RESUMO
Infection of hermaphroditic freshwater snails with digenetic trematodes causes a strong reduction in gamete production and sexual maturation. The reduction in gamete production in infected snails coincides with the migration and establishment of larval stages of parasite in the gonad acini. The acini were abserved to be invaded with large numbers of rediae and cercariae and consequently the gonad of B, alexandrina [Ehrenberg, 1831] and B. truncatus [Audouin, 1827] following exposure to infection were investigated, to characterize the parasite-induced response and to understand its functional relevance. Infection provoked significant elevations in titres, but this elevation doesn't interfere or stop the fate of parasite. Thus, the functional relevance of the response remains enigmatic