with age. Characteristically, older cells sometimes had continuous, deeply scored sutures with adjacent 'marginal suture bands' and intercalary bands. Individual thecal plates of mature cells were not completely enclosed within membrane sacs as commonly assumed and some adjacent plates were found to be continuous. Four membrane systems were found to be associated with the thecal plates: the thecal membrane and outer plate membrane systems lay above the plates, the inner plate membrane and plasmalemma lay below. Sutures were formed by infolding of the outer plate membrane between adjacent plates. With the exception of the plasmalemma, the membranes associated with the plates displayed membrane asymmetry. In the mature, thecate,non-dividing cells, densely staining inclusions termed 'pro-thecal bodies' were found to be distributed throughout the cytoplasm. Before ecdysis, each amorphous prothecal body transformed into many vesicles each of which contained fibrous material in an electron transparent matrix. It appeared that the vast number of vesicles so formed may have increased the cell's osmotic pressure enough to initiate ecdysis. At ecdysis, the thecal plates and overlying membranes were lost and the new wall was formed by deposition of material from prothecal bodies at the protoplast surface. The newly formed wall was continuous over the protoplast and no plates existed as such. Pores, however, were present. The sutures, when first formed were shallow and discontinuous. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

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A bacia hidrográfica do Ribeirão das Antas inicia-se na represa das Antas, construída em 1982. A represa das Antas recebe os efluentes tratados da UTM (Unidade de Tratamento de Minério), procedentes de drenagens ácidas geradas em pilhas de rejeitos de urânio. Foi realizada a caracterização limnologica deste corpo aquático visando a determinar o impacto ambiental causado por efluente de mina de urânio lançados pela UTM sobre a represa das Antas. Realizou-se coletas de água durante 1 ano nos pontos Cabeceira-Cab, P41, P14Superfície-P14S e P14Fundo-P14F, sendo avaliadas as variáveis físicas, químicas e biológicas. De acordo com os resultados obtidos para o Índice de estado trófico este corpo aquático foi classificado como oligotrófico e para o Índice de saprobidade foi considerado betamesosapróbico com qualidade da água Classe II. Os resultados das análises químicas mostraram teores elevados de fluoreto, manganês, zinco e sulfato no P41 seguido dos pontos P14S e P14F, estando acima do permitido pela legislação vigente para água de classe II. Estes resultados indicaram possível falha no sistema de tratamento de efluentes desta instalação nuclear e possível impacto ambiental, uma vez que, os menores valores de Índice de diversidade e biomassa média para o protozooplâncton foram detectados no ponto P41. / Ribeirão das Antas hidrographic basin starts on Antas reservoir which was built in 1982. The Antas reservoir receives treated effluents from the UTM (Mineral Unit Treatment), from acid mine drainage generated in piles of uranium waste. Limnological characterization of this aquatic body was done to determine the environmental impact caused by uranium mine effluents. Sampling campaigns were made during one year at the Cab, P41, P14S, and P14F points. Physical, chemical, and biological variables were evaluated. According with the Tropic State Index results obtained this aquatic body was classified as oligotrophic and the saprobity Index classified the water as betamesosaprobic, class II water quality. These results show failures in this nuclear installation effluent treatment system and possible environmental impact, since lower diversity index values and protozooplankton average biomass were detected at P41 point.

A bacia hidrográfica do Ribeirão das Antas inicia-se na represa das Antas, construída em 1982. A represa das Antas recebe os efluentes tratados da UTM (Unidade de Tratamento de Minério), procedentes de drenagens ácidas geradas em pilhas de rejeitos de urânio. Foi realizada a caracterização limnologica deste corpo aquático visando a determinar o impacto ambiental causado por efluente de mina de urânio lançados pela UTM sobre a represa das Antas. Realizou-se coletas de água durante 1 ano nos pontos Cabeceira-Cab, P41, P14Superfície-P14S e P14Fundo-P14F, sendo avaliadas as variáveis físicas, químicas e biológicas. De acordo com os resultados obtidos para o Índice de estado trófico este corpo aquático foi classificado como oligotrófico e para o Índice de saprobidade foi considerado betamesosapróbico com qualidade da água Classe II. Os resultados das análises químicas mostraram teores elevados de fluoreto, manganês, zinco e sulfato no P41 seguido dos pontos P14S e P14F, estando acima do permitido pela legislação vigente para água de classe II. Estes resultados indicaram possível falha no sistema de tratamento de efluentes desta instalação nuclear e possível impacto ambiental, uma vez que, os menores valores de Índice de diversidade e biomassa média para o protozooplâncton foram detectados no ponto P41. / Ribeirão das Antas hidrographic basin starts on Antas reservoir which was built in 1982. The Antas reservoir receives treated effluents from the UTM (Mineral Unit Treatment), from acid mine drainage generated in piles of uranium waste. Limnological characterization of this aquatic body was done to determine the environmental impact caused by uranium mine effluents. Sampling campaigns were made during one year at the Cab, P41, P14S, and P14F points. Physical, chemical, and biological variables were evaluated. According with the Tropic State Index results obtained this aquatic body was classified as oligotrophic and the saprobity Index classified the water as betamesosaprobic, class II water quality. These results show failures in this nuclear installation effluent treatment system and possible environmental impact, since lower diversity index values and protozooplankton average biomass were detected at P41 point.