Origin and evolution of alternative developmental strategies in amphibious sarcopterygian parasites (Platyhelminthes, Monogenea, Polystomatidae)

摘要: Most integrative studies involving phylogenetic, developmental and ecological trends showed that the diversity of modifications among Platyhelminthes was linked to transmission opportunity pressures. For parasitic flatworms with complex life cycles it suggested evolutionary forces constrained or enhanced strategies implied heterochronic patterns. Similar patterns were also reported from Monogenea direct cycles, especially for Polystomatidae, which infest amphibious Sarcopterygians. Polystoma, whose members are recovered almost exclusively anuran hosts Neobatrachia, is capable following two alternative depending on physiological stage its host. Processes by parasites reach maturity strikingly different, lead discrete adult phenotypes within same parasite species. In present study, we investigate origin evolution polystomatids in a phylogenetic framework, using an approach heterochrony ecology. The results suggest both have coexisted during early stages polystome evolution, neither them can be considered as ancestral one. pathways, each associated one cycle, may arisen independently prior diversification, when strictly aquatic sarcopterygians attempted colonization temporary freshwater environments. occurrence these species genus Polystoma reflect condition, allowed successful shifts opportunities. Thus, host ecology main factor shaping polystomatids.