[Redial generations of Fasciola hepatica L. in Lymnaea truncatula Müller apropos of the effects of several factors].

There was a succession of 3 redial generations in 4-mm-high snails individually exposed to a single miracidium and then bred at 20 degrees C during 30 days after exposure. The geographic strain of miracidia of Fasciola hepatica had no influence on the development of these redial generations. The succession of these redial generations changed in the case of plurimiracidial exposures. In snails once exposed to high numbers of miracidia (from 5 to 20), the mean number of rediae per snail decreased affecting especially the generations 2 and 3; the maturation of rediae of generations 1 and 2 was later when the number of used miracidia was higher. The same results were found in snails individually subjected to 4 exposures with one miracidium per exposure. The significance of these observations is discussed.