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Ichthyological surveys have traditionally been conducted using whole-specimen, capture-based sampling with varied, but conventional fishing gear. Recently, environmental DNA (eDNA) metabarcoding has emerged as a complementary, and possible alternative, approach to whole-specimen methodologies. In the tropics, where much of the diversity remains undescribed, vast reaches continue unexplored, and anthropogenic activities are constant threats; there have been few eDNA attempts for ichthyological inventories. We tested the discriminatory power of eDNA using MiFish primers with existing public reference libraries and compared this with capture-based methods in two distinct ecosystems in the megadiverse Amazon basin. In our study, eDNA provided an accurate snapshot of the fishes at higher taxonomic levels and corroborated its effectiveness to detect specialized fish assemblages. Some flaws in fish metabarcoding studies are routine issues addressed in natural history museums. Thus, by expanding their archives to include eDNA and adopting a series of initiatives linking collection-based research, training and outreach, natural history museums can enable the effective use of eDNA to survey Earth’s hotspots of biodiversity before taxa go extinct. Our project surveying poorly explored rivers and using DNA vouchered archives to build metabarcoding libraries for Neotropical fishes can serve as a model of this protocol.

The Amazon has the highest richness of freshwater organisms in the world, which has led to a multitude of hypotheses on the mechanisms that generated this biodiversity. However, most of these hypotheses focus on the spatial distance of populations, a framework that fails to provide an explicit mechanism of speciation. Ecological conditions in Amazon freshwaters can be strikingly distinct, as it has been recognized since Alfred Russel Wallace’s categorization into black, white, and blue (= clear) waters. Water types reflect differences in turbidity, dissolved organic matter, electrical conductivity, pH, amount of nutrients and lighting environment, characteristics that directly affect the sensory abilities of aquatic organisms. Since natural selection drives evolution of sensory systems to function optimally according to environmental conditions, the sensory systems of Amazon freshwater organisms are expected to vary according to their environment. When differences in sensory systems affect chances of interbreeding between populations, local adaptations may result in speciation. Here, we briefly present the limnologic characteristics of Amazonian water types and how they are expected to influence photo-, chemical-, mechano-, and electro-reception of aquatic organisms, focusing on fish. We put forward that the effect of different water types on the adaptation of sensory systems is an important mechanism that contributed to the evolution of fish diversity. We point toward underexplored research perspectives on how divergent selection may act on sensory systems and thus contribute to the origin and maintenance of the biodiversity of Amazon aquatic environments.

To better understand the fish fauna of Amazonian streams, we assessed small streams in a landscape of forest fragments and savannah in the region of the lower Tapajós River, Brazil. We sampled the fish fauna using a well-tested active capture method during two dry seasons (October 2006 and 2018) and one rainy season (March to May 2018). Species richness was calculated using an abundance matrix and first-order jackknife estimator. Using qualitative and quantitative data, we present a cluster analysis in which each stream corresponds to a sampling unit. We collected 6,094 individuals of 43 species distributed in six orders. The sampling effort represents 73% of the estimated richness (58.69 ± 7.65). The most abundant species were Copella nattereri, Iguanodectes variatus and Laimosemion dibaphus that together represent almost half of the total sample (48.7%). The most frequent species were Aequidens epae, Helogenes marmoratus and Laimosemion dibaphus, which were collected in 11 of the 13 sampled streams. This is the first fish fauna list for small-order streams of savannah and forest fragments landscape in Amazonian Brazil. The richness of fish and the presence of many rare species underscore the contribution of small streams to the regional fish fauna composition, even in dynamic and spatially restricted landscapes. Resumo: Com o objetivo de aprimorar o conhecimento científico sobre a ocorrência da ictiofauna de riachos na Amazônia, acessamos pequenos riachos em uma paisagem composta por fragmentos florestais e savana, na região do baixo rio Tapajós. Amostramos a fauna de peixes com um método bem testado de captura ativa em duas estações secas, outubro de 2006 e 2018 e em uma estação chuvosa de março a maio de 2018. A riqueza de espécies foi calculada a partir da matriz de abundância com o estimador jackknife de primeira ordem. Usando dados qualitativos e quantitativos, apresentamos uma análise de agrupamento, onde cada riacho corresponde a uma unidade amostral. Coletamos 6094 indivíduos, de 43 espécies distribuídas em seis ordens. O esforço de amostragem representou 73% da riqueza estimada (58,69 ± 7,65). As espécies mais abundantes foram Copella nattereri, Iguanodectes variatus e Laimosemion dibaphus, representando em conjunto quase a metade do total amostrado (48,7%). As espécies mais frequentes foram Aequidens epae, Helogenes marmoratus e Laimosemion dibaphus, coletadas em 11 dos 13 riachos amostrados. Esta é a primeira lista de peixes de pequenos riachos em savana e fragmentos florestais da Amazônia brasileira. A riqueza de peixes e a presença de muitas espécies raras ressaltam a contribuição de riachos de pequena ordem para a composição regional da fauna de peixes, mesmo em paisagens dinâmicas e espacialmente restritas.

