Presence of Corydoras paleatus (Jenyns, 1842), a new Brazilic species in the north of Patagonia (Limay River), and ecological aspects related to its distribution

Finding of Corydoras paleatus is reported in a secondary branch of the Limay River; it represents a zoogeographic novelty for the northern Argentine Patagonia (Neuquen y Río Negro provinces). This species was captured by electrofishing in a large pool characterized by dense submerged macrophytes. The presence of Corydoras paleatus in the Limay River extends the southern geographical boundary outside the Pampean plain, where the species inhabits warm temperate rivers and lakes of the Salado River basin as well as cold streams belonging to the Sierra de la Ventana watershed. With the discovery of Corydoras paleatus, the Brazilic ichthyofauna represents 30 percent of total species richness for all Patagonia, and the discovery increases up to eight the number of such species inhabiting the northern boundary of this region. This area encompasses a wide ecotone, delimited by Colorado and Negro rivers, where the distribution of Brazilic species is still not well known. Although some species such as Corydoras paleatus, Odontesthes bonariensis and Jenynsia multidentata appear to be ubiquitous and to have the potential to extend their geographical distribution, the ability of Brazilic species for the colonization of Patagonian environments may be related to the tolerance to minimum temperature and maximum salinity levels, as well as to the presence of suitable local conditions