Lucina floridana is an intertidal clam that contains intracellular, sulfur-oxidizing symbiotic bacteria in its gills. These bacteria are chemolithoautotrophic, using the energy from the oxidation of reduced sulfur compounds to power carbon fixation. Although sulfide is an energy-rich compound, it is also toxic to aerobic metabolism and autooxidizes in the presence of oxygen. Flow-through experiments were designed to examine the metabolic response to sulfide of the intact symbiosis. Three questions were addressed: 1) What are the major sulfide oxidation products in the gill and in the hemolymph? 2) How are sulfide and its major oxidation products distributed between the hemolymph and the gill? and 3) What is the metabolic poise (use of aerobic or anaerobic metabolism) in the gills during sulfide oxidation? The production of sulfide in the gills in response to various sulfur starvation regimes was also examined. Sulfide and its major oxidation products were determined using HPLC analysis of incompletely oxidized sulfur compounds. The metabolic poise was assessed by measuring the concentrations of substrates and products of anaerobic metabolism. Sulfide was produced in the gills of Lucina floridana after five days of sulfur starvation. The addition of invertebrate feed, a source of organic carbon for the clams, to the seawater significantly reduced the concentration of sulfide in the gills following sulfur starvation, suggesting that sulfide production was a consequence of symbiont oxidation of reduced sulfur compounds in the gills to provide energy for carbon fixation. Sulfide was oxidized to thiosulfate which was preferentially distributed in the hemolymph relative to the gills, a pattern that is consistent with further oxidation of thiosulfate by the bacteria in the gills for energy generation. This study was the first to investigate the metabolic poise of a lucinid in response to varying oxygen and external sulfide treatments; evidence suggests that anaerobic metabolism may be an important metabolic mode for Lucina floridana. / Graduation date: 1998

Submitted by Mendes Eduardo (dasilva@ufba.br) on 2013-08-20T15:19:27Z No. of bitstreams: 1 Dissertacao_Simone Franco Rondinelli.pdf: 1108660 bytes, checksum: b44c0207b461bcd48341159bdf12f82d (MD5) / Approved for entry into archive by Alda Lima da Silva(sivalda@ufba.br) on 2013-08-20T20:57:10Z (GMT) No. of bitstreams: 1 Dissertacao_Simone Franco Rondinelli.pdf: 1108660 bytes, checksum: b44c0207b461bcd48341159bdf12f82d (MD5) / Made available in DSpace on 2013-08-20T20:57:10Z (GMT). No. of bitstreams: 1 Dissertacao_Simone Franco Rondinelli.pdf: 1108660 bytes, checksum: b44c0207b461bcd48341159bdf12f82d (MD5) / Fapesb / Recursos pesqueiros constituem importante fonte de renda e proteína indispensáveis à subsistência de populações tradicionais da zona costeira. Na Vila de Garapuá - BA, a lambreta, Lucina pectinata, é o principal recurso explorado nos manguezais. O presente estudo teve como objetivo testar se em áreas menos exploradas, os indivíduos de L. pectinata teriam maiores densidades e maiores comprimentos, e se houve diminuição entre cpues anuais. Foram realizadas amostragens mensais em dois habitats (canais e quizangas) em seis áreas de manguezal através de quadrados aleatórios. Os resultados indicaram que áreas mais próximas apresentaram densidades significativamente menores do que áreas mais afastadas. As densidades foram significativamente maiores nas quizangas, indicando que os indivíduos são mais facilmente capturados nos canais e/ou que os indivíduos ocorrem naturalmente em maiores densidades nas quizangas. Houve um aumento significativo na cpue mensal de lambreta, de 18,2 (2001) para 19,3 dz./marisqueira/dia (2007), indicando que este estoque parece não estar sendo sobre-explorado. Todavia, as marisqueiras mais antigas relatam uma queda em sua captura diária, uma vez que esta espécie vem sendo explorada comercialmente há mais de 30 anos. Dessa maneira, a diferença de densidade entre áreas próximas e distantes à vila pode ser um efeito da exploração constante ao longo dos anos. / Salvador (BA)