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Armored catfishes of the genus Eurycheilichthys are endemic to Southern Brazil and Misiones (Argentina) comprising nine species of small size, with a high degree of sympatry and species diversity distributed in two river basins. Here we use new genome-wide data to infer a species phylogeny and test species boundaries for this poorly known group. We estimate 1) the phylogenetic relationships of the species of Eurycheilichthys based on 29,350 loci in 65 individuals of nine species plus outgroups, and 2) the population structure and differentiation based on 43,712 loci and 62 individuals to estimate how geography may have acted on speciation and formation of the sympatric species groups. Analyses support the monophyly of the genus and suggest two species-inclusive clades (East and West) with high support and very recently diverged species. Western clade contains E. limulus (from upper Jacuí River basin) that is sister to Western species of the Taquari-Antas basin plus E. paucidens. The Eastern clade contains E. pantherinus (from Uruguay River basin) sister to the Eastern species of the Taquari-Antas basin E. coryphaenus, plus the central-distributed species E. planus and E. vacariensis, and the more widely-distributed species E. luisae. Eurycheilichthys luisae is not monophyletic and may contain one or more cryptic species or hybrid individuals. A stronger diversity on structure of lineages on the Taquari-Antas, when compared to upper Uruguay and Jacuí River basins, and the fact that most of the sympatrically distributed taxa have non-sister relationships suggest a scenario of mainly allopatric speciation and may indicate a more dynamic landscape with headwater capture events among these tributaries.

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Otocinclus cocama, a uniquely colored species of the loricariid catfish genus Otocinclus described solely from the type locality in the lower Ucayali River in northern Peru, is reported occurring in the Tigre River, a tributary to the Marañón River that drains a different section of the Andean Mountain range in the western Amazon. Both populations differ in the number of dark bars spanning the flanks of the body, and we investigated whether these morphotypes constitute distinct species. The body shapes of populations from the Tigre and Ucayali rivers were compared using geometric morphometrics. Although principal component analysis detected a broad overlap between populations, multivariate analysis of variance and linear driscriminat analysis revealed a subtle differentiation between the populations of the two hydrographic basins. Average body shape of the Ucayali River population tend to be slightly higher than that of the Tigre River, with the caudal peduncle stretched vertically in the Ucayali population. Multivariate regression of shape and centroid size revealed an allometric effect of 10.7% (p < 0.001), suggesting that the variation between Tigre and Ucayali populations was purely shape variation. Molecular data of coI, cytb, nd2, and 16S mitochondrial genes indicated a nucleotide diversity range from 0.001 to 0.003, and haplotypic diversity range from 0.600 ± 0.11 to 0.79 ± 0.07. The median-joining haplotype network for the concatenated matrix exhibited two divergent haplogroups related to the geographic area and separated by <10 mutational steps. The molecular species delimitation methods based on distance (automatic barcode gap discovery and assemble species by automatic partitioning) recovered two molecular lineages evolving independently, being one of the lineages formed by individuals from both populations. Tree-based methods (generalized mixed Yule coalescent and Bayesian implementation of the Poisson tree process) recovered similar topologies and supported single lineage recognition. Methods of molecular delimitation of species disclosed the high similarity between the two populations of Otocinclus cocama, further supported by the presence of old haplotypes common to both groups which could indicate that the populations still maintain gene flow. Although the morphological data reveal a subtle variation between both river basins, the molecular data suggest a weak population structuration based on hydrographic areas, but not different species lineages, therefore Otocinclus cocama is composed of a single lineage with two distinct morphotypes.

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The present work aimed to analyze the distribution of the electrosensory pores of the Daggernose Shark Carcharhinus oxyrhynchus identifying the organ's importance in the natural history of the species. By examining photographs and digital microscope videos, we found that C. oxyrhynchus possesses the highest abundance of pores among Carcharhiniformes. This suggests a well-developed electroreceptor system, which may have maximized its evolutionary success in high turbidity environments. Furthermore, as a morphologically derived species, C. oxyrhynchus comprises a more complex and specialized electrosensory system. Notably, the species exhibits ontogenetic variation in pore abundance, highlighting the importance of a high-resolution system for adults. The higher density of pores in the ventral region indicates a preference for benthic prey, despite also feeding on pelagic items. Moreover, the species has a high-resolution electrosensory system and a high density of pores in the snout, which emphasizes the importance of the elongated snout that expands the electroreception search area coverage. Evolutionary convergence was observed in the development of the electrosensory system, as C. oxyrhynchus shares characteristics of pore distribution and abundance with phylogenetically unrelated species.

