RESUMO
A new miniature species of Hyphessobrycon is described from an affluent of the Rio Papagaio, tributary of the Rio Juruena, upper Rio Tapajós basin, Mato Grosso State, Brazil. The new species can be distinguished from its congeners by having a remarkable secondary sexual dimorphism in its live colouration (males are red and females yellow), well-defined and relatively narrow dark midlateral stripe extending from tip of snout to tip of middle caudal-fin rays, absence of humeral blotch, 15-18 branched anal-fin rays and five or six branched pelvic-fin rays. The sexually dimorphic colouration of the new species is briefly discussed regarding its temporal variation.
Assuntos
Characidae/anatomia & histologia , Caracteres Sexuais , Animais , Brasil , Feminino , Masculino , Pigmentação , RiosRESUMO
Hyphessobrycon myrmex sp. nov., is described from the Rio Formiga, upper Rio Juruena, upper Rio Tapajós basin, Mato Grosso, Brazil. The new species can be distinguished from congeners by having the lower half of the body deeply pigmented with dark chromatophores, chromatophores concentrated above the anal fin and forming a broad, diffuse, dark midlateral stripe and by having a dense concentration of dark chromatophores along unbranched dorsal-fin rays and distal portions of the two or three subsequent branched rays. In life, H. myrmex exhibits a conspicuous sexual dichromatism, with adult males red to orange and females and immatures pale yellow. A list containing 108 sexually dichromatic taxa in six families of Characiformes is provided and the distribution of this poorly known type of dimorphism across the Characiformes is discussed.
Assuntos
Characidae/anatomia & histologia , Animais , Brasil , Characidae/classificação , Cor , Feminino , Masculino , Rios , Caracteres Sexuais , Especificidade da EspécieRESUMO
A new species of Hyphessobrycon is described from a tributary of the upper Rio Tapajós, Amazon basin, Mato Grosso, Brazil. Its exuberant colour in life, with blue to purple body and red fins, is appreciated in the aquarium trade. Characters to diagnose the new species from all congeners are the presence of a single humeral blotch, absence of a distinct caudal-peduncle blotch, absence of a well-defined dark mid-lateral stripe on body, the presence of 16-18 branched anal-fin rays, nine branched dorsal-fin rays and six branched pelvic-fin rays. A brief comment on fish species descriptions solely based on aquarium material and its consequence for conservation policies is provided.