Fine-scale habitat associations of soft-sediment gastropods at Cape Maclear, Lake Malawi

摘要

Lake Malawi harbours a high diversity of gastropod species, yet little is known of their distributions or habitat affiliations. We conducted a study of the gastropods present on soft sediments at five sites around Cape Maclear, in the south of the lake. The two most common taxa were Bulinus nyassanus, a known vector for Schistosoma haematobium and Melanoides. Both were found to be in much higher abundance than ever previously recorded. Densities of these gastropods were highly dependent upon habitat characteristics including depth, sediment particle size and sediment organic content. Together these factors explained 49 and 70% of variance in B. nyassanus and Melanoides abundance, respectively. There were no significant differences between the five sites after accounting for habitat variables. These data indicate that habitat characteristics are substantially important in determining the geographic differences in gastropod abundance, thus we propose that nearshore habitat variables may be strongly linked to schistosomiasis prevalence among lakeshore human populations.