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The Diplostomidae is a globally distributed family of digeneans that parasitize a wide variety of tetrapod definitive hosts. Recent molecular phylogenetic studies have revealed unknown diplostomid diversity in avian hosts throughout the New World. Herein, we provide descriptions of a novel genus of diplostomids with two new species.Two species of diplostomids belonging to the new genus were collected from anhinga birds in Mississippi (USA) and Brazil. Partial nuclear 28S ribosomal and mitochondrial cox1 genes were sequenced. Ribosomal data were used for phylogenetic inference.Both species of Anhingatrema n. gen. were positioned in a 100% supported, monophyletic clade in the phylogenetic tree. The molecular phylogenetic position and a combination of morphological features (e.g., presence of pseudosuckers, testes shape and orientation) supported erection of the new genus. Anhingatrema overstreeti n. sp. and Anhingatrema cararai n. sp. are morphologically similar, but differ in size of and ratios associated with pseudosuckers. The two species differ by 2% of 28S sequences and 13.8% of cox1 sequences. Comparison of DNA sequences revealed that Diplostomidae gen. sp. in GenBank (MZ314151) is conspecific with An. overstreeti n. sp.Anhingatrema n. gen. is the sixth genus of diplostomids known from anhingas worldwide. Anhingatrema cararai n. sp. is the first diplostomid to be reported from anhingas in South America. Combined with previous studies, the molecular phylogenies revealed at least two host switches to anhingas from other birds during the evolutionary history of the Diplostomidae.

Species that are introduced to novel environments can lose their native pathogens and parasites during the process of introduction. The escape from the negative effects associated with these natural enemies is commonly employed as an explanation for the success and expansion of invasive species, which is termed the enemy release hypothesis (ERH). In this study, nested PCR techniques and microscopy were used to determine the prevalence and intensity (respectively) of Plasmodium spp. and Haemoproteus spp. in introduced house sparrows and native urban birds of central Brazil. Generalized linear mixed models were fitted by Laplace approximation considering a binomial error distribution and logit link function. Location and species were considered as random effects and species categorization (native or non-indigenous) as fixed effects. We found that native birds from Brazil presented significantly higher parasite prevalence in accordance with the ERH. We also compared our data with the literature, and found that house sparrows native to Europe exhibited significantly higher parasite prevalence than introduced house sparrows from Brazil, which also supports the ERH. Therefore, it is possible that house sparrows from Brazil might have experienced a parasitic release during the process of introduction, which might also be related to a demographic release (e.g. release from the negative effects of parasites on host population dynamics).