A synthesis of the ichthyofauna of the headwaters of the rio Tietê, based on material from zoological collections and new samplings, is presented. Fifty six species belonging to seven orders and 16 families are recorded to the drainage, increasing previous numbers significantly. The current results show that the headwaters of the rio Tietê possess a singular ichthyofauna composition, diverse from that found in the remaining of the upper Paraná basin, with high level of endemic species and great similarity to the species from coastal drainages. This finding corroborates the hypothesis of past river capture between streams and rivers in both drainages. Among the species occurring in the area surveyed, eight are endemic (14.3%), 13 are found in the headwaters of rio Tietê and in the coastal drainages of southeastern Brazil (23.2%), 10 are present throughout the upper Paraná basin (17.9%), five are found in the upper Paraná basin and in the coastal drainages of southeastern Brazil (8.9%), while 13 show a broader distribution in the South America drainages (23.2%), part of which still remains to be identified. Species diversity increased with the discovery of at least five new species belonging to the genera Cyphocharax, Characidium, Astyanax, Pareiorhina and Australoheros, and four new records for Characidium cf. zebra, Scleromystax barbatus, Crenicicla britskii and Synbranchus cf. marmoratus. At least, seven non-native species are recognized to be established in the region, while 10 other are included in red books.
biodiversity; new species; new records; identification key; conservation
