Cercarial productivity of Fasciola hepatica in Lymnaea truncatula during usual and unusual development of redial generations.

Single-miracidium infections of Lymnaea truncatula by Fasciola hepatica were carried out to determine the cercarial productivity of each redial generation when the first-appearing mother redia (R1a redia) normally developed (usual development of redial generations) or quickly died (unusual development). In both developmental patterns of infection, the number of morulae was significantly higher in the second-appearing mother rediae (R1b group) than in either the daughter rediae from R1a rediae (R2a group) or the rediae from subsequent groups (R2b/R3a). The live R1a group did not produce cercariae. The percentages of cercariae produced by the R1b, R2a, and R2b/R3a groups were 28.2%, 62.8%, and 8.9% when the development of redial generations was usual. In contrast, in an unusual development, they were 69.3%, 20.3%, and 10.2%, respectively. Cercarial production until day 63 post-exposure was essentially provided by the R2a rediae, when the development of redial generations was usual, and by the R1b rediae when it was unusual.