More efficient allopatric combinations of Fasciola hepatica and Lymnaea truncatula due to modification of redial development?

Experimental infections of two susceptible French populations of Lymnaea tr uncatula (Courcelles and Saint Ours) with an allopatric (Fes, Morocco) or a semi-sympatric (Limoges, France) isolate of Fasciola hepatica miracidia we re performed to determine the effect of allopatric miracidia on redial and cercarial production. In both populations, cercarial release was significan tly greater in allopatric than in semi-sympatric snails. Compared to semi-s ympatric snails, the examination of allopatric snails killed from day 14 to day 35 post-exposure demonstrated (1) a significant decrease after day 28 in the number of daughter rediae (R2a group) exiting from the first-appeari ng mother redia (R1a redia), and (2) the differentiation of numerous daught er rediae (R2b group) in the body of second-appearing mother rediae (R1b gr oup). These experiments demonstrated that the exposure of L. truncatula to an allopatric isolate of miracidia disturbed the usual developmental patter n of redial generations and caused the formation of numerous R2b rediae. Th e authors hypothesized that the increase in cercarial release noted in allo patric snails would be assured by the rediae from the R2b group after their emergence from the body of R1b mother rediae.