Hemigrammus ataktos: a new species from the rio Tocantins basin, central Brazil (Characiformes: Characidae)

Abstract

A new species of Hemigrammus is described from the middle rio Tocantins basin, central Brazil. The new species can be distinguished from all congeners by having a black midlateral stripe on the body extending from the posterior margin of the eye to the median caudal-fin rays. Mature males possess dorsal-, pelvic-, and anal-fin rays elongate, features that also help to recognize the new species. Although the new species is described in Hemigrammus, some specimens present a complete series of pored scales in the lateral line. A discussion about the generic allocation of the new species is presented. Uma espécie nova de Hemigrammus é descrita da bacia do médio rio Tocantins, Brasil central. A espécie nova distingue-se de seus congêneres por apresentar uma faixa mediana negra na lateral do corpo desde a margem posterior do olho até os raios medianos da nadadeira caudal. Machos maduros apresentam os raios das nadadeiras dorsal, pélvica e anal alongados, características que também auxiliam o reconhecimento da espécie. Apesar da espécie nova ser descrita em Hemigrammus, alguns exemplares possuem série completa de escamas perfuradas na linha lateral. Uma discussão sobre o posicionamento genérico da espécie nova é apresentada.

A new species of Moenkhausia Eigenmann (Characiformes: Characidae) from the upper rio Machado at Chapada dos Parecis, rio Madeira basin, Brazil

“…These characters were found subsequently to be highly homoplastic within the Characidae (Weitzman & Fink, 1983;Mirande, 2010;Marinho et al, 2014;Dagosta et al, 2014). As a consequence, Eigenmann's classification scheme resulted in the artificial delimitation of many groups of species.…”

A new Hemigrammus from the upper Río Vaupés, Colombia (Characiformes: Characidae), with a discussion on the presence of an enlarged urogenital papilla in the family

“…Hemigrammus ataktos was compared with species belonging to the Hyphessobrycon heterorhabdus group ( sensu Géry, ) by Marinho et al . (). Lima et al .…”

“…tuyensis García‐Alzate, Román‐Valencia & Taphorn, 2008; and Hy. vilmae Géry, 1966, from which it differs, among other characters, by exhibiting scales on the basis of the caudal fin (see Marinho et al ., ). On the other hand, Hyphessobrycon species that present a colour pattern similar to that in He.…”

A new sexually dichromatic miniature Hyphessobrycon (Teleostei: Characiformes: Characidae) from the Rio Formiga, upper Rio Juruena basin, Mato Grosso, Brazil, with a review of sexual dichromatism in Characiformes

“…(a), (b)]. Secondary sexual dimorphism is frequently reported and discussed among characiforms, mainly regarding the presence of bony hooks on fins (Wiley & Collette, ; Fink & Weitzman, ; Weitzman & Fink, ; Weitzman et al ., ; Malabarba & Weitzman, , , ; Lima & Sousa, ; Camelier & Zanata, ; Vieira et al ., ) or shape of the dorsal and anal fins (Costa & Géry, ; Weitzman & Palmer, ; Moreira et al ., , b ; Teixeira et al ., ; Ingenito et al ., ; Dagosta et al ., ; Marinho et al ., ; Pastana & Ohara, ). Although sexual dichromatism in Characidae has been known for over a century (Eigenmann, , ), descriptions of such dimorphism are still scarce in taxonomic literature.…”