Hidden Diversity in Eigenmannia (Gymnotiformes: Sternopygidae) Populations from Upper Paraná and Paraguay Rivers.

Eigenmannia is a highly diverse genus within the Sternopygidae family, comprising 30 species. Due to its complex taxonomy, molecular analyses have been crucial for species delimitation within this group. Therefore, the present study presents a genetic analysis using sequences of the mitochondrial gene cytochrome c oxidase subunit 1 (COI) in specimens previously identified through alpha taxonomy as E. correntes (with unpublished data), E. virescens, and E. trilineata, originating from various locations within the Upper Paraná and Paraguay River basins in Brazil. The molecular data confirm the taxonomic complexity of the genus, as individuals morphologically identified as E. virescens and E. trilineata shared the same haplotype (H52). Furthermore, the results of the species delimitation tests suggest that specimens morphologically identified as E. virescens belong to the species E. trilineata. In addition, samples morphologically identified as E. correntes may correspond to more than one Operational Taxonomic Units (OTUs). Furthermore, the intraspecific Kimura-2-parameter (K2P) distances within the different studied populations are significant. This study has contributed valuable information about genetic diversity in Eigenmannia, emphasizing the importance of using integrative analyses to resolve taxonomic conflicts within the group. It also supports biogeographical studies and assists in biodiversity conservation efforts.

Identification and molecular characterization of digenean trematode parasites of Aylacostoma chloroticum (Gastropoda: Thiaridae) from a Neotropical Basin.

Thiarids are pantropical gastropods distributed from South America to Australia and found in lentic and lotic freshwater environments. These gastropods act as intermediate hosts for several species of digeneans. There are difficulties in the correct identification of these digeneans in certain stages of the life cycle as the larvae have a reduced size and few morphological characteristics for diagnosis. Because of this, techniques based on molecular markers have become an extremely useful tool. Our objective was to molecularly characterize the digeneans found in gastropods from the Ivaí River, Paraná, Brazil, using the mitochondrial molecular marker cytochrome c oxidase (COI) and the 28S ribosomal marker. With the molecular marker COI, gastropods showed high genetic similarity with Aylacostoma chloroticum. For the parasites, four different taxa were characterized with both markers. The 28S ribosomal marker proved to be more effective for the identification of Ivaí River parasites, being possible to suggest the identification of two species among the four groups found. Considering that there are no records in the literature of studies involving parasites and gastropods as intermediate hosts in the Ivaí River, this study is the first regarding these relationships.

Molecular evidence of new freshwater turtle blood flukes (Digenea: Spirorchiidae) in the intermediate snail host Biomphalaria occidentalis Paraense, 1981 in an urban aquatic ecosystem in Brazil.

In this study, two potentially new species of turtle blood flukes (TBFs) (Digenea: Spirorchiidae) have been recorded from South Brazil. The spirorchiid parasites infect the vascular system of turtles, thereby compromising their health. The life cycle of these parasites is not well studied. The larval stage of cercaria is found in intermediate gastropod hosts, with some species presenting similar morphological characteristics, which can result in misinterpretations when using only morphological taxonomy for species identification. In this study, we recorded a single morphotype belonging to the family Spirorchiidae in Biomphalaria occidentalis in an urban aquatic ecosystem in Brazil. However, molecular data (28S rDNA and cytochrome oxidase subunit I) confirmed the presence of two species of Spirorchiidae in the sampled environment; both phylogenetically close to genera previously studied in freshwater turtles from the Peruvian Amazon. In this study, species characterization was possible because of molecular tools. We recommend using more than one molecular marker in future studies focusing on TBFs, which need attention about their evolutionary history and ecology to understand their distribution in South America.