In this study, we analyzed the genetic variability of D-loop sequences in different species of the genus Steindachneridion. Genetic variability in the species of Steindachneridion Garavello, 2005 (Siluriformes: Pimelodidae)

The genus Steindachneridion, which includes large-sized freshwater pimelodid species, is endemic to the southeastern coastal drainages of South America, specifically the Paraná River and Uruguay River basins. In this study, genetic analyses of mitochondrial DNA (mtDNA) D-loop were conducted on four species within this genus across their respective distributions: Steindachneridion scriptum (from the Tibagi and Uruguay Rivers), S. melanodermatum (from the Iguaçu River), S. doceanum (from the Doce River), and S. parahybae (from the Paraíba do Sul River). Zungaro zungaro and Brachyplatystoma rousseauxii were employed as outgroups, and the topology was inferred using Bayesian Inference (BI) and Maximum Likelihood (ML) phylogenetic reconstruction techniques. Additionally, the sequences were analyzed to assess genetic diversity levels.