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Landscape dynamics are widely thought to govern the tempo and mode of continental radiations, yet the effects of river network rearrangements on dispersal and lineage diversification remain poorly understood. We integrated an unprecedented occurrence dataset of 4,967 species with a newly compiled, time-calibrated phylogeny of South American freshwater fishes-the most species-rich continental vertebrate fauna on Earth-to track the evolutionary processes associated with hydrogeographic events over 100 Ma. Net lineage diversification was heterogeneous through time, across space, and among clades. Five abrupt shifts in net diversification rates occurred during the Paleogene and Miocene (between 30 and 7 Ma) in association with major landscape evolution events. Net diversification accelerated from the Miocene to the Recent (c. 20 to 0 Ma), with Western Amazonia having the highest rates of in situ diversification, which led to it being an important source of species dispersing to other regions. All regional biotic interchanges were associated with documented hydrogeographic events and the formation of biogeographic corridors, including the Early Miocene (c. 23 to 16 Ma) uplift of the Serra do Mar and Serra da Mantiqueira and the Late Miocene (c. 10 Ma) uplift of the Northern Andes and associated formation of the modern transcontinental Amazon River. The combination of high diversification rates and extensive biotic interchange associated with Western Amazonia yielded its extraordinary contemporary richness and phylogenetic endemism. Our results support the hypothesis that landscape dynamics, which shaped the history of drainage basin connections, strongly affected the assembly and diversification of basin-wide fish faunas.

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A new species of Sternopygus is described from the Orinoco River of Venezuela using traditional methods of morphometrics and meristics, and micro-computed tomography (micro-CT) imaging for osteological analysis. The new species is readily separated from all congeners in having broad, vertical pigment bars that extend from the mid-dorsum to the ventral margin of the pterygiophores. A similar color pattern, characterized by subtle differences in the densities and sizes of chromatophores, is also present in juveniles of S. obtusirostris from the Amazon River, juveniles of S. sabaji from rivers of the Guiana Shield, and S. astrabes from clearwater and blackwater terra firme streams of lowlands around the Guiana Shield. The new species further differs from other congeners in the Orinoco basin by having a reduced humeral pigment blotch with poorly defined margins, a proportionally smaller head, a longer body cavity, a more slender body shape in lateral profile, and in having vertical pigment bars that extend ventrally to the pterygiophores (vs. pigment saddles not reaching the pterygiophores). The description of this species raises to three the number of Sternopygus species in the Orinoco basin, and to 11 the total number of Sternopygus species.(AU)

Se describe una nueva especie de Sternopygus del río Orinoco de Venezuela utilizando métodos tradicionales de morfometría y merística, y microtomografía computarizada (micro-CT) para análisis osteológico. La nueva especie se distingue fácilmente de todos los congéneres por tener barras de pigmento verticales anchas que se extienden desde la parte media del dorso hasta el margen ventral de los pterigióforos. Un patrón de color similar, caracterizado por diferencias sutiles en las densidades y tamaños de los cromatóforos, también está presente en juveniles de S. obtusirostris del río Amazonas, juveniles de S. sabaji de ríos del Escudo Guayanés y S. astrabes de aguas claras y arroyos de tierra firme de aguas negras de las tierras bajas alrededor del Escudo Guayanés. La nueva especie se diferencia aún más de otros congéneres en la cuenca del Orinoco por tener una mancha de pigmento humeral reducida con márgenes mal definidos, una cabeza proporcionalmente más pequeña, una cavidad corporal más larga, una forma corporal más delgada en el perfil lateral y por tener barras de pigmento verticales que extenderse ventralmente a los pterigióforos (frente a las monturas de pigmentos que no llegan a los pterigióforos). La descripción de esta especie eleva a tres el número de especies de Sternopygus en la cuenca del Orinoco y a 11 el número total de especies de Sternopygus.(AU)

