 |
| Pseudacanthicus nyktos Lopes, Sousa & Chamon, 2024 |
Abstract
The genus Pseudacanthicus encompasses eight recognized species so far: P. histrix, P. serratus, P. spinosus, P. fordii, P. leopardus, P. pitanga, P. pirarara, P. major. Only P. pirarara has been formally described from the rio Xingu basin. To address this gap in taxonomic knowledge of the region, a new species of the Pseudacanthicus is described here, aimed at enhancing our understanding of the genus within the rio Xingu basin and contributing to conservation efforts. The new species is primarily found downstream the impact zone of the Belo Monte Hydroelectric Power Plant. It can be promptly diagnosed from congeners by the color pattern of the body dark brown to black with light gray vermicular spots on the dorsal and ventral surfaces, and fins; lower maximum number of teeth in premaxilla and dentary; and other osteological characters. It’s worth noting that the ichthyofauna of the Amazonian drainages lacks comprehensive taxonomic and biological information regarding Pseudacanthicus. In this context, unchecked anthropogenic activities are leading to changes in the ecosystem, often resulting in the extinction of species even before they are scientifically addressed.
Keywords: Acanthicus clade; Amazon basin; Ancistrini; Conservation; Taxonomy
 |
| Holotype of Pseudacanthicus nyktos, INPA-ICT 060701, 190.18 mm SL, rio Xingu, Vitória do Xingu. A. Dorsal view; B. Lateral view; C. Ventral view. |
 |
| Ventral view of mouth and barbels of Pseudacanthicus nyktos. Specimen not preserved. Premaxillary and dentary teeth of a skeletonized paratype of Pseudacanthicus nyktos (LIA 8173, 154 mm SL). |
Pseudacanthicus nyktos, new species
Diagnosis: Pseudacanthicus nyktos differs from all congeners by a dark brown to black body with light gray vermicular spots on the dorsal and ventral surfaces, and fins (vs. body with dark gray to dark brown background with black dots or spots and fins with intense orange to red color in P. leopardus, P. pitanga and P. pirarara; body and fins with dark gray background color and white dots or spots in P. serratus and P. fordii, more conspicuous in ventral region; body with a gray color and black dots or spots in P. histrix and P. spinosus; and body with a dark brown color without spots or dots; with white transverse bars on the dorsal and caudal fins ...
Etymology: The specific epithet nyktos derives from Greek meaning “night”, in allusion to the dark color of the specimens in comparison with other species of the genus and also to the deep locations where they can be found, where there is no light. An adjective.
 |
| Body shape and color in life of Pseudacanthicus nyktos shown to scale. Specimens not preserved. Scale bars = 1 cm. |
Maria Letícia Batista Galvão Lopes, Leandro Melo de Sousa and Carine Cavalcante Chamon. 2024. New Species of Pseudacanthicus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil. Neotrop. ichthyol. 22(3) • 2024 • DOI: 10.1590/1982-0224-2024-0033 www.scielo.br/j/ni/a/XHfLffzyJxq445HxZs4bnkF
