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A new species of Knodus from the Rio Cupari, a right-bank tributary of the lower Rio Tapajós, is described. Among its congeners, the new species shares exclusively with K. figueiredoi the presence of only uni-tricuspid teeth in the premaxilla, maxilla and dentary. Knodus borari differs from K. figueiredoi by the colour pattern and morphological characteristics. The new species is the fifth species of the genus described from the Rio Tapajós basin, and the second restricted to the lower portion of the basin. This is additional evidence that the lower Rio Tapajós basin is a region of ichthyofaunal endemism.

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A new species of Tatia is described from rio Tapajós, upstream of the rapids of São Luiz do Tapajós, Pará State, Brazil. The new species is identified and diagnosed from its congeners through morphological characteristics such as the absence of an adipose fin, which is shared with T. akroa and T. britskii; the composition of the cranial roof elements; the color pattern consisting of dorsolateral dark dots formed by both dermal and epidermal pigments; as well as several morphometric measures. The new species is a Centromochlinae fish that feeds on insects on the surface of the water at night and it is probably endemic to rio Tapajós basin.(AU)

Uma nova espécie de Tatia é descrita do rio Tapajós, à montante das corredeiras de São Luiz do Tapajós, Estado do Pará, Brasil. A nova espécie é identificada e diagnosticada das congêneres por características morfológicas, tal como a ausência de nadadeira adiposa, compartilhada com T. akroa e T. britskii; a composição dos elementos do teto craniano; o padrão de colorido, consistindo em pequenas pintas escuras dorsolaterais formadas por pigmentos dérmicos e epidérmicos; assim como por várias características morfométricas. A espécie nova é um peixe Centromochlinae que se alimenta de insetos na superfície da água durante a noite e provavelmente é endêmica da bacia do rio Tapajós.(AU)

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ABSTRACT A redescription of Bryconops gracilis is provided, a species poorly known for more than a century. Bryconops gracilis differs from all congeners by having the following combination of features: eight branched pelvic-fin rays, 31-36 anal-fin rays, 15-17 predorsal scales arranged in a regular series, two rows of premaxillary teeth, and 53-60 lateral-line scales. The species was often misidentified as B. alburnoides by sharing an overall elongated body shape, caudal fin yellowish in life, and a high number of lateral-line scales. A diagnosis between B. alburnoides and B. gracilis is provided. The holotype of B. gracilis which for many years had whereabouts unknown, was recovered, examined and illustrated by CT-Scan. Additionally, more detailed information about the type locality, morphology, color pattern (including in living specimens), habitat and distribution pattern of species are provided.

RESUMO A redescrição de Bryconops gracilis, uma espécie pouco conhecida por mais de um século, é fornecida. Bryconops gracilis difere de todas as congêneres por apresentar a seguinte combinação de caracteres: oito raios ramificados na nadadeira pélvica, 31-36 raios ramificados na nadadeira anal, 15-17 escamas pré-dorsais dispostas em uma série regular, duas séries de dentes no pré-maxilar e 53-60 escamas na linha lateral. A espécie foi frequentemente identificada erroneamente como B. alburnoides por compartilhar a forma geral do corpo alongada, nadadeira caudal amarelada em vida e um grande número de escamas na linha lateral. Uma diagnose entre B. alburnoides e B. gracilis é fornecida. O holótipo de B. gracilis que por muitos anos teve paradeiro desconhecido, foi recuperado, examinado e ilustrado através de CT-Scan. Adicionalmente, informações mais detalhadas sobre a localidade tipo, morfologia, padrão de coloração (incluindo em espécimes vivos), habitat e padrão de distribuição da espécie são fornecidas.

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ABSTRACT A new species of Bryconops is described based on its unique caudal-fin color pattern, with a dark blotch occupying the mid-basal region of the caudal-fin dorsal lobe, and a combination of 29-32 branched anal-fin rays, 44-47 perforated scales in the lateral line, six rows of scales above the lateral line, and a deep body (30.3-31.7 % SL). The new species belongs to the subgenus Bryconops based on its edentulous and short maxilla, with the posterior extension of that bone not reaching the junction between the second and third infraorbitals. The new species was previously reported in the literature as B. caudomaculatus. However, these species differ from each other in morphometric and meristic characters, as well as in color pattern. Comments on distribution of Bryconops species in coastal drainages of Suriname and French Guiana additional support for biogeographic hypotheses in this area.

RESUMO Uma nova espécie de Bryconops é descrita com base no colorido único da nadadeira caudal, com uma mancha escura ocupando a região médio-basal do lobo superior da nadadeira caudal, e uma combinação de 29-32 raios ramificados na nadadeira anal, 44-47 escamas perfuradas na linha lateral, seis séries de escamas acima da linha lateral e corpo alto (30,3-31,7 % CP). A nova espécie pertence ao subgênero Bryconops com base na maxila edêntula e curta, com extensão posterior deste osso não atingindo a junção entre segundo e terceiro infraorbitais. A nova espécie foi reportada anteriormente na literatura como B. caudomaculatus. Contudo, essas espécies diferem uma da outra em caracteres merísticos e morfométricos, bem como no padrão de coloração. Comentários sobre a distribuição das espécies de Bryconops em drenagens costeiras do Suriname e Guiana Francesa fornecem suporte adicional para as hipóteses biogeográficas nesta área.