To determine the effect of rivers, environmental conditions, and isolation by distance on the distribution of species in Amazonia. Location: Brazilian Amazonia. Time period: Current. Major taxa studied: Birds, fishes, bats, ants, termites, butterflies, ferns + lycophytes, gingers and palms. We compiled a unique dataset of biotic and abiotic information from 822 plots spread over the Brazilian Amazon. We evaluated the effects of environment, geographic distance and dispersal barriers (rivers) on assemblage composition of animal and plant taxa using multivariate techniques and distance- and raw-data-based regression approaches. Environmental variables (soil/water), geographic distance, and rivers were associated with the distribution of most taxa. The wide and relatively old Amazon River tended to determine differences in community composition for most biological groups. Despite this association, environment and geographic distance were generally more important than rivers in explaining the changes in species composition. The results from multi-taxa comparisons suggest that variation in community composition in Amazonia reflects both dispersal limitation (isolation by distance or by large rivers) and the adaptation of species to local environmental conditions. Larger and older river barriers influenced the distribution of species. However, in general this effect is weaker than the effects of environmental gradients or geographical distance at broad scales in Amazonia, but the relative importance of each of these processes varies among biological groups.

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.

Consider both water and land When designing terrestrial reserves, it is common to consider the needs of species and systems from a terrestrial perspective, with an assumption that any freshwater systems will benefit as well. Leal et al. tested this assumption by analyzing data from two locations in the Brazilian Amazon and found that it is far from accurate: Terrestrial systems confer little benefit to freshwater systems (see the Perspective by Abell and Harrison). However, the authors also found that integrating the needs of freshwater species into overall reserve planning increased freshwater benefits by 600% while only decreasing terrestrial outcomes by 1%. They argue that reserve planning must take freshwater systems into account if they are to protect across both realms. Science , this issue p. 117 ; see also p. 38

Despite conservation of the diploid number, a huge diversity in karyotype formulae is found in the Ancistrini tribe (Loricariidae, Hypostominae). However, the lack of cytogenetic data for many groups impairs a comprehensive understanding of the chromosomal relationships and the impact of chromosomal changes on their evolutionary history. Here, we present for the first time the karyotype of Panaqolus tankei Crameramp; Sousa, 2016. We focused on the chromosomal characterization, using conventional and molecular cytogenetic techniques to unravel the evolutionary trends of this tribe. P. tankei, as most species of its sister group Pterygoplichthini, also possessess a conserved diploid number of 52 chromosomes. We observed heterochromatin regions in the centromeres of many chromosomes; pairs 5 and 6 presented interstitial heterochromatin regions, whereas pairs 23 and 24 showed extensive heterochromatin regions in their q arms. In situ localization of 18S rDNA showed hybridization signals correlating with the nucleolus organizer regions, which are located in the q arms of pair 5. However, the 5S rDNA was detected in the centromeric and terminal regions of the q arms of pair 8. (TTAGGG)n hybridized only in the terminal regions of all chromosomes. Microsatellite in situ localization showed divergent patterns, (GA)15 repeated sequences were restricted to the terminal regions of some chromosomes, whereas (AC)15 and (GT)15 showed a scattered hybridization pattern throughout the genome. Intraspecific comparative genomic hybridization was performed on the chromosomes of P. tankei to verify the existence of sex-specific regions. The results revealed only a limited number of overlapping hybridization signals, coinciding with the heterochromatin in centromeric regions without any sex-specific signals in both males and females. Our study provides a karyotype description of P. tankei, highlighting extensive differences in the karyotype formula, the heterochromatin regions, and sites of 5S and 18S rDNA, as compared with data available for the genus.