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A new, very distinctive species of Pareiorhaphis is described from the rio Uruguai basin, in Rio Grande do Sul State, southern Brazil. Pareiorhaphis pumila, new species, is a small bodied hypoptopomatine catfish with a maximum standard length barely reaching 50 mm. The specimens were captured from rock-bottomed habitats in various localities in the rio Ijuí basin. Despite occurring in rock-bottomed fast-flowing headwater stream tributaries as the other species of Pareiorhaphis, this is the first species collected also in the main channel of the middle stretch of a large tributary to the rio Uruguai. The new species is promptly diagnosed from all its congeners by the reduced number of anal-fin branched rays, possession of well-developed dorsal-fin spinelet, comparatively lower number of plates in median lateral series, and low number of teeth in each dentary. In addition, osteological features related to the caudal skeleton are also useful to distinguish the new species from most congeners.

Uma nova e distinta espécie de Pareiorhaphis é descrita da bacia do rio Uruguai, no estado do Rio Grande do Sul, sul do Brasil. A nova espécie é um cascudo hypoptopomatíneo de pequeno tamanho, com comprimento padrão máximo inferior a 50 mm. Os espécimes foram capturados em habitats de fundo rochoso em várias localidades da bacia do rio Ijuí. Apesar de ocorrer em córregos de cabeceira de fluxo rápido com fundo rochoso como as demais espécies de Pareiorhaphis, esta é a primeira espécie coletada também no canal principal do trecho médio de um grande afluente do rio Uruguai. A nova espécie é prontamente diagnosticada de todos os seus congêneres pelo número reduzido de raios ramificados da nadadeira anal, presença de spinelet da nadadeira dorsal bem desenvolvido, número comparativamente menor de placas na série lateral média, e baixo número de dentes em cada dentário. Além disso, características osteológicas relacionadas ao esqueleto caudal também são úteis para distinguir a nova espécie da maioria das congêneres.

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A new genus of Hypopopomatinae armored catfish is described from the northern portions of South America, namely the Amazon, Orinoco and Guianan coastal drainages. The new genus is diagnosed from all remaining hypoptopomatines by having the canal cheek plate on the ventral surface of the head posteriorly elongated and contacting the cleithrum, in addition to other features that distinguish the new genus from specific genera. Five new species are described and 18 species currently allocated in Parotocinclus, Hisonotus, and Curculionichthys are transferred to the new genus and rediagnosed. Parotocinclus amazonensis and P. aripuanensis are considered junior synonyms of P. britskii. The secondary sexual dimorphism of the members of the new genus is detailed and illustrated. Morphological characters are used to delimit four phenotypic groups of species that might have phylogenetic significance, which still have to be properly tested. A key to the species is offered and diagnoses, illustrations, and distribution maps are provided for all species.(AU)

Um novo gênero de cascudo da subfamília Hypopopomatinae é descrito das porções do norte da América do Sul, a saber, as drenagens costeiras da Amazônia, Orinoco e Guiana. O novo gênero é diagnosticado de todos os demais hypoptopomatineos por possuir a placa com canal da bochecha na superfície ventral da cabeça, alongada posteriormente e em contato com o cleitro, além de outras características que distinguem o novo gênero de gêneros específicos. Cinco novas espécies são descritas e 18 espécies atualmente alocadas em Parotocinclus, Hisonotus e Curculionichthys são transferidas para o novo gênero e rediagnosticadas. Parotocinclus amazonensis e P. aripuanensis são considerados sinônimos juniores de P. britskii. O dimorfismo sexual secundário dos membros do novo gênero é detalhado e ilustrado. Caracteres morfológicos são usados para delimitar quatro grupos fenotípicos de espécies que podem ter significado filogenético, que ainda precisam ser devidamente testados. Uma chave para as espécies é apresentada e diagnoses, ilustrações e mapas de distribuição são fornecidos para todas as espécies.(AU)

