Studies on molluscan diversity in Kaveri river system (Tiruchirappalli, India) with special reference to vector snails of trematode parasites

A monthly collection of molluscan animals was carried out from 11 sampling stations (K1–K11) of Kaveri river stretch from Karur to Grand Anicut (95 km) for a period of two years (April 1991–March 1993). 13 species of molluscs were recorded, of which 8 species were gastropods and 5 species bivalves. The gastropod species were grouped under 5 different families (Viviparidae, Thiaridae, Pilidae, Lymnaeidae and Planorbidae) and the family Thiaridae was the most dominant group representing 50% of the total gastropod population. Five species of bivalve molluscs were classed under 2 different families namely Unionidae and Corbiculidae. The mean density of molluscs was higher (96/m2) in sector I (K1–K4) than in sector II (39/m2) which include stations K5–K11. Five gastropod species were identified as carriers of the disease causing parasite cercarial larvae. The pulmonate snails were preferred most by trematode cercaria.