1. Agricultural expansion and intensification are major threats to tropical biodiversity. In addition to the direct removal of native vegetation, agricultural expansion often elicits other human-induced disturbances, many of which are poorly addressed by existing environmental legislation and conservation programmes. This is particularly true for tropical freshwater systems, where there is considerable uncertainty about whether a legislative focus on protecting riparian vegetation is sufficient to conserve stream fauna. 2. To assess the extent to which stream fish are being effectively conserved in agricultural landscapes, we examined the spatial distribution of assemblages in river basins to identify the relative importance of human impacts at instream, riparian and catchment scales, in shaping observed patterns. We used an extensive dataset on the ecological condition of 83 low-order streams distributed in three river basins in the eastern Brazilian Amazon. 3. We collected and identified 24,420 individual fish from 134 species. Multiplicative diversity partitioning revealed high levels of compositional dissimilarity (DS) among stream sites (DS = 0.74 to 0.83) and river basins (DS = 0.82), due mainly to turnover (77.8% to 81.8%) rather than nestedness. The highly heterogeneous fish faunas in small Amazonian streams underscore the vital importance of enacting measures to protect forests on private lands outside of public protected areas. 4. Instream habitat features explained more variability in fish assemblages (15%–19%) than riparian (2%–12%), catchment (4%–13%) or natural covariates (4%–11%). Although grouping species into functional guilds allowed us to explain up to 31% of their abundance (i.e. for nektonic herbivores), individual riparian - and catchment - scale predictor variables that are commonly a focus of environmental legislation explained very little of the observed variation (partial R2 values mostly

Diversity gradients are observed in various groups of organisms. For fishes in streams, the Water-Energy, Productivity and Temporal Heterogeneity hypotheses are considered the best combination to explain richness patterns. The relationship between species diversity and the variables that represent the hypotheses are generally considered linear and stationary, that is, there is equal relation of cause and effect along an entire geographical extension. The assumption of stationarity has not been tested or even observed in diversity gradients, thus producing imprecise models. Therefore, our goal is to quantify stationarity in the existing relationships between the ichthyofauna of streams and the Water-Energy, Productivity and Temporal Heterogeneity hypotheses using a Geographically Weighted Regression – GWR. In the proposed model, there is conspicuous absence of stationarity between fish species richness and the tested hypotheses. Furthermore, water-energy dynamics were observed as a possible metabolic restriction mechanism acting on the community structuring of stream fishes. This mechanism divides the fish fauna from the studied Brazilian watercourses in two regions: i) Amazonian, characterized by a stable climate and populations with little resistance to thermal variation; and ii) Central, featured by greater ranges of temperature and fish populations resistant to thermal variation.

The Amazon Basin is an unquestionable biodiversity hotspot, containing the highest freshwater biodiversity on earth and facing off a recent increase in anthropogenic threats. The current knowledge on the spatial distribution of the freshwater fish species is greatly deficient in this basin, preventing a comprehensive understanding of this hyper-diverse ecosystem as a whole. Filling this gap was the priority of a transnational collaborative project, i.e. the AmazonFish project - https://www.amazon-fish.com/. Relying on the outputs of this project, we provide the most complete fish species distribution records covering the whole Amazon drainage. The database, including 2,406 validated freshwater native fish species, 232,936 georeferenced records, results from an extensive survey of species distribution including 590 different sources (e.g. published articles, grey literature, online biodiversity databases and scientific collections from museums and universities worldwide) and field expeditions conducted during the project. This database, delivered at both georeferenced localities (21,500 localities) and sub-drainages grains (144 units), represents a highly valuable source of information for further studies on freshwater fish biodiversity, biogeography and conservation., Measurement(s)Diversity • Fish • spatial patternTechnology Type(s)digital curationFactor Type(s)geographic locationSample Characteristic - OrganismfishSample Characteristic - Environmentdrainage basinSample Characteristic - LocationAmazon Basin Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.11920800

