Revision of the smaller-sized dorados (Salminus), with comments on the monophyly of the genus and its biogeography (Characiformes: Bryconidae).

A revision of the genus Salminus, excluding the large-sized species S. brasiliensis and S. franciscanus, is presented. In addition to the two large-sized species, four additional Salminus species are recognized: Salminus affinis Steindachner, from the río Magdalena, río Sinú, and río Rancheria basins, Colombia; Salminus hilarii Valenciennes, from the rio Paraná, rio São Francisco, and rio Jaguaribe basins, Brazil, Argentina, and Paraguay; Salminus iquitensis (Nakashima), new combination, from the western portion of the Amazon basin, rio Branco, and río Orinoco basins, Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela; and Salminus santosi new species, from the rio Tocantins basin, Brazil. These four species are described/redescribed and illustrated, and a key to the species belonging to the genus is presented. Comments on the diagnosis of the genus Salminus and its biogeography taking into account recent phylogenetic hypotheses published for the genus, are presented.

Fishes of the Mitú Region: middle basin of the río Vaupés, Colombian Amazon / Peces de la región de Mitú: cuenca media del río Vaupés, Amazonia colombiana

Abstract: The Amazon River basin hosts the most diverse freshwater ichthyofauna in the world, and yet huge areas of the basin remain unexplored. This is the case for the upper tributaries of the rio Negro, especially those draining the Colombian territory. Here we present a list of 224 species derived from the examination of specimens collected in the Mitú region (Vaupés Department, Colombia), the middle basin of the río Vaupés. Of the species identified in our study, 10 species are recorded from Colombia for the first time, and 26 species are newly recorded from the Colombian Amazon. The number of species we present here comprise almost one-third of the known species diversity of the Colombian Amazon and nearly a tenth of the total number of those known across the entirety of the Amazon basin. The most diverse orders were Characiformes (120 species) and Siluriformes (65 species), and the remaining six orders comprised less than 20% of total species. The study area comprised blackwater systems, which are considered to be nutrient-poor environments. We discuss some ecological aspects that might explain how this highly diverse ichthyofauna originates and is maintain in less productive systems. The list presented here adds an important number of new records and complements the information derived from previous studies, carried out thus far with regards to the fish fauna of the Colombian Amazon.

Resumo: La cuenca del río Amazonas alberga la ictiofauna dulceacuícola más diversa del mundo, sin embargo, grandes áreas de la cuenca permanecen inexploradas. Este es el caso de los afluentes de la parte alta del río Negro, especialmente los sistemas que drenan el territorio colombiano. A continuación, presentamos un listado de 224 especies derivadas del análisis de especímenes recolectados en la región de Mitú, cuenca media del río Vaupés (Departamento de Vaupés, Colombia). De las especies identificadas, 10 especies se registran en Colombia por primera vez y 26 especies para la Amazonía colombiana. El número de especies que presentamos aquí comprende casi un tercio de las especies conocidas para la Amazonía colombiana y casi una décima parte del total de las conocidas para la gran cuenca del Amazonas. Los órdenes más diversos fueron Characiformes (120 especies) y Siluriformes (65 especies), y los seis órdenes restantes comprendieron menos del 20% del total de especies. El área de estudio comprende sistemas de aguas negras que se consideran ambientes poco productivos por sus bajos contenidos de nutrientes. Discutimos aquí algunos aspectos ecológicos que podrían explicar cómo esta ictiofauna tan diversa tiene su origen y es mantenida en estos sistemas poco productivos. La información derivada del presente estudio adiciona nuevos registros de especies de peces para Colombia, y complementa la información derivada de los estudios realizados a la fecha en la Amazonía colombiana.

