The Potamotrygonidae is the family inside Chondrichthyes class exclusively from freshwater and are distributed in the most river basins that have drainage to the Atlantic Ocean, such as Amazônas-Orinoco, Paraguay-Paraná, Uruguay and Parnaíba river basins. The Myxozoa are obligatory cnidarian parasites divided into two classes: Malacosporea and Myxosporea. More than 2400 species are included in Myxosporea, the majority are fishes parasites inhabiting freshwater and marine environments. However, there are only a few studies on myxosporeans of cartilaginous fishes in the world, aproximately 130 reports worldwide. The taxonomy of the Myxozoa is traditionally made through morphological and molecular approaches. Molecular phylogenetic studies for this parasite group broadly use the ribosomal genes, especially the SSU rDNA (18S), and sometimes these genes present incipient results regarding the resolution of deep relationships within this group. Thereby there is an urgent need to test new approaches, e.g. phylogenomic using Ultraconserved Elements (UCEs). Ultraconserved elements have been widely used in systematics and phylogeography studies on vertebrates, and recently invertebrates, and the results have shown the opportunity to access subgenomics datasets capable of providing higher resolution to phylogenies different from the phylogenies with low quantity of markers from the Sanger methodology. Our primary goal is to study the systematic, biodiversity and distribution of myxosporeans sampled in freshwater stingrays of Potamotrygonidae family captured in the rivers Tapajós/Amazonas in the municipality of Santarém, State of Pará, Parnaíba river in the municipality of Teresina, State of Piauí and Miranda river, in the municipality of Corumbá, State of Mato Grosso do Sul. The studies will be held using morphological taxonomy with light and electronic microscopy, molecular approaches using traditional ribosomal markers (18S and ITS) and as an innovative approach, using the next generation sequencing with UCEs. The sequencing results will be used in phylogenetic inferences aiming to establish the relationships among myxosporeans from Potamotrygonidae with lineages from other elasmobranchs in a general evolutionary context of the group.
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