Conserving freshwater habitats and their biodiversity in the Amazon Basin is a growing challenge in the face of rapid anthropogenic changes. We used the most comprehensive fish-occurrence database available (2355 valid species; 21,248 sampling points) and 3 ecological criteria (irreplaceability, representativeness, and vulnerability) to identify biodiversity hotspots based on 6 conservation templates (3 proactive, 1 reactive, 1 representative, and 1 balanced) to provide a set of alternative planning solutions for freshwater fish protection in the Amazon Basin. We identified empirically for each template the 17% of sub-basins that should be conserved and performed a prioritization analysis by identifying current and future (2050) threats (i.e., degree of deforestation and habitat fragmentation by dams). Two of our 3 proactive templates had around 65% of their surface covered by protected areas; high levels of irreplaceability (60% of endemics) and representativeness (71% of the Amazonian fish fauna); and low current and future vulnerability. These 2 templates, then, seemed more robust for conservation prioritization. The future of the selected sub-basins in these 2 proactive templates is not immediately threatened by human activities, and these sub-basins host the largest part of Amazonian biodiversity. They could easily be conserved if no additional threats occur between now and 2050.Puntos Calientes de Diversidad de Peces de Agua Dulce para las Prioridades de Conservación en la Cuenca del Amazonas Resumen Cada día, la conservación de los hábitats de agua dulce y su biodiversidad en la cuenca del Amazonas es un reto creciente de cara a los rápidos cambios antropogénicos. Usamos la base de datos de presencia de peces más completa que existe (2,355 especies válidas; 21,248 puntos de muestreo) y tres criterios ecológicos (carácter irremplazable, representatividad y vulnerabilidad) para identificar los puntos calientes de biodiversidad con base en seis patrones de conservación (tres proactivos, uno reactivo, uno representativo y uno balanceado) y así proporcionar un conjunto de soluciones alternativas para la planeación de la protección de peces de agua dulce en la cuenca del Amazonas. Identificamos para cada patrón de manera empírica el 17% de las subcuencas que deberían conservarse y realizamos un análisis de priorización identificando amenazas actuales y a futuro (2050) (es decir, grado de deforestación y fragmentación del hábitat causado por presas). Dos de nuestros tres patrones proactivos tuvieron alrededor del 65% de su superficie cubierta por áreas protegidas; niveles altos de carácter irremplazable (60% de especies endémicas) y de representatividad (71% de la fauna ictiológica del Amazonas); y una vulnerabilidad baja actual y a futuro. Entonces, estos dos patrones parecen estar más completos para la priorización de la conservación. El futuro de las subcuencas en estos dos patrones proactivos no está amenazado por las actividades humanas a corto plazo. Además, estas subcuencas albergan la mayor parte de la biodiversidad amazónica. Se podrían conservar fácilmente si ninguna amenaza adicional sucede entre ahora y el 2050.

The Amazon basin has a freshwater fish diversity comparable to a tropical sea. Although many Amazonian fish species are popular ornamental fish across the world, the ecology of most species in their natural habitat remains poorly known (van der Sleen and Albert 2017). We report on shoaling behavior inPlatydoras hancockiiin a floodplain forest of the middle Rio Negro, Brazil. As the shoal consisted of only adult males, whereas gravid females were caught individually in nearby areas, we hypothesize that this aggregation may relate to spawning. Moreover, considering thatPlatydoras hancockiiis capable of producing sounds, it is possible that these aggregations entail the formation of a chorus-like call with the function of attracting females from a larger area.

A recent boom in hydroelectric development in the world's most diverse tropical river basins is currently threatening aquatic biodiversity on an unprecedented scale. Among the most controversial of these projects is the Belo Monte Hydroelectric Complex (BMHC) on the Xingu River, the Amazon's largest clear-water tributary. The design of the BMHC creates three distinctly altered segments: a flooded section upstream of the main dam, a middle section between the dam and the main powerhouse that will be dewatered, and a downstream section subject to flow alteration from powerhouse discharge. This region of the Xingu is notable for an extensive series of rapids known as the Volta Grande that hosts exceptional levels of endemic aquatic biodiversity; yet, patterns of temporal and spatial variation in community composition within this highly threatened habitat are not well documented. We surveyed fish assemblages within rapids in the three segments impacted by the BMHC prior to hydrologic alteration, and tested for differences in assemblage structure between segments and seasons. Fish species richness varied only slightly between segments, but there were significant differences in assemblage structure between segments and seasons. Most of the species thought to be highly dependent on rapids habitat, including several species listed as threatened in Brazil, were either restricted to or much more abundant within the upstream and middle segments. Our analysis identified the middle section of the Volta Grande as critically important for the conservation of this diverse, endemic fish fauna. Additional research is urgently needed to determine dam operations that may optimize energy production with an environmental flow regime that conserves the river's unique habitat and biodiversity.

