The species Corydoras paleatus (Jenyns, 1842) is widely distributed in Southern Brazil, occurring from Rio Grande do Sul to the north of Paraná State. Studies related to this species populations are considered important once this fish is distributed in a region with great anthropogenic interference and also because its economic importance, given that this species is commercialised as ornamental fish. In the present study sixteen morphometric characters and six meristic characters were used for morphological evaluation in populations of Tibagi and Iguaçu river basins (Paraná) and Lagoa dos Quadros (Rio Grande do Sul). In spite of the number of lateral plates being more variable in specimens from Iguaçu river, the overlap of plates and fin rays counts did not allow a safe discrimination of populations. However, principal components analysis allowed to differentiate populations by the allometric growth of the morphometric characters. Besides, the sample from rio Iguaçu was morphometrically discriminated of those from Tibagi river and Lagoa dos Quadros in the first canonical axis, while these two populations were separated in the second axis. The intraspecific variation, observed in this species, clearly shows that population morphometric analysis can be useful in the analysis of biological diversity of a given region. The morphometric differences and the geographical isolation are indicating that those populations are subject to different selective processes.
Allometry; biological diversity; multivariate morphometric; Neotropical fishes; small catfishes
