THE FRESH-WATER SNAIL BULINUS-TROPICUS (PLANORBIDAE) IN NAMIBIA, CHARACTERIZED ACCORDING TO CHROMOSOME-NUMBER, ENZYMES AND MORPHOLOGY

Freshwater snails collected in central Namibia, south-western Africa, from 15 populations belonging to the Bulinus truncatrcs/tropicus compl ex (Planorbidae) are characterised in respect of their chromosome numb er, morphology, egg proteins and enzymes. The population samples were all consistently diploid and euphallic. The findings are compared with observations on this group of snails in other areas of Africa. It is concluded that the Namibian populations belong to a single species, B. tropicus (Krauss, 1848), of which B. parietalis (Mousson, 1887) is pr obably a synonym. No evidence was found of any occurrence of the tetra ploid species B. truncatus or of snails belonging to the B. africanus group; lack of a potential intermediate host therefore precludes trans mission of Schistosoma haematobium in this area.