International audienceThe Platyhelminths, or flatworms, are represented by several thousands of species. This phylum consist of several groups, including the Monogeneans. Principally ectoparasites of aquatic vertebrates, these organisms have been studied since the nineteenth century, but essentially from the taxonomic point of view. The study of their population dynamics stay marginal, despite the ecological or epidemiological interest of this zoological group. The demographical modelling is rare and concern only some Monopisthocotylea, ectoparasites of Teleosteans. The main biomathematical trends are summarized in this paper ; their interest is underlined, but also some of their more serious weaknesses. Using the sea bass (Dicentrarchus la...