Fishes from the Colombian Amazonia region: species composition from the river systems within the rainforest biome / Peces de la región de la Amazonía Colombiana: composición de especies de los sistemas fluviales del bioma de selva húmeda

Abstract The Colombian Amazon region is part of the Neotropical rainforest (humid forest biome) covering an area of 483,163 km2 and includes tributaries of both the Amazon and Orinoco River basins. The aquatic ecosystems found there include: rivers and alluvial plains originating in Andean headwaters, on eroded soils of tropical forests in the lowlands, and Guiana Shield formations, comprising a dense fluvial drainage network in the lowlands, with Paleogene/Neogene geological formations (terra firme streams in higher places that don't usually flood) and Paleozoic (shield streams); and Andean and Guiana Shield streams above 200-250 m a.s.l. We present here an exhaustive compilation of published information, supported by fish collections, consisting of a list of 1104 species distributed in 375 genera, 53 families, and 16 orders. We include occurrence data of these species in each sub-basin. The presence/absence species matrix was analyzed using a dendrogram and non-metric multidimensional scaling (NMDS) analysis to identify patterns of similarity between basins and sub-basins. We evaluated species composition between basins and among the different geological origins using PERMANOVA. The dendrogram shows co-occurrences of 404 species in the two basins. It also shows two clear groupings of the sub-basins of the Amazon (except Guainía-Negro drainages) and those of the Orinoco. Within the Amazon Basin, there are two nodes according to the geological origin: systems of Andean origin and those of the lowlands. The dendrogram results are consistent with the NMDS analysis, which shows a clear grouping according to the connectivity of the basins; the Guainía-Negro is included in the Amazon basin. Species distribution patterns were supported by the PERMANOVA, and differed significantly between basins (F = 4.3, R = 0.26, P = 0.003) and geological origin (F = 3.6, R = 0.23, P = 0.003). The number of species in this study represents almost a fifth of the ichthyofauna of the Neotropics and about a third of that of the Amazon River basin; clearly supporting Colombia's status among the countries with the greatest diversity of freshwater fish species of the planet. We include here a significant number of new records (75 spp), provide a first approximation of the distribution patterns, and a framework for future biogeographical studies.

Resumo La región de la Amazonía colombiana hace parte del bosque húmero neotropical (bioma de selva húmeda) abarcando un área de 483.163 km2 e incluye afluentes de las cuencas del Amazonas y Orinoco. Los ecosistemas acuáticos encontrados allí incluyen: ríos y llanuras aluviales, originándose en cabeceras andinas, en suelos erosionados de bosques tropicales en tierras bajas y en formaciones de escudos; conformando una densa red fluvial en tierras bajas con formaciones geológicas paleógenas-neógenas (arroyos de terra firme en sitios elevados que usualmente no se inundan) y paleozoicas (arroyos de escudo); y arroyos andinos y del escudo Guayanés por encima de 200-250 m s.n.m. Presentamos aquí una recopilación exhaustiva de información publicada, sustentada por colecciones ictiológicas, consistiendo en una lista de 1104 especies distribuidas en 375 géneros, 53 familias y 16 órdenes. Incluimos datos de estas especies en cada subcuenca. La matriz de presencia/ausencia de especies fue analizada usando un dendrograma y un análisis de escalamiento multidimensional no métrico (NMDS) para identificar patrones de similitud entre cuencas y subcuencas. Se evaluó la composición de especies entre cuencas y entre los diferentes orígenes geológicos usando PERMANOVA. El dendrograma refleja coocurrencia de 404 especies en las dos cuencas. También muestra dos agrupaciones claras de las subcuencas del Amazonas (excepto Guainía-Negro) y las del Orinoco. Dentro de la cuenca amazónica existen dos nodos según el origen geológico: los sistemas de origen andino y los de tierras bajas. Los resultados del dendrograma son consistentes con el análisis NMDS, el cual muestra una clara agrupación según la conectividad de las cuencas; el Guainía-Negro está incluido en la cuenca del Amazonas. Los patrones de distribución de especies fueron respaldados por el PERMANOVA y difirieron significativamente entre cuencas (F = 4.3, R = 0.26, P = 0.003) y origen geológico (F = 3.6, R = 0.23, P = 0.003). El número de especies en este estudio representa casi la quinta parte de la ictiofauna del Neotrópico y alrededor de un tercio de la de la cuenca del río Amazonas; soportando el estatus de Colombia entre los países con mayor diversidad de especies de peces de agua dulce del planeta. Incluimos aquí un número importante de nuevos registros (75 spp), brindamos una aproximación de los patrones de distribución y un marco para futuros estudios biogeográficos.

