In myxohaline environments, the digenean Maritrema bonaerense shares intermediate host species (crustaceans) and a definitive host species (bird) with another member of the family Microphallidae: Microphallus szidati. However, only M. szidati has been recorded parasitizing intermediate hosts in freshwater environments. Given that both species of microphallids would have affinity for the same host species in marine or mixohaline environments, it is possible that the absence of M. bonaerense in freshwater environments is mainly due to an environmental barrier that may affect the transmission of the free-swimming stages of the digenean (cercariae). Based on these considerations, the objective of this study was to analyze the effect of salinity on the survival of cercariae of M. bonaerense. For this, cercariae emitted by Heleobia australis from myxohaline environments were exposed to salinities of 16 ppm and 1 ppm in culture plates with 48 wells of 16 ml capacity. For 10 hours plates were observed every hour under a stereomicroscope and the number of live cercariae in each compartment was recorded. 24 hours after the experiment began, plates were observed, recording the total number of live cercariae, which were classified as active cercariae, lethargic cercariae, and lethargic cercariae that lost their tails. The effect of salinity on the survival of cercariae was analyzed by applying Generalized Linear Models (GLM). The results of the study revealed a marked influence of salinity levels on the survival and mobility of cercariae, and allow us to assume that M. bonaerense is a species better adapted to marine and mixohaline environments.