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We present a combined molecular and morphological phylogenetic analysis of the Loricariinae, with emphasis on the Harttiini (Cteniloricaria, Harttia, and Harttiella) and Farlowellini (Aposturisoma, Farlowella, Lamontichthys, Pterosturisoma, Sturisoma, and Sturisomatichthys). Character sampling comprised seven molecular markers (the mitochondrial Cytb, nd2, 12S and 16S, and the nuclear MyH6, RAG1 and RAG2) and 196 morphological characters. A total of 1,059 specimens, and 159 tissue samples were analized, representing 100 species. A Bayesian Inference analysis was performed using the concatenated data matrix, which is comprised of 6,819 characters. The Loricariinae were found to comprise the tribes (Hartiini (Loricariini, Farlowellini)), the latter two elevated from subtribes. A Maximum Parsimony analysis was also performed using the same data matrix in order to reveal phenotypical synapomorphies to diagnose each clade. Two MP trees were found with a length of 14,704 steps, consistency index of 0.29 and retention index of 0.61, which were summarized in a strict consensus tree. Harttiini includes (Harttiella (Cteniloricaria, Harttia), and Farlowellini includes (Lamontichthys (Pterosturisoma (Sturisoma (Sturisomatichthys, Farlowella)))). Aposturisoma was recovered nested within Farlowella and is synonymyzed to the latter. Sturisoma was corroborated as strictly cis-Andean, while Sturisomatichthys encompasses, besides the valid species already included in the genus, the trans-Andean species once belonging to Sturisoma sensu lato. Identification keys and phylogenetic diagnoses of family-group taxa and genera of both the Harttiini and the Farlowellini are provided.

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Two new species of heptapterid catfish genus Cetopsorhamdia are described from close localities in western Brazil, at Chapada dos Parecis, an area with extremely high level of endemism. One species is from the upper Rio Madeira system, Rondônia State, and the other from the upper Rio Tapajós system, Mato Grosso State. The two species are diagnosed, among several other features, by their markedly distinctive color patterns, with the former having well-defined quadrangular marks in trunk flanks while the latter bearing irregular, vertical bars along the trunk. The monophyly of Cetopsorhamdia is discussed, with two putative synapomorphies being proposed to support the genus. Potentially informative morphological characters to resolve the internal relationships of the genus are presented and discussed. Despite the striking external differences between the two species herein described, they are found to likely form a clade.(AU)

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Freshwater ecosystems provide irreplaceable services for both nature and society. The quality and quantity of freshwater affect biogeochemical processes and ecological dynamics that determine biodiversity, ecosystem productivity, and human health and welfare at local, regional and global scales. Freshwater ecosystems and their associated riparian habitats are amongst the most biologically diverse on Earth, and have inestimable economic, health, cultural, scientific and educational values. Yet human impacts to lakes, rivers, streams, wetlands and groundwater are dramatically reducing biodiversity and robbing critical natural resources and services from current and future generations. Freshwater biodiversity is declining rapidly on every continent and in every major river basin on Earth, and this degradation is occurring more rapidly than in terrestrial ecosystems. Currently, about one third of all global freshwater discharges pass through human agricultural, industrial or urban infrastructure. About one fifth of the Earth's arable land is now already equipped for irrigation, including all the most productive lands, and this proportion is projected to surpass one third by midcentury to feed the rapidly expanding populations of humans and commensal species, especially poultry and ruminant livestock. Less than one fifth of the world's preindustrial freshwater wetlands remain, and this proportion is projected to decline to under one tenth by midcentury, with imminent threats from water transfer megaprojects in Brazil and India, and coastal wetland drainage megaprojects in China. The Living Planet Index for freshwater vertebrate populations has declined to just one third that of 1970, and is projected to sink below one fifth by midcentury. A linear model of global economic expansion yields the chilling prediction that human utilization of critical freshwater resources will approach one half of the Earth's total capacity by midcentury. Although the magnitude and growth of the human freshwater footprint are greater than is generally understood by policy makers, the news media, or the general public, slowing and reversing dramatic losses of freshwater species and ecosystems is still possible. We recommend a set of urgent policy actions that promote clean water, conserve watershed services, and restore freshwater ecosystems and their vital services. Effective management of freshwater resources and ecosystems must be ranked amongst humanity's highest priorities.

