OBSERVATIONS ON THE ECOLOGY OF BULINUS (PHYSOPSIS) GLOBOSUS (MORELET), B. (BULINUS) FORSKALII (EHRENBERG) AND LYMNAEA NATALENSIS (KRAUSS) IN RICE SWAMPS IN SIERRA LEONE.

Changes in population of Bulinus globosus, B. forskalii andLymnaea natalensis were studied in four different locationsnamed Sites A, B, C. and D in Bo town Sierra Leone. The snailpopulations and oxygen concentrations of water increased inthe rainy season. The biological oxygen demand did not havesignificant correlation with changes in snail populations inSites B and D. B. globosus was absent from Site A while B. forskaliiwas the predominant snail in Site C. Site D with the highestmean monthly conductivity of 176 µmhos contained 54% whileSite A with a similar reading of 90µmhos contained 1%of all snails found. (Received 22 May 1980;