Abstract
An increasing number of studies underlines the need to consider parasitism as an important component of ecosystem functioning. In this paper, we review the multi-effects of the trematode Microphallus papillorobustus in the salt marshes of Southern France. We describe the effects of this parasite on the behaviour, fecundity, growth and survival of its hosts, as well as its consequences on host sexual selection and finally, its role in maintaining biodiversity. In the light of this review, we suggest that this parasite should be considered as an important species to understand the functioning of lagunar ecosystems.