Centromochlus meridionalis, a new catfish species from the southern Amazonian limits, Mato Grosso State, Brazil (Siluriformes: Auchenipteridae)

Abstract

Centromochlus actually comprises eleven species, being the most problematic genus among the Centromochlinae, including morphologically heterogeneous taxa. The Centromochlus species have a wide distributional area on northern South America. Centromochlus meridionalis, new species, is described from headwaters of rio Teles Pires, contributor of rio Tapajós, Mato Grosso State, Brazil, and represents one of the southernmost records of a centromochlin catfish for Meridional Amazon rivers. Centromochlus meridionalis is promptly distinguished from its congeners by the small orbital diameter (relative to head length), and also by the combination of absence of first nuchal plate, anterior margin of dorsal-fin spine smooth, six branched rays in anal fin, seven pairs of ribs and 34 vertebrae. They are small sized catfishes with adults between 33 to 61 mm in standard length. The modified male anal fin is conspicuous, with the third unbranched ray enlarged, about twice the width of first unbranched ray. The new species inhabits a region strongly endangered by environmental changes due to expansion of agropecuary activities on Brazilian Amazon, which include this species in an uncertain situation regarding the conservation status of its natural population.Centromochlus abriga atualmente onze espécies, sendo o gênero mais problemático dentre os Centromochlinae, incluindo táxons morfologicamente heterogêneos. As espécies de Centromochlus apresentam uma ampla área de distribuição no norte da América do Sul. Centromochlus meridionalis, espécie nova, é descrita para as cabeceiras do rio Teles Pires, formador do rio Tapajós, Mato Grosso, Brasil, e representa um dos registros mais ao sul de um bagre centromoclíneo para os riachos da Amazônia meridional. Centromochlus meridionalis é prontamente distinguido de todos os seus congêneres, pelo diâmetro orbital pequeno (em relação ao comprimento da cabeça), e ainda pela combinação da ausência de primeira placa nucal, margem anterior do espinho da nadadeira dorsal lisa, seis raios ramificados na nadadeira anal, sete pares de costelas e 34 vértebras. São bagres de pequeno porte com adultos entre 33 e 61 mm de comprimento padrão. A nadadeira anal de machos sexualmente maduros é conspicuamente modificada, na qual o terceiro raio indiviso é muito largo, cerca do dobro da espessura do primeiro raio ramificado. O registro desta espécie nova ocorre em uma região fortemente ameaçada por alterações ambientais decorrentes da expansão de atividades agropecuárias na Amazônia Brasileira, a qual coloca esta espécie em uma situação incerta quanto ao estado de conservação da sua população natural.

New species of the catfish genus Tatia (Siluriformes:Auchenipteridae) from the rio Teles Pires, upper rio Tapajós basin, Brazil

“…Evidence from the caudal peduncle form, nonetheless, justifies the placement of the new species in Tatia. Furthermore, T. melanoleuca lacks the elongated maxilla, which is diagnostic for Centromochlus (Sarmento-Soares et al, 2013), the centromochlin genus most similar to Tatia.…”

A preliminary inventory of the catfishes of the lower Rio Nhamundá, Brazil (Ostariophysi, Siluriformes)

“…One of these records ( Centromochlus sp., INPA 35087) was also recorded in the literature survey (Sarmento-Soares et al 2013). As stated previously, because this lot was out on loan at the time of writing this manuscript, we were not able to examine the specimens and have therefore omitted this species from the total species count due its ambiguity.…”

“…We were unsure of the identity of the second—a record of a Centromochlus sp. "pigmento" (INPA 35087) referred to by Sarmento-Soares et al (2013) as Centromochlus sp.—and so have not included this species in the checklist.…”

Quantifying shortfalls in the knowledge on Neotropical Auchenipteridae fishes

“…In the case of Auchenipteridae, 60% of the species described in the last decade resulted from field inventories (e.g. Akama & Ferraris, 2011;Sarmento-Soares, Cabeceira, Carvalho, Zuanon, & Akama, 2013;Sarmento-Soares, Lazzarotto, Py-Daniel, & Leitão, 2016). The high number of species recently discovered in the field may be related to the inconspicuousness of Auchenipteridae catfishes.…”