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Cteniloricaria is a genus of Neotropical armored catfishes belonging to the Loricariinae, currently including two valid species: C. platystoma and C. napova. Cteniloricaria platystoma is presently recorded across the main coastal drainages of the Guiana Shield, from the Sinnamary River, French Guiana, to the Essequibo River basin, Guyana, and is considered to be restricted to the region. Cteniloricaria napova is only known from its type locality at the headwaters of the Paru de Oeste River, Amazon basin, Sipaliwini Savannah, Trio Amerindian territory in Suriname, close to the Brazilian border. Based on a specimen of C. napova, captured in the Cuminapanema River, a tributary to the Curuá River, within Brazilian territory, the geographic distribution of the species and the genus is extended, representing the first record of Cteniloricaria in Brazil. The genus shows a disjoint distribution, and divergence between populations in the north-flowing coastal rivers of the Guianas and the south-flowing Amazon tributaries, and more recent headwater capture between south-flowing Amazon tributaries, may have played a key role in shaping its current distribution. Illustrations, diagnostic characters, morphometrics, description of the habitat where the new specimen was captured, extinction risk assessment, and a discussion of the distribution of the genus are provided.(AU)

Cteniloricaria é um gênero de cascudos neotropicais pertencente à Loricariinae, atualmente incluindo duas espécies válidas: C. platystoma e C. napova. Atualmente, C. platystoma é registrada nas principais drenagens costeiras do Escudo das Guianas, desde o rio Sinnamary, na Guiana Francesa, até a bacia do rio Essequibo, Guyana, sendo considerada restrita à região. Cteniloricaria napova é conhecida unicamente por sua localidade-tipo nas cabeceiras do rio Paru de Oeste, bacia Amazônica, Savana Sipaliwini, território indígena de Trio, no Suriname, próximo à fronteira com o Brasil. Com base em um espécime de C. napova, capturado no rio Cuminapanema, afluente do rio Curuá, em território brasileiro, a distribuição geográfica da espécie e do gênero se estende até a bacia do rio Curuá, representando o primeiro registro de Cteniloricaria no Brasil. O gênero apresenta uma distribuição disjunta e, eventos como divergência entre as populações dos rios costeiros das Guianas e nos afluentes do Amazonas, e mais recente captura de cabeceiras entre os afluentes do Amazonas, podem ter desempenhado um papel fundamental em sua distribuição atual. São fornecidos ilustrações, caracteres diagnósticos, morfometria, descrição do habitat onde o novo espécime foi capturado, avaliação do risco de extinção e uma discussão sobre a distribuição do gênero.(AU)

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Abstract Two new species of heptapterid catfish genus Cetopsorhamdia are described from close localities in western Brazil, at Chapada dos Parecis, an area with extremely high level of endemism. One species is from the upper Rio Madeira system, Rondônia State, and the other from the upper Rio Tapajós system, Mato Grosso State. The two species are diagnosed, among several other features, by their markedly distinctive color patterns, with the former having well-defined quadrangular marks in trunk flanks while the latter bearing irregular, vertical bars along the trunk. The monophyly of Cetopsorhamdia is discussed, with two putative synapomorphies being proposed to support the genus. Potentially informative morphological characters to resolve the internal relationships of the genus are presented and discussed. Despite the striking external differences between the two species herein described, they are found to likely form a clade.