Rediscovering species: redescription of Bryconops gracilis (Characiformes: Iguanodectidae), an often-misidentified species

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.

A new Hyphessobrycon (Characiformes: Characidae) of the Hyphessobrycon heterorhabdus species-group from the lower Amazon basin, Brazil

A new species of Hyphessobrycon belonging to the Hyphessobrycon heterorhabdus species-group from the lower rio Tapajós, state of Pará, Brazil, is described. The new species is allocated into the Hyphessobrycon heterorhabdus species-group due to its color pattern, composed by an anteriorly well-defined, horizontally elongated humeral blotch that becomes diffuse and blurred posteriorly, where it overlaps with a conspicuous midlateral dark stripe that becomes blurred towards the caudal peduncle and the presence, in living specimens, of a tricolored longitudinal pattern composed by a dorsal red or reddish longitudinal stripe, a middle iridescent, golden or silvery longitudinal stripe, and a more ventrally-lying longitudinal dark pattern composed by the humeral blotch and dark midlateral stripe. It can be distinguished from all other species of the group by possessing humeral blotch with a straight or slightly rounded ventral profile, lacking a ventral expansion present in all other species of the group. The new species is also distinguished from Hyphessobrycon heterorhabdus by a 9.6% genetic distance in the cytochrome c oxidase I gene. The little morphological distinction of the new species when compared with its most similar congener, H. heterorhabdus, indicates that the new species is one of the first truly cryptic fish species described from the Amazon basin.(AU)

Uma nova espécie de Hyphessobrycon pertencente ao grupo Hyphessobrycon heterorhabdus é descrita da região do baixo rio Tapajós, estado do Pará, Brasil. A nova espécie é incluída no grupo Hyphessobrycon heterorhabdus devido ao seu padrão de coloração, composto por uma mancha umeral alongada, anteriormente bem definida, que se torna difusa e borrada posteriormente, onde se sobrepõe a uma conspícua faixa escura médio-lateral que se torna borrada próxima ao pedúnculo caudal, e pela presença, em exemplares vivos, de um padrão longitudinal tricolor, composto por uma faixa longitudinal vermelha ou avermelhada dorsal, uma faixa média iridescente dourada ou prateada e, mais ventralmente, o padrão longitudinal escuro composto pela faixa escura médio-lateral e mancha umeral. A espécie pode ser distinguida das outras espécies pertencentes ao grupo por possuir uma mancha umeral com região ventral retilínea ou levemente arredondada, sem uma expansão ventral presente nas demais espécies do grupo. A espécie também se diferencia de Hyphessobrycon heterorhabdus por uma distância genética de 9,6% no gene citocromo c oxidase I. A sutil diferença morfológica da nova espécie quando comparada ao seu congênere mais similar, H. heterorhabdus, indica que a nova espécie é uma das primeiras espécies de peixes verdadeiramente crípticas descritas da Bacia Amazônica.(AU)

A new species of Characidium Reinhardt (Characiformes: Crenuchidae) with a unique mid-water behavior from the upper rio Madeira basin, Brazil.

A new species of Characidium is described from headwater tributaries of the upper rio Guaporé, Rio Madeira basin, Mato Grosso state, Brazil. The new species can be diagnosed from all congeners, except Characidium summus, for lacking the preorbital and postorbital stripes. It can be diagnosed from the latter species by having 12 circumpeduncular scales (vs. 14), by an adipose fin present (vs. adipose fin absent), and 10-12 bars along the body (vs. absence of bars), among other characters. The new species is so far only known from direct tributaries of the Rio Guaporé at the Serra da Borda, an isolated plateau 300-800 meters above sea level, and possess a behavior very uncommon within the genus, being a mid-water pelagic fish, instead of the benthic behavior of most congeners. Comments on the putative phylogenetic relationships of the new species, as well as some remarks on its unusual behavior within the genus, are presented.

