Praziquantel (PZQ) is effective against all the evolutive phases of Schistosoma mansoni. Infected Biomphalaria
glabrata snails have their cercarial shedding interrupted when exposed to PZQ. Using primary in vitro transformed
sporocysts, labeled with the probe Hoechst 33258 (indicator of membrane integrity), and lectin of Glycine max
(specific for carbohydrate of N-acetylgalactosamine membrane), we evaluated the presence of lysosomes at this
evolutive phase of S. mansoni, as well as the influence of PZQ on these acidic organelles and on the tegument of the
sporocyst. Although the sporocyst remained alive, it was observed that there was a marked contraction of its
musculature, and there occurred a change in the parasite’s structure. Also, the acidic vesicles found in the sporo-
cysts showed a larger delimited area after contact of the parasites with PZQ. Damages to the tegument was also
observed, as show a well-marked labeling either with Hoechst 33258 or with lectin of Glycine max after contact of
sporocysts with the drug. These results could partially explain the interruption/reduction mechanism of cercarial
shedding in snails exposed to PZQ.