RESUMO

The IUCN Red List (RL) provides high-quality conservation assessments for individual species, yet the rate and scale of environmental deterioration globally challenges the conservation community to develop expedited methods for risk assessment. Here we compare threat assessments for 3,001 species of Neotropical freshwater fishes (NFF) in the IUCN-RL using readily accessible data types as proxies for extinction risk: geographic range, elevation, and species publication date. Furthermore, using geographic and taxonomic data alone, we generated preliminary conservation assessments for 2,334 NFF species currently awaiting IUCN assessment, identifying an additional 671 NFF species as potentially threatened. This number of potentially threatened species represents an increase of 59% over the number of species currently assigned to threat categories by the IUCN-RL. These results substantially expand the number of threatened NFF species from 422 currently on the IUCN RL to 1,093 species as threatened or potentially threatened, representing about 18% of all NFF species. Extinction risk is greater in species with smaller geographic ranges, which inhabit upland rivers, and which were described more recently. We propose the Central and Southern Andes, and Eastern Guiana Shield as priorities in the upcoming IUCN RL assessment of NFF species conservation risk.(AU)

A Lista Vermelha (IUCN) fornece avaliações precisas sobre status de conservação das espécies, porém a taxa e escala de deterioração ambiental desafia a comunidade conservacionista a desenvolver métodos rápidos para avaliações de riscos de extinção. Aqui, comparamos as avaliações da IUCN para 3.001 espécies de peixes dulcícolas neotropicais com dados facilmente acessíveis de risco de extinção: extensão de ocorrências, altitude e data de publicação das espécies. Além disso, usando apenas dados geográficos e taxonômicos, geramos avaliações preliminares de conservação para 2.334 espécies de peixes neotropicais aguardando avaliação da IUCN, e identificamos 671 espécies adicionais como potencialmente ameaçadas. Este número de espécies potencialmente ameaçadas representa um aumento de 59% em relação aquelas classificadas nas categorias de ameaça pela IUCN. Estes resultados expandem o número de espécies ameaçadas segundo a IUCN de 422 para 1.093 espécies ameaçadas ou potencialmente ameaçadas, representando cerca de 18% das espécies de peixes neotropicais. O risco de extinção é maior para espécies com distribuições geográficas restritas, que habitam rios de terras altas e que foram descritas mais recentemente. Sugerimos a região Central e Meridional do Andes e o Escudo das Guianas Orientais como prioridades para as próximas avaliações da IUCN sobre a conservação das espécies de peixes dulcícolas neotropicais.(AU)

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Abstract Two new species of heptapterid catfish genus Cetopsorhamdia are described from close localities in western Brazil, at Chapada dos Parecis, an area with extremely high level of endemism. One species is from the upper Rio Madeira system, Rondônia State, and the other from the upper Rio Tapajós system, Mato Grosso State. The two species are diagnosed, among several other features, by their markedly distinctive color patterns, with the former having well-defined quadrangular marks in trunk flanks while the latter bearing irregular, vertical bars along the trunk. The monophyly of Cetopsorhamdia is discussed, with two putative synapomorphies being proposed to support the genus. Potentially informative morphological characters to resolve the internal relationships of the genus are presented and discussed. Despite the striking external differences between the two species herein described, they are found to likely form a clade.

RESUMO

The IUCN Red List (RL) provides high-quality conservation assessments for individual species, yet the rate and scale of environmental deterioration globally challenges the conservation community to develop expedited methods for risk assessment. Here we compare threat assessments for 3,001 species of Neotropical freshwater fishes (NFF) in the IUCN-RL using readily accessible data types as proxies for extinction risk: geographic range, elevation, and species publication date. Furthermore, using geographic and taxonomic data alone, we generated preliminary conservation assessments for 2,334 NFF species currently awaiting IUCN assessment, identifying an additional 671 NFF species as potentially threatened. This number of potentially threatened species represents an increase of 59% over the number of species currently assigned to threat categories by the IUCN-RL. These results substantially expand the number of threatened NFF species from 422 currently on the IUCN RL to 1,093 species as threatened or potentially threatened, representing about 18% of all NFF species. Extinction risk is greater in species with smaller geographic ranges, which inhabit upland rivers, and which were described more recently. We propose the Central and Southern Andes, and Eastern Guiana Shield as priorities in the upcoming IUCN RL assessment of NFF species conservation risk.(AU)