Large protected areas have been created in Brazilian Amazon intending to safeguard as much of its biodiversity as possible. Despite these intentions, such megareserves were created predominantly focusing on terrestrial organisms and ecosystems. Here, we assessed the ability of the current Brazilian Amazon protected areas network to efficiently safeguard its stream-dwelling fish fauna. Ecological niche models were built for 138 stream fish species using MaxEnt software. We performed a gap analysis and spatial prioritization under three different Amazon protected areas scenarios: (1) strictly protected areas (SPAs) only; (2) SPA plus sustainable use areas (SPA + SUA); and (3) SPA + SUA plus indigenous territories (SPA + SUA + IT). The species were classified according to their distribution range size and required representation targets. Widespread species usually had lower area under the curve (AUC) and true skill statistics (TSS) values, which would be expected for large and heterogeneous areas such as the Amazon. Only partial gap species were found, with 20% to 90% of required representation targets included in PAs, which was not enough for a complete protection. Most of the officially protected areas in the Brazilian Amazon do not correspond to areas with high direct conservation values for stream fishes, once the priority areas for these species conservation were outside the PAs, leaving a high portion of the regional vertebrate fauna inadequately protected. We conclude that fishes and other freshwater organisms and habitats should be explicitly included during systematic conservation planning in order to thoroughly protect the Brazilian Amazon biodiversity.

Dynamic flow regimes maintain critical connections between main channel and adjacent floodplain habitats that provide fish access to shelter, foraging, and spawning opportunities. Our study advances the understanding of these processes by exploring the importance of coupled longitudinal–lateral connectivity for determining species occurrence in headwater streams of the Amazon. Using a multispecies occupancy model, we revealed a clear pattern of species addition in the downstream direction in temporary floodplain ponds, associated with changes in the pool of potential colonists present in the channel and with increasing lateral hydrologic connectivity. Species that are more tolerant of stagnant waters and those able to disperse in shallow habitats (e.g., Anablepsoides micropus) occurred frequently in ponds along the entire longitudinal extent, whereas those species preferring lotic habitats were present only in the most downstream sites. We also observed increasing similarity of pond and channel communities with distance downstream. This study provides insights on the spatial structuring of tropical fish communities in response to flood-induced hydrologic connectivity and further highlights the vulnerability of floodplain fishes to modification in flooding regimes.

International audience; Agricultural land use is a primary driver of environmental impacts on streams. However, the causal processes that shape these impacts operate through multiple pathways and at several spatial scales. This complexity undermines the development of more effective management approaches, and illustrates the need for more in-depth studies to assess the mechanisms that determine changes in stream biodiversity. Here we present results of the most comprehensive multi-scale assessment of the biological condition of streams in the Amazon to date, examining functional responses of fish assemblages to land use. We sampled fish assemblages from two large human-modified regions, and characterized stream conditions by physical habitat attributes and key landscape-change variables, including density of road crossings (i.e. riverscape fragmentation), deforestation, and agricultural intensification. Fish species were functionally characterized using ecomorphological traits describing feeding, locomotion, and habitat preferences, and these traits were used to derive indices that quantitatively describe the functional structure of the assemblages. Using structural equation modeling, we disentangled multiple drivers operating at different spatial scales, identifying causal pathways that significantly affect stream condition and the structure of the fish assemblages. Deforestation at catchment and riparian network scales altered the channel morphology and the stream bottom structure, changing the functional identity of assemblages. Local deforestation reduced the functional evenness of assemblages (i.e. increased dominance of specific trait combinations) mediated by expansion of aquatic vegetation cover. Riverscape fragmentation reduced functional richness, evenness and divergence, suggesting a trend toward functional homogenization and a reduced range of ecological niches within assemblages following the loss of regional connectivity. These results underscore the often-unrecognized importance of different land use changes, each of which can have marked effects on stream biodiversity. We draw on the relationships observed herein to suggest priorities for the improved management of stream systems in the multiple-use landscapes that predominate in human-modified tropical forests.

