Population dynamics and ecology of freshwater gastropods in the highveld and lowveld regions of Zimbabwe, with emphasis on schistosome and amphistome intermediate hosts

Abstract

From November 1998 to October 2000, patterns of distribution and seasonal population fluctuations of snails and factors influencing them were investigated in six dams and six streams in the highveld region, and in nine dams in the lowveld region of Zimbabwe. At monthly intervals, each site was sampled for relative snail density, vegetation cover and physical and chemical properties of the water. Bulinus globosus, B. tropicus, B. forskalii, Biomphalaria pfeifferi, Lymnaea natalensis, Ceratophallus natalensis, Gyraulus costulatus, Melanoides tuberculata, Bellamya capillata and Lanistes ovum were the snail species recorded from the study sites. The seasonal trends of the species were variable but generally counts peaked during or shortly after the rainy period. Ecological factors did not markedly influence the observed numerical trends of the snail populations.