Identification of sex of schistosome larval stages.

Sex of Schistosoma mansoni cercariae was identified by a C-banding technique; interphase nuclei of females exhibited W-chromatin (heterochromatin of the W chromosome) whereas those of males did not. Similar sexual dimorphism was also shown in nuclei of S. mansoni miracidia, sporocysts, and adult worms. Cercariae of the following schistosomes could not be sexed by examination of nuclei after the C-band technique: S. japonicum, S. haematobium, and Schistosomatium douthitti . The method presented was 100% accurate and relatively rapid (total time for S. mansoni cercariae: 80 min).