The genus Colomesus is the sole representative of the family Tetraodontidae in the Amazon region. Here, Colomesus asellus was analyzed using conventional and molecular cytogenetic protocols. Its diploid chromosome number is 2n = 46 with 12 meta-, 10 submeta-, 16 subtelo-, and 8 acrocentric chromosomes and a fundamental number of FN = 84. An XX/XY sex chromosome system was identified. Mapping of 18S rDNA correlated with the nucleolus organizer regions (Ag-NORs) in the short arms of the 2 X chromosomes in females and in the Y chromosome in males. C-banding revealed heterochromatin in the centromeric regions of all chromosomes, except for pair 3. Prominent sex chromosome-specific heterochromatin amplification was observed, covering the short arms of the Y chromosome almost entirely. FISH with telomeric and tropomyosin (tpm1) sequences, respectively, revealed terminal signals in all chromosomes. The analysis of extended DNA fibers confirmed the colocalization and the interspersed pattern of the telomeric and tpm1 sequences. Thus, this study highlights the remarkable evolutionary dynamism presented by the Amazonian puffer fish regarding the differentiation of a heteromorphic XY sex chromosome system and a particular sex-specific amplification of rDNA sites. This is the first record of such an association in the Tetraodontidae family.

For species living in highly variable environments, the ability to perceive and respond to environmental cues by moving into favorable habitats should convey evolutionary advantages. Here we examined the spatial dynamics of an Amazonian pencil fish species that shows seasonally varying use of stream channel and temporary pool habitats. We hypothesized that movement into the pools should be driven by cues that reflect availability of spawning sites, whereas movement out of the pools should be driven by cues that help avoid entrapment as water level declines. Survival, detection, and movement probabilities were estimated from capture histories of individuals recorded on 13 surveys along a hydrological cycle. Differences between habitats were small for detection probability and survival. Movement from stream to pools was greatest during bankfull overflow, whereas movement from pools to stream was related to rapid decline in pool area. Entry to pools during overflow may allow fish to choose favorable spawning sites while still permitting a swift return to the stream if conditions in pools deteriorate. The ability to interpret hydrological cues seems to allow pencil fish to cope with environmental uncertainty by timing its use of seasonally available spawning sites while avoiding entrapment in desiccating pools.

Upstream range shifts of freshwater fishes have been documented in recent years due to ongoing climate change. River fragmentation by dams, presenting physical barriers, can limit the climatically induced spatial redistribution of fishes. Andean freshwater ecosystems in the Neotropical region are expected to be highly affected by these future disturbances. However, proper evaluations are still missing. Combining species distribution models and functional traits of Andean Amazon fishes, coupled with dam locations and climatic projections (2070s), we (a) evaluated the potential impacts of future climate on species ranges, (b) investigated the combined impact of river fragmentation and climate change and (c) tested the relationships between these impacts and species functional traits. Results show that climate change will induce range contraction for most of the Andean Amazon fish species, particularly those inhabiting highlands. Dams are not predicted to greatly limit future range shifts for most species (i.e., the Barrier effect). However, some of these barriers should prevent upstream shifts for a considerable number of species, reducing future potential diversity in some basins. River fragmentation is predicted to act jointly with climate change in promoting a considerable decrease in the probability of species to persist in the long-term because of splitting species ranges in smaller fragments (i.e., the Isolation effect). Benthic and fast-flowing water adapted species with hydrodynamic bodies are significantly associated with severe range contractions from climate change.

Is there only one electric eel species? For two and a half centuries since its description by Linnaeus, Electrophorus electricus has captivated humankind by its capacity to generate strong electric discharges. Despite the importance of Electrophorus in multiple fields of science, the possibility of additional species-level diversity in the genus, which could also reveal a hidden variety of substances and bioelectrogenic functions, has hitherto not been explored. Here, based on overwhelming patterns of genetic, morphological, and ecological data, we reject the hypothesis of a single species broadly distributed throughout Greater Amazonia. Our analyses readily identify three major lineages that diverged during the Miocene and Pliocene—two of which warrant recognition as new species. For one of the new species, we recorded a discharge of 860 V, well above 650 V previously cited for Electrophorus, making it the strongest living bioelectricity generator., A single species of electric eel, Electrophorus electricus, has been described. Here, de Santana et al. show that there are three major lineages of Electrophorus distributed across Greater Amazonia and describe two new species, one with a much stronger electric discharge than was previously known.

