Fish fauna from a fragmented river in the Atlantic Forest / Fauna de peixes de um rio fragmentado na Mata Atlântica

Abstract: This study sought to identify the ichthyofauna composition of the Muzambinho River, an upland tributary of the Paraná River. We also investigate whether waterfalls in the region can serve as barriers to the dispersal of fish species. For this purpose, collections were carried out at 34 points on the Muzambinho River using different techniques. In all, 37 species were recorded, some of which were endemic, and the majority were native. Among these species, some are predominant in degraded places and can be used as bioindicators. The results also demonstrate zonation in the ichthyofauna composition in Muzambinho that segregates the fauna into three sessions separated by waterfalls: Lower Muzambinho, Upper Muzambinho, and Sao Domingos. We conclude that, for the ideal preservation of the ichthyofauna of the Muzambinho River, it is necessary to preserve its sections independently, which would guarantee the maintenance of naturally isolated strains.

Resumo: Este estudo buscou identificar a composição da ictiofauna do rio Muzambinho, um tributário de terras altas do Rio Paraná. Também buscamos investigar se as cachoeiras da região podem servir de barreiras para dispersão de espécies de peixes. Para isso, foram realizadas coletas em 34 pontos do Rio Muzambinho, com diferentes técnicas. Ao todo foram registradas 37 espécies de peixes, sendo algumas endêmicas e a maioria nativa. Dentre essas espécies algumas são predominantes em locais degradados e podem ser usadas como bioindicadores. Os resultados também demonstram que há uma zonação na composição ictiofaunística no Muzambinho que segrega a fauna em três sessões separadas por cachoeiras, Baixo Muzambinho, Alto Muzambinho e São Domingos. Concluímos que para a ideal preservação da ictiofauna do rio Muzambinho é necessária a preservação independente de suas sessões o que garantiria a manutenção de linhagens naturalmente isoladas.

New species of the Pseudancistrus barbatus group (Siluriformes, Loricariidae) with comments on its biogeography and dispersal routes.

A new species of Pseudancistrus is described from the Tapajós Basin, and assigned to the P. barbatus group by having hypertrophied odontodes along the snout and lacking evertible cheek plates. The new species is distinguished from other species in that group (P. barbatus, P. corantijniensis, P. depressus and P. nigrescens) by its pattern of spots, length and color of snout odontodes, greater head depth, cleithral width, anal-fin spine length, peduncle depth and internares width. Molecular phylogenetic results corroborate placement of the new species in the Pseudancistrus barbatus group which is otherwise distributed in the Xingu Basin and rivers draining the Guyana Shield into the Atlantic Ocean. Topology tests strongly reject alternative hypotheses supporting close relationships with Guyanancistrus, Lithoxancistrus or the species Pseudancistrus pectegenitor, P. sidereus and P. genisetiger. Additionally, we propose two hypotheses on the distribution of the new species in the rio Tapajós, a Brazilian Shield drainage. The first one proposes that ancestral stock of the P. barbatus group was widely distributed throughout rivers draining the Guyana and Brazilian shields, and the species P. zawadzkii and Pseudancistrus sp. L17 are in the limit of the distribution for the group in Tapajós and Xingu rivers. The second hypothesis proposes that ancestral stock of the P. barbatus group was restricted to Guyana Shield rivers, and that headwater capture events permitted several dispersal routs through Guyana and Amazon rivers, permitted that the ancestral lineages of Pseudancistrus sp. L17 and P. zawadzkii reached the rivers of Amazon basin.

Pareiorhina hyptiorhachis, a new catfish species from Rio Paraíba do Sul basin, southeastern Brazil (Siluriformes, Loricariidae).

Pareiorhina hyptiorhachis is described from Ribeirão Fernandes and Rio Pomba, Rio Paraíba do Sul basin, Brazil. The new species is distinguished from its congeners (Pareiorhina brachyrhyncha, Pareiorhina carrancas, Pareiorhina cepta, and Pareiorhina rudolphi) by the presence of a conspicuous ridge on the trunk posterior to the dorsal fin (postdorsal ridge), simple teeth, a completely naked abdomen, a round dorsal profile of the head, greater suborbital depth and greater head width. We discuss the distributional pattern of the new species and its congeners and hypothesize that headwater capture is responsible for the distribution of Pareiorhina species across different watersheds in southeastern of Brazil.

ResumoPareiorhina hyptiorhachis é descrita do ribeirão Fernandes e do rio Pomba, bacia do rio Paraíba do Sul, Brasil. A nova espécie é distinguida de suas congêneres (Pareiorhina brachyrhyncha, Pareiorhina carrancas, Pareiorhina cepta, e Pareiorhina rudolphi) por caracteres relacionados a presença de uma quilha conspícua na superficie pós-dorsal do tronco, dentes simples, abdomen completamente nú, perfil dorsal da cabeça arredondado, altura do sub-orbital e largura da cabeça. Nós discutido o padrão de distribuição da nova espécie e de seus congêneres e a hipótese de que a captura de cabeceira é responsável pela distribuição das espécies de Pareiorhina através das diferentes bacias hidrográficas do sudeste do Brasil.