New insights into Ituglanis (Siluriformes: Trichomycteridae) diversity in Bahia State, eastern Brazil: Description of a new species and conservation status reappraisal.

The northeastern Atlantic Forest of Brazil harbours a remarkable diversity of species of Trichomycteridae, many of which remain poorly understood. This study describes a new species of Ituglanis, endemic to the Ribeirão São Roque, a stream tributary of Rio Piabanha, an affluent of Rio Colônia basin, Bahia State, Brazil. The new species is distinguished from its congeners by a combination of the following characters: four pairs of ribs; 35 post-Weberian vertebrae, seven pectoral-fin rays; and a colour pattern consisting of irregular dark brown spots along the flanks and dorsal region. The specimens were encountered during field studies conducted in southern Bahia State aimed at collecting Ituglanis cahyensis and Ituglanis agreste. However, despite extensive efforts, neither of these species was found during surveys, suggesting potential population declines. Additionally, we reassess the conservation status of the species of Ituglanis from Bahia State, proposing status updates for three of the four previously described species based on recent field data and habitat assessments. The discovery of this new species underscores the urgent need for further exploration and collection in poorly sampled areas of the Atlantic Forest. Human activities, including deforestation and habitat degradation, continue to threaten these unique ecosystems. As demonstrated here, the description of new species contributes not only to a better understanding of biodiversity and evolutionary relationships within Ituglanis but also to conservation efforts in one of the most endangered biodiversity hotspots in the world.