Com o propósito de identificar os impactos da variação climática na vida aquática da várzea da Amazônia Central, foi proposto um novo sítio do Programa de Pesquisa Ecológica de Longa Duração: Diversidade da Várzea (PELD-DIVA). Este trabalho apresenta a infraestrutura computacional e-DIVA, que constitui um processo de integração de diversas bases de dados ictiológicas referentes a diferentes sítios de pesquisa, além de oferecer uma arquitetura computacional para gestão e análise dos dados relacionados ao Programa.

A biodiversidade aquática e a elevada produtividade pesqueira da Bacia Amazônica se devem principalmente à dinâmica anual dos pulsos de inundação e às extensas áreas alagáveis. Alguns dos principais impactos da construção de barragens para geração de hidroeletricidade incidem precisamente nesta dinâmica hidrológica. A construção da Usina Hidrelétrica (UHE) Belo Monte interfere na dinâmica hidrológica da Volta Grande do Xingu (VGX) ao desviar a maior parte da vazão para fora desse trecho do rio. Com base em uma análise crítica da literatura sobre o impacto de barragens e de monitoramentos em campo, que vêm sendo conduzidos tanto pelo empreendedor quanto por pesquisas independentes, verificamos que seriam necessários volumes de água substancialmente maiores do que o hidrograma proposto pela empresa e pela Agência Nacional de Águas (ANA), para não causar a total ruptura na conexão do rio com as planícies alagáveis, com efeitos negativos em cascata que comprometem, inclusive, a segurança alimentar em toda a VGX. A proposta de testar o hidrograma estabelecido pela empresa por seis anos, com uma drástica redução de vazão e perda da previsibilidade e regularidade do pulso anual de inundação, fere o Princípio Precaucionário, contraria o conhecimento ecológico acumulado sobre o tema e coloca em risco o ambiente, a biota e os modos de vida das populações humanas estabelecidas naquela região.Palavras-chave: Volta Grande do Xingu. Juruna (Yudjá). Hidrograma de Consenso. Regras de operação. Belo Monte.

A new species of Paralithoxus is described from the Ajarani River, a small tributary of the Branco River basin, Roraima State, Brazilian Amazon. The genus Paralithoxus comprises species described from the Essequibo drainage in Guyana, Approuague and Maroni in French Guiana, Suriname River in Surinam, and more recently, from Jari and Amapá rivers, in Brazil. Despite occurring in a rock-bottomed fast-flowing stream as the other species of Paralithoxus, this is the first species of the genus collected at 900 m altitude, in the Serra da Mocidade highlands, an isolated and poorly accessible small mountain chain at the southern border of the Guiana Shield. The new species is distinguished from its congeners by having truncate teeth, color pattern with green spots on dark olive-brown background, alternating dark and light blotches on fins and by the pelvic fin being as long as or longer than the pectoral fin. Sex dimorphism of the species is described. Comments on morphology and osteology are provided and compared with congeners. RESUMO Uma nova espécie de Paralithoxus é descrita do rio Ajarani, um pequeno tributário da bacia do rio Branco, Estado de Roraima, Amazônia Brasileira. O gênero Paralithoxus é composto por espécies descritas para as drenagens do Essequibo na Guiana, Approuague e Maroni na Guiana Francesa, rio Suriname no Suriname, e mais recentemente, para os rios Jari e Amapá, no Brasil. Apesar de ocorrer em pequenos riachos com fundo rochoso e correnteza forte como o restante dos representantes de Paralithoxus, esta é a primeira espécie do gênero coletada a 900 m de altitude, na Serra da Mocidade, uma pequena cadeia de montanhas localizada em uma área isolada e de difícil acesso na porção sul do Escudo das Guianas. A nova espécie distingue-se de suas congêneres pela presença de dentes truncados, pelo padrão de coloração com manchas verde claras sobre fundo oliva-marrom escuro, alternando manchas claras e escuras nas nadadeiras e pelo comprimento relativo da nadadeira pélvica igual ou maior que o comprimento da nadadeira peitoral. O dimorfismo sexual da espécie é descrito. Comentários sobre a morfologia e osteologia da espécie são feitos e comparados com suas congêneres.

