Substratum as a factor in the distribution of two prosobranch freshwater snails,Viviparus bengalensis and Melania scabra

Laboratory experiments were conducted to ascertain the substratum preferendum of Viviparus bengalensis and Melania scabra. When the food (Spirogyra) was offered both on stones and sand, the average distribution of V. bengalensis and M. scabra was 19% and 10% on stone and 52% and 80% on sand respectively. In the absence of food from both stone and sand and also when sand alone was baited, both snails flocked principally towards sand. When stone alone was provided with food, V. bengalensis and M. scabra displayed 16% and 15% distribution on stone and 49% and 45% on sand respectively. Ecological significance of these results is discussed.