Seven new species of the killifish genus Rivulus (Cyprinodontiformes: Rivulidae) from the Paraná, Paraguay and upperAraguaia river basins, central Brazil

Abstract

Seven new species of the Rivulus punctatus group collected during recent field studies in central Brazil are described. Rivulus dapazi n. sp., from the upper rio Correntes drainage, rio Paraguay basin, is diagnosed by a unique color pattern of the anal and caudal fins in males; R. cyanopterus n. sp., from the upper rio São Lourenço drainage, rio Paraguay basin, is diagnosed by a unique color pattern of the anal fin in both sexes; R. rossoi n. sp., from the rio Inhanduí drainage, rio Paraná basin, is diagnosed by a unique color pattern of the caudal fin in males and a reduced number of gill rakers on the first branchial arch; R. litteratus n. sp., from the upper rio Araguaia basin, is diagnosed by unique color patterns of flank in males and caudal fin in females; R. rutilicaudus n. sp., from the rio Verde drainage in Goiás, rio Paraná basin, is diagnosed by a unique color pattern of the caudal fin in females; R. scalaris n. sp., from the rio Sucuruí, rio Aporé, rio Correntes and rio Taquari drainages, rio Paraná basin, is diagnosed by a unique color pattern of the flank in males; and, R. egens n. sp., from the upper rio Verde drainage in Mato Grosso do Sul, rio Paraná basin, is distinguished by a combination of frontal E-scale pattern and the absence of red marks on the caudal fin in males. Combinations of other color patterns and morphological features, including number of scales of the longitudinal series, number of dorsal, anal, caudal and pectoral fin-rays, relative position of dorsal-fin origin and anal-fin rays, and number of vertebrae, are also useful in identification of the new species, but phylogenetic relationships among them are unknown at the present. A key to identification of species of Rivulus from the rio Paraná-Paraguay basin and adjacent headstreams is provided.<br>Sete espécies novas do grupo Rivulus punctatus coletadas durante estudos de campo recentes no Brasil central são descritas. Rivulus dapazi sp. n., da drenagem do alto rio Correntes, bacia do rio Paraguai, é diagnosticada por um padrão de colorido exclusivo das nadadeiras anal e caudal em machos; R. cyanopterus sp. n., da drenagem do alto rio São Lourenço, bacia do rio Paraguai, é diagnosticada por um padrão de colorido exclusivo da nadadeira anal em ambos sexos; R. rossoi sp. n., da drenagem do rio Inhanduí, bacia do rio Paraná, é diagnosticada por um padrão de colorido exclusivo da nadadeira caudal em machos e número reduzido de rastros branquiais no primeiro arco branquial; R. litteratus sp. n., da drenagem do alto rio Araguaia, é diagnosticada por um padrão de colorido exclusivo do flanco em machos e da nadadeira caudal em fêmeas; R. rutilicaudus sp. n., da drenagem do rio Verde em Goiás, bacia do rio Paraná, é diagnosticada por um padrão exclusivo da nadadeira caudal em fêmeas; R. scalaris sp. n., das drenagens do rios Sucuruí, Aporé, Correntes e Taquari, bacia do rio Paraná, é diagnosticada por um padrão de colorido exclusivo do flanco em machos; e, R. egens sp. n., da drenagem do alto rio Verde no Mato Grosso do Sul, bacia do ri...

Three new species of the killifish genus Melanorivulus from the Rio Paraná Basin, central Brazilian Cerrado (Cyprinodontiformes, Aplocheilidae)

“…About 50 valid species are presently placed in Melanorivulus, formerly considered as a subgenus of Rivulus Poey, 1860 (Costa 2011). Melanorivulus is similar to other South American aplocheiloid killifishes living in similar biotopes, such as Anablepsoides Huber, 1992, Atlantirivulus Costa, 2008,2005; the M. pinima group, easily diagnosed by the reduction of black pigmentation on the head and humeral region in males, presence of longitudinal rows of red dots on the flank, and a longitudinally elongated white to light yellow mark above caudal spot in females (Costa 2007a), and the M. pictus group, diagnosed by a deeper body (i.e., body depth reaching about 25 % SL) and oblique red bars on the flank (Costa 2017). Eleven of the 14 endemic species are members of the last group, which are mostly concentrated in the rivers draining the Caiapó range and in the south adjacent areas of the middle Rio Paraná Basin (Costa 2005(Costa , 2012.…”

“…Previous studies indicate that the Sucuruí, Aporé, Corrente, Verde and Claro river drainages, which drain the south-eastern slope of the Caiapó range and flow directly to the Rio Paranaíba as part of the upper Rio Paraná Basin, concentrates a great diversity of species of Melanorivulus (Costa 2005(Costa , 2007a(Costa , b, 2008. These species are often members of clades endemic to Caiapó range drainages, including those belonging to the upper Rio Araguaia Basin, on its northern slope (e.g., Costa 2006).…”

“…4), suggesting that it may be more closely related to M. egens (Costa 2005: fig. 11) and M. linearis (Fig.…”

“…In September 1994, efforts were directed to firstly sample typical Melanorivulus habitats along the Paraná River Basin, but based on the great morphological variability found among populations inhabiting close neighbouring areas, Costa (1995) concluded that all populations of this vast geographical area belong to a single polymorphic species, M. pictus. However, after more accurate field studies since 2004, numerous new species have been continuously described for the Paraná and other adjacent river basins (e.g., Costa 2005Costa , 2006Costa , 2012Costa , 2017Deprá et al 2017). These studies have indicated that each species is limited to small areas and that different species may inhabit the same river drainage at different altitudes (Costa 2007b(Costa , 2017Volcan et al 2017).…”

Unrecognized biodiversity in a world’s hotspot: three new species of Melanorivulus (Cyprinodontiformes: Rivulidae) from tributaries of the right bank of the Rio Paraná basin, Brazilian Cerrado

“…The Melanorivulus pictus species group currently comprises 18 species (Volcan et al 2017, Costa 2018, with 16 species occurring in the Rio Paraná basin: M. apiamici (Costa, 1989) in the Rio Paraná, M. egens (Costa, 2005), in the Rio São Domingos, M. formosensis (Costa, 2008) and M. nigromarginatus Costa, 2018 for the Rio Corrente, M. giarettai (Costa, 2008) for the Rio Araguari basin, M. leali Costa, 2013 for the Rio Grande basin, M. nigropunctatus Volcan, Klotzel & Lanés, 2017 and M. ofaie Volcan, Klotzel & Lanés, 2017 for the Rio Verde basin, M. faucireticulatus (Costa, 2008), M. pictus (Costa, 1989) and M. vittatus (Costa, 1989) for the Rio Claro basin, M. polychromus Nielsen, 2016 for the Rio São José dos Dourados basin, M. rutilicaudus (Costa, 2005) for the Rio Verde basin, M. scalaris (Costa, 2005) for the Rio Sucuruí basin, M. proximus Costa, 2018 for Rio Aporé and M. linearis Costa, 2018 for the upper Rio Pardo basin. Two other species occur exclusively in the upper Rio Tocantins and Araguaia basin: M. planaltinus (Costa & Brasil, 2008) for the Rio Cocal and M. litteratus (Costa, 2005) for the Salto stream, respectively.…”