A new Hyphessobrycon (Characiformes: Characidae) of the Hyphessobrycon heterorhabdus species-group from the Central Amazon basin, Brazil.

A new species of Hyphessobrycon Durbin from the Paraná do Urariá system in Central Amazon region, Amazonas state, Brazil, is described. The new species is allocated into the Hyphessobrycon heterorhabdus species-group due to its color pattern, composed by a well-defined, horizontally elongated humeral blotch continuous with a conspicuous midlateral dark stripe that becomes blurred towards the caudal peduncle, and can be distinguished from all other species of the group by possessing humeral blotch and continuous midlateral stripe broad, occupying vertical height equivalent of two scale rows. A tricolored pattern composed dorsally by a red or reddish longitudinal stripe, a middle iridescent, golden or silvery longitudinal stripe, and ventrally by a variably-developed longitudinal dark stripe is identified as a putative additional character shared by the species of the Hyphessobrycon heterorhabdus species-group. The presence of bony hooks in all fins in mature males of some species of the Hyphessobrycon heterorhabdus species-group is also discussed.

Biogeochemical water type influences community composition, species richness, and biomass in megadiverse Amazonian fish assemblages.

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.

The true identity of Bryconops cyrtogaster (Norman), and description of a new species of Bryconops Kner (Characiformes: Iguanodectidae) from the Rio Jari, lower Amazon basin.

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.

A new Corydoras (Ostariophysi: Siluriformes: Callichthyidae) with an unusual sexual dimorphism from the rio Juruena basin, Brazil.

A new Corydoras is described from the rio Juruena system, upper rio Tapajós drainage, Amazon basin, Brazil. The new Corydoras is distinguished from all congeners by presenting a combination of a conspicuous broad vertical dark bar on head, at the level of the eye (mask), an overall light background color without large blotches or stripes on body or fins, the presence of two to four small dark blotches along the midline, and pectoral spine with antrorse serrations on its posterior margin. Males of the new species possess numerous, well-developed odontodes over the lateral portions of head, pectoral girdle, and pectoral spines, an uncommon feature for the genus. The new species is hypothesized to belong, within the genus Corydoras, either to Lineage 6 or Lineage 9.

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 xaveriellus sp. nov. is described from the upper Río Vaupés basin (Amazon basin), Departamento Guaviare, Colombia. It is distinguished from all congeners by the combination of the following characters: presence of a conspicuous, dark, longitudinal midlateral stripe extending along the body; presence of a conspicuous rounded, horizontally elongated humeral blotch anterior to the beginning of the dark midlateral stripe; seven scale rows between the dorsal fin and lateral line (vs. five to six); and five scale rows between the lateral line and pelvic-fin insertion (vs. three to four). The single mature male of He. xaveriellus possessed a well-developed urogenital papilla, an unusual feature among characids. The presence of an enlarged urogenital papilla in the family is discussed, and comments regarding the putative relationships of the new species are presented.

Redescription of Moenkhausia melogramma (Characiformes: Characidae), a poorly known tetra from the western Amazon basin

Moenkhausia melogramma is herein redescribed, based on the examination of the holotype plus additional specimens from the western Amazon basin in Brazil, Colombia, Peru, and Ecuador. Moenkhausia melogramma shares with M. collettii, M. conspicua, M. copei, M. venerei, and M. flava a broad dark longitudinal stripe across the eye, and a well-defined dark stripe on the anal-fin base. It can be promptly distinguished from these species by having two humeral blotches. Additionally, we provide comments on the putative relationships of Moenkhausia melogramma with the aforementioned congeners and the Hemigrammus lunatus species-group.(AU)

RESUMO Moenkhausia melogramma é redescrita com base no exame do holótipo e exemplares adicionais da bacia amazônica ocidental no Brasil, Colômbia, Peru e Equador. Moenkhausia melogramma compartilha com M. collettii, M. conspicua, M. copei, M. venerei e M. flava a presença de uma faixa larga longitudinal escura que atravessa os olhos e uma linha escura bem definida na base da nadadeira anal. Ela pode ser prontamente distinguida dessas espécies por ter duas manchas umerais. Adicionalmente, fornecemos comentários sobre as possíveis relações filogenéticas de Moenkhausia melogramma com as congêneres supramencionadas e com o grupo de espécies Hemigrammus lunatus.

