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(Lamark, 1819) is an epibiont filter feeder bivalve. Its fast growth and fast gonadal recovery depend on the amount and quality of the food ingested by the animal, mainly composed of phytoplankton cells. In the coast of Paraná State, Brazil, several aquaculture farms of C. brasiliana can be found along the Paranaguá Estuarine Complex (PEC) and Guaratuba Bay. Therefore, this work had as objectives to evaluate the taxonomic composition and cell size of the microalgae ingested by adults of the oyster C. brasiliana and to describe its reproductive characteristics (index of meat revenue and stages of gonadal maturation). Oysters cultivated in the PEC were acquired monthly from the Municipal Market of Paranaguá. The oysters (n=30) were then measured and shell length values (SL), height (SH) and gross weight (GW) obtained. Gonadal maturation stages were evaluated through the macroscopic examination of the gonads and revenue index (R) through the wet weight of meat. The digestive gland was removed for the microscopic analysis of the stomach content (i.e. identification and measurement of the microalgae). The highest mean R value (12.79 %) was observed in July 2007, when a great portion of the population presented full gonads, although the predominance of individuals with full gonads (partially full and full) occurred in periods of warmer waters. The genera found in the digestive tract were: Nitzchia, Gyrosigma, Navicula, Pleurosigma, Thalassionema, Frustulia, Anomoeoneis, Chroococcus, Cocconeis, Diploneis, Cyclotella, Coscinodiscus and Prorocentrum, with the cell size varying from 5 to 260 µm.

SUMMARY: Mollusc species composition, abundance and spatial distribution were analysed from April 1996 to October 1997 on two tidal flats in Paranaguá Bay (SE Brazil) at the entrance (St. I) (Lat. 25º32'S) and in the intermediate sector (St. II) (Lat. 25º30'S) of the estuary. At St. I, with the highest and least variable salinity, species richness (R = 40) and diversity (H´ = 1; D S = 0.85) were higher than at St. II (R = 22 and H´ = 0.54; D S = 0.57). The tropical clam Anomalocardia brasiliana was the most conspicuous mollusc of the two assemblages, followed by Cerithium atratum, Neritina virginea and Crassostrea sp. at St. I and by Macoma constricta and N. virginea at St. II. On the two flats, the decrease in species richness and abundance towards the upper tidal levels suggests a strong relationship between relative tolerance to physiological stress in the organisms and the degree of immersion/submersion.Key words: Benthic molluscs, species composition, spatial distribution, tidal flats, Anomalocardia brasiliana, Paranaguá Bay, southeastern Brazil. RESUMEN: COMPOSICIÓN Y DISTRIBUCIÓN DE MOLUSCOS BENTÓNICOS EN LLANOS INTERMAREALES DELA BAHÍA DE PARAGUA-NÁ (PARANÁ, BRASIL). -Se ha analizado la composición específica de moluscos, abundancia y distribución espacial en dos llanos intermareales de la bahía de Paraguaná (SE de Brasil), entre abril de 1996 y octubre de 1997, en la boca (estación I) (Lat. 25º32'S) y en el sector intermedio (estación II) (Lat. 25º30' S) del estuario. En la estación I, con la salinidad más elevada y menos variable, la riqueza específica (R = 40) y diversidad (H' = 1; D s = 0.85) fueron superiores a los valores detectados en la estación II (R = 22 y H' = 0.54; D s = 0.57). El bivalvo tropical Anomalocardia brasiliana fue el molusco más conspícuo de las dos zonas, seguido por Cerithium atratum, Neritina virginea y Crassostrea sp. en la estación I y por Macoma constricta y N. virginea en la estación II. En los dos llanos, el descenso en riqueza específica y en abundancia hacia los niveles mareales superiores sugiere una fuerte relación entre la tolerancia relativa al estrés fisiológico en los organismos y en el grado de inmersión/emersión.Palabras clave: moluscos bentónicos, composición específica, distribución espacial, llanos intermareales, Anomalocardia brasiliana, Bahía de Paraguaná, Brasil.

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