Abstract
Accurate identification of the freshwater snails that are responsible for schistosome transmission is needed in order to settle the best control strategy. We propose herein a description of the anatomical characters that allow distinguishing between the three planorbids snails: Biomphalaria pfeifferi, the main intermediate host of Schistosoma mansoni in Africa, Helisoma duryi and Indoplanorbis exustus. B. pfeifferi has a few prostatic diverticulae arranged in a row; the penis sheath is narrower and a little smaller than the preputium. H. duryi has a few prostatic diverticulae branched repeatedly giving the organ a cauliflower-like appearance; the penis sheath is pear-shaped and the preputium shows a characteristic lateral swelling produced by a preputial organ. In I. exustus, the prostatic diverticulae are arranged in a compact fan-shaped organ. The penial complex lacks the conspicuous preputial organ of H. duryi; it is of the bulinid type with a penis sheath four times longer than the preputium