Description of a new Hemigrammus Gill (Characiformes: Characidae) from the río Madeira basin in Peru and Bolivia.

We described herein a new Hemigrammus from the río Madre de Dios and rio Mamoré basins in southeastern Peru and Bolivia. The new species possess a color pattern similar to those belonging to the Hemigrammus lunatus species-group, i.e., a broad longitudinal dark stripe across the eye and a conspicuous, narrow dark stripe along the anal-fin basis. It can be easily diagnosed from the species belonging to this group by presenting the combination of the following characters: an oval, horizontally elongated humeral blotch, 6-7 upper branch and 10-12 lower branch gill-rakers, up to five cusps on broader maxillary teeth, and by lacking a midlateral dark stripe. Comments on its putative relationships are provided. Additionally, we updated the geographical distribution of Hemigrammus lunatus and H. machadoi based on an exhaustive survey of material deposited in collections. [Species Zoobank registration: urn:lsid:zoobank.org:act:A2ED5D61-8434-4A0F-BC5B-B496FB3DC191].

A new species of Hemigrammus (Characiformes: Characidae) from western Amazon River basin, Colombia.

A new species of Hemigrammus is described from the Amazon Basin near Leticia, Departamento Amazonas, Colombia. In common with some congeners and some Hyphessobrycon spp., the new species colour pattern lacks a humeral blotch but has a caudal-peduncle blotch. It can be distinguished from congeners with a similar colour pattern by having: a relatively deep body (30.2%-39.0% LS ), 20-24 branched anal-fin rays, 6-8 perforated scales of the lateral line, anal-fin base without a conspicuous black stripe, 3-5 maxillary teeth, maxillary teeth with 1-3 cusps, a thin longitudinal midlateral line and a well-defined oval shaped caudal blotch, extending from caudal peduncle into the lower caudal-fin rays. Comparisons with congeners and with Hyphessobrycon species sharing the same general colour pattern are presented.

Deconstructing an octogenarian misconception reveals the true Corydoras arcuatus Elwin 1938 (Siluriformes: Callichthyidae) and a new Corydoras species from the Amazon basin.

After 80 years of misidentifications, the analysis of the holotype of Corydoras arcuatus plus several non-type specimens attributed to this species allowed its recognition and also revealed a new species, both sharing the following diagnostic features: a long, arched, continuous black stripe that runs parallel to the dorsal profile of the body and extends at least from the anterior margin of the first dorsolateral body plate to the posterior portion of caudal peduncle; absence of transverse black bars on caudal fin; infraorbital 2 in contact with sphenotic and compound pterotic. In addition to these features, C. arcuatus can be distinguished from congeners by having the posterior margin of both dorsal and pectoral spines with laminar serrations directed towards their origins. The new species can be additionally distinguished from its congeners by presenting the following combination of features: ventral surface of trunk entirely or partially covered by relatively large and coalescent platelets; absence of spots or blotches on dorsal fin; and posterior margin of both dorsal and pectoral spines with serrations directed towards their tips. Finally, an identification key to all arc-striped species of Corydoras is provided.

Hyphessobrycon rheophilus, a new species from rapids of the Amazon and Orinoco river basins (Characiformes: Characidae: Stethaprioninae).

A new species from rapids of Rio Aripuanã, Rio Madeira basin, in Brazil, and from the same type of habitat in the upper Rio Negro and upper Rio Orinoco basins in Brazil, Colombia, and Venezuela is described and assigned to the genus Hyphessobrycon. The new species presents an interrupted lateral line plus a single perforated scale on caudal peduncle and a small dark blotch on dorsal procurrent caudal-fin rays, features not found in the other species of Hyphessobrycon. Comments on the phylogenetic position of the new species, its rheophilic habits, and the biogeographic implications of its distribution are presented.