A Lista Vermelha (IUCN) fornece avaliações precisas sobre status de conservação das espécies, porém a taxa e escala de deterioração ambiental desafia a comunidade conservacionista a desenvolver métodos rápidos para avaliações de riscos de extinção. Aqui, comparamos as avaliações da IUCN para 3.001 espécies de peixes dulcícolas neotropicais com dados facilmente acessíveis de risco de extinção: extensão de ocorrências, altitude e data de publicação das espécies. Além disso, usando apenas dados geográficos e taxonômicos, geramos avaliações preliminares de conservação para 2.334 espécies de peixes neotropicais aguardando avaliação da IUCN, e identificamos 671 espécies adicionais como potencialmente ameaçadas. Este número de espécies potencialmente ameaçadas representa um aumento de 59% em relação aquelas classificadas nas categorias de ameaça pela IUCN. Estes resultados expandem o número de espécies ameaçadas segundo a IUCN de 422 para 1.093 espécies ameaçadas ou potencialmente ameaçadas, representando cerca de 18% das espécies de peixes neotropicais. O risco de extinção é maior para espécies com distribuições geográficas restritas, que habitam rios de terras altas e que foram descritas mais recentemente. Sugerimos a região Central e Meridional do Andes e o Escudo das Guianas Orientais como prioridades para as próximas avaliações da IUCN sobre a conservação das espécies de peixes dulcícolas neotropicais.(AU)

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Cteniloricaria is a genus of Neotropical armored catfishes belonging to the Loricariinae, currently including two valid species: C. platystoma and C. napova. Cteniloricaria platystoma is presently recorded across the main coastal drainages of the Guiana Shield, from the Sinnamary River, French Guiana, to the Essequibo River basin, Guyana, and is considered to be restricted to the region. Cteniloricaria napova is only known from its type locality at the headwaters of the Paru de Oeste River, Amazon basin, Sipaliwini Savannah, Trio Amerindian territory in Suriname, close to the Brazilian border. Based on a specimen of C. napova, captured in the Cuminapanema River, a tributary to the Curuá River, within Brazilian territory, the geographic distribution of the species and the genus is extended, representing the first record of Cteniloricaria in Brazil. The genus shows a disjoint distribution, and divergence between populations in the north-flowing coastal rivers of the Guianas and the south-flowing Amazon tributaries, and more recent headwater capture between south-flowing Amazon tributaries, may have played a key role in shaping its current distribution. Illustrations, diagnostic characters, morphometrics, description of the habitat where the new specimen was captured, extinction risk assessment, and a discussion of the distribution of the genus are provided.(AU)

Cteniloricaria é um gênero de cascudos neotropicais pertencente à Loricariinae, atualmente incluindo duas espécies válidas: C. platystoma e C. napova. Atualmente, C. platystoma é registrada nas principais drenagens costeiras do Escudo das Guianas, desde o rio Sinnamary, na Guiana Francesa, até a bacia do rio Essequibo, Guyana, sendo considerada restrita à região. Cteniloricaria napova é conhecida unicamente por sua localidade-tipo nas cabeceiras do rio Paru de Oeste, bacia Amazônica, Savana Sipaliwini, território indígena de Trio, no Suriname, próximo à fronteira com o Brasil. Com base em um espécime de C. napova, capturado no rio Cuminapanema, afluente do rio Curuá, em território brasileiro, a distribuição geográfica da espécie e do gênero se estende até a bacia do rio Curuá, representando o primeiro registro de Cteniloricaria no Brasil. O gênero apresenta uma distribuição disjunta e, eventos como divergência entre as populações dos rios costeiros das Guianas e nos afluentes do Amazonas, e mais recente captura de cabeceiras entre os afluentes do Amazonas, podem ter desempenhado um papel fundamental em sua distribuição atual. São fornecidos ilustrações, caracteres diagnósticos, morfometria, descrição do habitat onde o novo espécime foi capturado, avaliação do risco de extinção e uma discussão sobre a distribuição do gênero.(AU)