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Amazonian waters are classified into three biogeochemical categories by dissolved nutrient content, sediment type, transparency, and acidity-all important predictors of autochthonous and allochthonous primary production (PP): (1) nutrient-poor, low-sediment, high-transparency, humic-stained, acidic blackwaters; (2) nutrient-poor, low-sediment, high-transparency, neutral clearwaters; (3) nutrient-rich, low-transparency, alluvial sediment-laden, neutral whitewaters. The classification, first proposed by Alfred Russel Wallace in 1853, is well supported but its effects on fish are poorly understood. To investigate how Amazonian fish community composition and species richness are influenced by water type, we conducted quantitative year-round sampling of floodplain lake and river-margin habitats at a locality where all three water types co-occur. We sampled 22,398 fish from 310 species. Community composition was influenced more by water type than habitat. Whitewater communities were distinct from those of blackwaters and clearwaters, with community structure correlated strongly to conductivity and turbidity. Mean per-sampling event species richness and biomass were significantly higher in nutrient-rich whitewater floodplain lakes than in oligotrophic blackwater and clearwater river-floodplain systems and light-limited whitewater rivers. Our study provides novel insights into the influences of biogeochemical water type and ecosystem productivity on Earth's most diverse aquatic vertebrate fauna and highlights the importance of including multiple water types in conservation planning.

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Bryconops cyrtogaster, a poorly known species endemic from the Oyapock River at the border between French Guyana and Brazil, is redescribed herein based on examination of available type material, as well as newly collected material. Additionally, a new rheophilic species from the rio Jari rapids, lower Amazon basin, Brazil, is described. The two species belong to the subgenus Creatochanes and are unique among the congeneres for possessing a posteriorly positioned humeral blotch at the level of the sixth and seventh lateral line scales. They differ from each other by meristic and morphometric characters. The list of endemic species in the rio Jari basin is revised.

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A new species of Knodus is described from the rio Cupari drainage, a tributary from the right margin of the lower rio Tapajós, Pará State, Brazil. The new species differs from its congeners, except K. geryi, by having a dark basal blotch on each caudal fin lobe (vs. caudal fin lobes with sparse chromatophores, lacking basal blotches) and, with the exception of K. borki, K. heteresthes, and K. pasco, by having 10-12 scales around the caudal peduncle (vs. 13-15).

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A new species of Bryconops is described from the rio Maicuru, a tributary of the left margin of the lower Amazon River, Pará, Brazil. Bryconops chernoffi new species, differs from all its congeners by the presence of an elongated dark patch of pigmentation immediately after the posterodorsal margin of the opercle, running vertically from the supracleithrum to the distal margin of the cleithrum (vs. absence of a similar blotch), and by a dark dorsal fin with a narrow hyaline band at middle portion of dorsal-fin rays (vs. dorsal fin hyaline or with few scattered chromatophores). It differs further from all its congeners, except B. colanegra, by the presence of a blurred black stripe at the anal fin base. It differs from B. colanegra by possessing fewer predorsal scales (8-9 vs. 10-11) and in that the third infraorbital contacts the preopercle ventrally (vs. third infraorbital not contacting preopercle ventrally). The new species is assigned to the subgenus Creatochanes by the number of maxillary teeth, and ossification and denticulation of the gill rakers.

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The fish fauna of freshwater streams in the Tapajos National Forest was surveyed and a list of species is presented. The sampling was conducted from 2012 to 2013 during the dry season. Fish were collected with dip nets and seine nets in 22 streams of 1(st) to 3(rd) order. Sampling resulted in 3035 specimens belonging to 117 species, 27 families and six orders. The most abundant species were Bryconops aff. melanurus, Hemigrammus belottii, and Hemigrammus analis. Four undescribed species were recognized, one of which is known only from the area of this study. A significant dissimilarity was observed in fish species composition among drainage systems. This is the first survey of the stream ichthyofauna in the Tapajós National Forest, and it presents relevant information for future studies and decision-making in the management and conservation of fish fauna in this conservation unit.

ResumoA ictiofauna de riachos na Floresta Nacional do Tapajós foi inventariada e uma lista de espécies é apresentada. As amostragens foram realizadas de 2012 a 2013 durante o período de águas baixas. Os peixes foram coletados com redes de arrasto e peneiras em 22 riachos de 1ª a 3ª ordem. As amostragens resultaram em 3035 espécimes pertencentes a 117 espécies, 27 famílias e seis ordens. As espécies mais abundantes foram Bryconops aff. melanurus, Hemigrammus belottii and Hemigrammus analis. Quatro espécies novas foram reconhecidas, sendo uma conhecida apenas da área de estudo até o presente momento. Foi observada uma dissimilaridade significativa na composição de espécies de peixes entre os sistemas de drenagem. Esse é o primeiro inventário da ictiofauna de riachos na Floresta Nacional do Tapajós e apresenta informações relevantes para subsidiar estudos futuros e a tomada de decisões no gerenciamento da ictiofauna nessa Unidade de Conservação.

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A new species of Bryconops is described from a right tributary of the lower Tapajós River, State of Pará, Brazil. Bryconops munduruku, sp. nov., differs from its congeners, except B. inpai and B. piracolina, by having a black adipose fin (vs. adipose fin hyaline in alcohol) and, except B. inpai, by possessing two humeral blotches (vs. lack of humeral blotch or only one humeral blotch). Bryconops munduruku differs from B. inpai by having a uniform color pattern on the posterior portion of the side of the body (vs. a dark stripe extending posteriorly from the half of the anal-fin base onto the base of the middle caudal-fin rays). It differs further from B. inpai and B. piracolina by the presence of a black adipose fin that is hyaline along its base (vs. entirely black adipose fin in B. inpai and B. piracolina). The new species is allocated in the subgenus Creatochanes by having a maxillary bone with one to three teeth on both sides, and its posterior extension reaching the junction of second and third infraorbital bones.

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