Parotocinclus yaka, a new species of armored catfish (Loricariidae: Hypoptopomatinae), from the Amazon basin in Brazil.

Parotocinclus yaka is described as a new species of hypoptopomatine cascudinho from tributaries of the Rio Tiquié, tributary to the Rio Uaupés, upper Rio Negro drainage, Amazon basin, Amazonas State, Brazil. The new species is distinguished from its congeners in northeastern and southeastern Brazil by having the cheek canal plate elongated posteriorly on the ventral surface of the head and in contact with the cleithrum. Parotocinclus yaka is diagnosed from the Parotocinclus species of the Amazon, Orinoco and Guianas watersheds by having a conspicuous dark spots smaller than the pupil diameter distributed dorsally and laterally on the head; it is also differentiated from P. polyochrus (Casiquiare, Venezuela), P. longirostris (Rio Amazonas, Brazil), and P. eppleyi (Río Orinoco) by the absence of a Y-shaped light mark dorsally on the head. In addition, the absence of premaxillary and dentary accessory teeth and the presence of a Y-shaped spot on the snout distinguish the new species from P. collinsae (Essequibo River, Guyana), P. halbothi (Rio Trombetas, Brazil and Marowijne River, Suriname) and P. variola (Río Amazonas, Colombia). Parotocinclus yaka also differs from P. amazonensis (lower Amazon basin), P. aripuanensis (lower Amazon basin), P. britskii (Guyana, Suriname, eastern Venezuela, and Amapá State, Brazil), and P. dani (Rio Tapajós basin), by having more numerous oral teeth. The new species described herein is part of the group of small cascudinhos usually associated with marginal or submerged vegetation and submerged logs, of moderate current and clear transparency, found in conserved habitats in streams of the Amazon, Orinoco and Guianas rivers.

A new species of Bryconops Kner (Characiformes: Iguanodectidae) from the Rio Maicuru, lower Amazon basin, Brazil.

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.

A new Moenkhausia (Actinopterygii: Characiformes: Characidae) from the upper rio Negro basin, Brazil.

A new species of Moenkhausia is described from the upper rio Negro basin, Amazonas, Brazil. The new species is distinguished from all congeners, except M. agnesae, by presenting a color pattern characterized by the presence of two irregularly-shaped humeral blotches, and the presence of dark longitudinal stripes on the dorsal portion of the body. The new species can be readily separated from M. agnesae by presenting longitudinal stripes straight and more conspicuous dorsally, humeral blotches contacting each other, 2-3 tricuspid maxillary teeth, 32-35 lateral-line scales, and length of maxilla 45.3-51.0% in head length.

Crenicichla ploegi, a new species of pike-cichlid of the C. saxatilis group from the Rio Juruena and upper Rio Paraguai basins in Brazil, with an updated diagnosis and biogeographical comments on the group (Teleostei: Cichlidae).

Crenicichla ploegi, new species, is described based on material from the Rio Juruena (Rio Papagaio, Rio do Sangue, Rio Arinos, and Rio Juruena itself) and from tributaries of the upper Rio Paraguai (upper Rio Jauru, upper Rio Cabaçal and upper Rio Sepotuba) in Mato Grosso, Brazil. Crenicichla ploegi is the twenty-third species of the C. saxatilis group. It is distinguished from all other species of the group by the presence of dark spots and vermiculations on snout, interorbital area and dorsally on head in adults vs. dark markings absent or present only in juveniles but absent in adults, and by the presence of a deep and strongly pigmented lateral band present in both juveniles and adults, occupying a depth of 4-6 horizontal scale rows vs. lateral band narrower, occupying a depth of 2-3 horizontal scale rows, and conspicuous only in juveniles and smaller specimens, faded or absent in larger specimens. Diagnostic characteristics of the C. saxatilis group proposed in previous studies were discussed to update the diagnosis of the group, and morphological comparisons among the species included in the group, with biogeographical comments, are provided. The presence of conspicuous dark markings dorsally on the head and the presence of a prominent midlateral band are hypothesized to be paedomorphic characteristics, retained from juvenile conditions in the context of the species of the C. saxatilis group.