O gênero Echinostoma Rudolphi, 1809 (Trematoda: Echinostomatidae) no Brasil: estudo taxonômico integrativo de algumas espécies encontradas em Minas Gerais

Abstract

Species of the genus Echinostoma are digeneic trematodes that parasitize, as adults, the digestive system of birds and mammals, including humans. These parasites have a cosmopolitan distribution and more than 100 described species, although the taxonomy of the group is quite complex and controversial. Integrative taxonomic studies carried out over the last few decades have revealed and provided more robust hypotheses regarding the validity of the taxa, improving the understanding of the real diversity of the group and even the occurrence of cryptic species in this genus. However, the scenario involving Echinostoma spp. that occur in Brazil is still unclear, considering that despite the high nominal species richness (about 30 species), molecular data for these species are practically non-existent. The main objective of this study was to combine morphological and molecular data (nuclear genes: 28S and ITS; mitochondrial: cox1 and nad1) from samples of Echinostoma spp. obtained from vertebrate and invertebrate hosts from localities in the state of Minas Gerais, Brazil. For this, adult specimens obtained from experimentally or naturally infected vertebrates were used for morphological descriptions and comparisons from permanent mounts on slides. DNA samples from one adult worm of each species studied were used for phylogenetic analyses. The results obtained in this integrative taxonomic study allowed the description of two new species and the molecular sequences of two other species of Echinostoma already known, allowed exploring their phylogenetic relationships. Molecular analyzes of the first species described from naturally infected free-range hen adult worms in the municipality of Viçosa, Echinostoma pseudorobustum, revealed co-specificity with cercariae previously reported as E. robustum and supported a discussion on closely related species in the New World. Adult parasites obtained experimentally from larval stages found in the mollusc S. marmorata naturally infected in the municipality of Alvorada de Minas and phylogenetic reconstructions based on four DNA loci (28S, ITS, cox1, nad1) allowed the discovery of a second new species of Echinostoma morphologically similar to E. paraensei, but genetically distinct, called Echinostoma maldonadoi. The third species studied, obtained through experimental infection in canary and pigeon, corresponded well to the morphological description of E. nephrocystis and molecular analyzes demonstrated proximity with the African species E. caproni, suggesting a possible ancestry between these species. Finally, for the molecular characterization of E. exile, a species already known in Brazil, a multigenic approach (28S, ITS and nad1) evaluated the phylogenetic position of the species and, the data obtained did not support the maintenance of the species in the genus Echinostoma, being requested its transfer to the genus Echinoparyphium, with amendment in the diagnosis. Integrative taxonomic approaches are essential to clarify aspects of the diversity of Echinostoma species that occur in Brazil and to illuminate the phylogenetic relationships between them.