Distribuição sazonal e reprodução de Neocorbicula limosa (Maton) (Bivalvia, Corbiculidae) no Lago Guaíba, Rio Grande do Sul, Brasil Seasonal distribution and reproduction of Neocorbicula limosa (Maton) (Bivalvia, Corbiculidae) in the Guaíba Lake, Rio Grande do Sul, Brazil

<abstract language="eng">Neocorbicula limosa (Maton, 1811) is the only species of that South American genus that occurs in the hydrographic basins of Rio Grande do Sul State, Brazil. Seasonal quantitative collections between 1995 and 1996 in the lake Guaiba were accomplished, with the aim to know the reproductive dynamics and environmental preferences of populations of N. limosa. A substratum constituted by medium to coarse sands at an 'average depth around 2m shown to be favorable to installation of population of N. limosa. The largest population density (2.496 ind./m²) was registered in summer. Embryos at various development phases were registered inside individuals. The shell sizes of these individuals started from 8mm in length. The embryo's size could reach ¼ of the shell-mother's size, and their liberation occurs through the rupture of the gills