Anatomical characters for easy identification between Biomphalaria pfeifferi, Helisoma duryi and Indoplanorbis exustus during field surveys

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.