Biogeographical interpretation of the distribution of Littoridina (Hydrobiidae), in coastal lakes of Rio Grande do Sul, Brazil

Abstract

This work aimed to a biogeographical and autecological survey concerning the influence of salinity on Littoridina distribution in the lagoons of Rio Grande do Sul Coastal Plain. Salinity was determined in 71 sample-points corresponding to 42 lagoons, lagunes and connection channels, in the area between Itapeva Lagoon and Peixe Lagoon, through measurements and collections with longitudinal and daily (seasonal) profiles, from November 1978 to March 1980. Concomitantly molluscs were collected and other abiotic parameters were measured. In order to verify the interrelationship between Littoridina distribution and salinity, laboratory bio-assays were carried out, with the collected and acclimatized individuals being submitted to several concentrations. Particular methodological procedures were developed. The present work shows the importance of salinity on biogeographical interpretation of freshwater and brackish water molluscs distribution in Rio Grande do Sul coastal region, using field surveys combined to laboratory autecological tests, and demonstrates the possibility of utilizing the studied species molluscs as salinity bioindicators