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Epactionotus species are known for inhabiting the rocky-bottom stretches of fast-flowing rivers in a limited geographic area along the Atlantic coast of southern Brazil. These species are endemic to single coastal river drainages (two neighbouring drainages for Epactionotus bilineatus) isolated from each other by the coastal lacustrine environments or the Atlantic Ocean. E. bilineatus is from the Maquiné and Três Forquilhas River basins, both tributaries of the Tramandaí River system, whereas E. itaimbezinho is endemic to the Mampituba River drainage and Epactionotus gracilis to the Araranguá River drainage. Recent fieldwork in the Atlantic coastal drainages of southern Brazil revealed new populations in the Urussanga, Tubarão, d'Una and Biguaçu River drainages. Iterative species delimitation using molecular data (cytochrome c oxidase subunit I) and morphology (morphometrics and meristics) was applied to evaluate species recognition of isolated populations. With regard to new data, the genus was re-diagnosed, the status of Epactionotus species/populations was re-evaluated, formerly described species were supported and population structure was recognized. As for the newly discovered populations, both morphological and molecular data strongly support the population from the Biguaçu River drainage, in Santa Catarina State, as a new species. Molecular data revealed strong per-basin population structure, which may be related to species habitat specificity and low or no dispersal among drainages.

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RESUMO

Pareiorhaphis hystrix is a widely distributed species, occurring in the upper and middle Uruguay River and in the Taquari River basin, Patos Lagoon system, southern Brazil. Morphological variation has been detected throughout the distribution of P. hystrix, and this work seeks to test the conspecific nature of populations in several occurrence areas. Specimens from six areas in the Uruguay River basin and three in the Taquari River basin were compared. Variance analysis (ANOVA) was performed for the meristic data, and Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were conducted for morphometric data. Molecular analyses used coI, cytb, 12S and 16S mitochondrial genes, examining nucleotide diversity, haplotype diversity, genetic distance, and delimitation of possible multiple species through the Generalized Mixed Yule Coalescent (GMYC) method. Phylogenetic relationships of studied populations were also investigated through Bayesian inference. While PCA indicated a tendency of overlap between areas, ANOVA and LDA detected a subtle differentiation between populations from the two hydrographic basins. Yet, both latter analyses recovered the population from Pelotas River, a tributary to Uruguay River, as more similar to populations from Taquari River, which is congruent to morphological observations of anterior abdominal plates. The molecular data indicated a nucleotide diversity lower than the haplotypic diversity, suggestive of recent expansion. The concatenated haplotype network points to slight differentiation between areas, with each locality presenting unique and non-shared haplotypes, although with few mutational steps in general. The species delimitation by coalescence analysis suggested the presence of a variable number of OTUs depending on the inclusion or exclusion of an outgroup. In general, the morphological data suggest a subtle variation by river basin, while the genetic data indicates a weak population structuration by hydrographic areas, especially the Chapecó and Passo Fundo rivers. However, there is still not enough differentiation between the specimens to suggest multiple species. The iterative analyses indicate that Pareiorhaphis hystrix is composed of a single, although variable, species.

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RESUMO

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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RESUMO

This study aims to investigate relationships between species traits and publication date in the weakly electric osteoglossiform Mormyroidea (African knifefish and elephantfishes) and the ostariophysan Gymnotiformes (Neotropical knifefishes). It is investigated whether body size and geographic distribution area are correlated with publication date and whether extinction risk differs between both phylogenetically distant and geographically isolated clades. Statistical modelling indicates that the number of new species described annually is stable in mormyroids and clearly increasing in gymnotiforms. Best-fitting generalised linear models (GLM) indicate that the newly discovered species are more often of small-bodied, predominantly narrowly distributed and more likely to be threatened with extinction. These characteristics are more pronounced in mormyroids when compared with gymnotiforms, suggesting that some African electric fishes may live an ephemeral existence after formal description. Despite taxonomic work has been more intense in the Neotropics than in Africa in the recent decades, there is evidence that the African continent represents the next frontier of species descriptions. Taxonomic studies are fundamental for the understanding of richness and distribution and hence extinction risk assessment and conservation, of these remarkable convergent fish clades.

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