Caracterização Morfológica de Duas Espécies Novas do Gênero Pseudacanthicus Bleeker (Siluriformes, Loricariidae) das Bacias dos Rios Tapajós e Curuá-Una

Abstract

Pseudacanthicus is a genus allocated within the family Loricariidae and which currently has eight formally described species distributed in several basins of northern South America: P. serratus, P. fordii, P. spinosus, P. histrix, P. leopardus, P. pitanga, P. pirarara, and P. major. The present work aimed to describe two new species of Pseudacanthicus, in addition to delimiting the geographic distribution of both and developing an identification key for the genus. The description was based on morphology, mainly of external characteristics, where meristic and morphometric data were taken so that these measurements were put in proportion and compared with the material of the species already described, also considering osteology and coloration patterns for the diagnosis. Pseudacanthicus sp. “Curuá-Una”, occurs in the basins of the Curuá-Una and Tapajós rivers, and differs from the other species of the genus, except for Pseudacanthicus sp. “Jamaxim”, because it has a color pattern with a dark background superimposed by white dots distributed throughout the body (vs. gray to dark brown body with black dots or spots in P. spinosus and P. histrix, no spots and white bands on dorsal and caudal fins in P. major; presence of orange fins in P. leopardos, P. pitanga and P. pirarara, with black background and white dots concentrated in the ventral region in P. serratus and P. fordii), Pseudacanthicus sp. “Curuá-Una” differs from Pseudacanthicus sp. “Jamanxim” for never having light spots forming irregular spots or yellow bars on the dorsal and caudal fins (vs. color pattern with dark background superimposed by irregular white or yellow dots, which can form spots, also having yellow bars on the dorsal and caudal fins). Pseudacanthicus sp. “Jamanxim”, occurs in the Jamanxim river, a tributary of the Tapajós basin, and differs from the other species of the genus by having a color pattern with a dark background superimposed by irregular white or yellow dots, which can form spots, also having yellow bars on the dorsal and caudal fins. This study is an addition to the knowledge about the genus and biodiversity of fish, considering that there are still several species to be described and the diversity of the ichthyofauna is still very underestimated.