Brazil has a variety of aquatic ecosystems and rich freshwater biodiversity, but these components have been constantly damaged by the expansion of unsustainable activities. An array of different conservation strategies is needed, especially the creation of protected areas (PAs, hereafter). However, Brazil's PAs are biased towards terrestrial ecosystems and we argue that current PAs have limited efficacy in the protection of freshwater biodiversity. New PAs should better consider aquatic environments, covering entire basins, rivers and other freshwater habitats. We recommend ways to implement these PAs and provide guidance to avoid social impacts. Freshwater systems in Brazil provide essential goods and services but these ecosystems are being rapidly degraded and will be lost if not adequately protected. © 2018 The Authors. Diversity and Distributions Published by John Wiley & Sons Ltd

Hopliancistrus is an Ancistrini genus diagnosed by having few and very strong cheek odontodes on interopercular area, and a patch of strong and stiff odontodes on the antero-lateral border of the snout. The type species is herein redescribed based on types and recently collected specimens. In addition, four new congeneric species are described based on specimens collected in other parts of the Rio Xingu and Rio Tapajós basins. Hopliancistrus tricornis is distributed in the lower Rio Tapajós and is diagnosed by the possession of four branched anal-fin rays and relatively large white to yellow spots on trunk and pectoral and pelvic fins, and dark brown spots on dorsal, caudal and anal fins. Hopliancistrus munduruku is described based on specimens from Rio Jamanxim (Rio Tapajós basin) and Rio Curuá (Rio Xingu basin) and is diagnosed by the possession of five branched anal-fin rays and large yellow blotches on trunk and dark brown to black spots over the fins. Hopliancistrus wolverine is distributed in the rapids of the lower and middle Rio Xingu and is diagnosed by the possession of five branched anal-fin rays and conspicuous small yellow dots on head, trunk and fins. Hopliancistrus xikrin is distributed in medium- to small-sized tributaries of the lower portion of Rio Xingu basin, and is diagnosed by absence of contact between the transverse process of the first dorsal-fin pterygiophore and the transverse process of the second pterygiophore. Hopliancistrus xavante is distributed in the tributaries of upper Rio Xingu basin, and is diagnosed by having a thick skin covering the nuchal plate; by having large white spots on trunk and fins; and by the possession of five branched anal-fin rays. An osteological description and a key for species identification are also provided.

This study assessed the width of the trophic niche of four characid species (Bryconops giacopinii, Bryconops inpai, Hyphessobrycon aff. melazonatus and Iguanodectes geisleri) found under different co-occurrence circumstances in Amazonian upland streams. The study was conducted during the rainy season of 2011 at eight sites of two micro-basins of the Ducke Reserve, Manaus, Amazonas, Brazil. The four species were studied in the following circumstances: only one of the species occurring in the stream; two species co-occurring; three species co-occurring. The relative volume of the food items in the fish stomachs was used to calculate Hurlbert's trophic-niche breadth for the individuals of each species in the different co-occurrence circumstances. Hyphessobrycon aff. melazonatus changed their diet when occurring in syntopy with other characid species of similar feeding habits, as shown by a significant narrowing of its trophic niche. The opportunistic habits and great feeding flexibility of these characid species make the partitioning of food resources possible and act as an important ecological mechanism that facilitates the coexistence of different species, possibly by attenuating the effects of direct competition for food. In addition, the low carrying capacity of these upland forest streams may be an important environmental factor influencing the results of this study.

Current broad geographical distributions of species can only exist because individuals dispersed from their natal sites. The Amazon’s sailfin tetra Crenuchus spilurus has a geographical range of over 3 million km2, an area 5.7 times larger than France, which includes regions of very distinct abiotic and biotic conditions. What traits may aid in explaining such a broad geographical range, and which make the range exceptional? Here we investigate the species’ ecology and behavior using several approaches: direct field observations, ecological surveys, analyses of reproductive parameters, and diet. Broad trophic niche and frequent reproduction may help explain the wide geographical range, whereas most other traits are typical of short-ranged species: small body size, specific habitat requirements, small populations, low mobility, site-fidelity, low fecundity, and large relative size at maturation. We propose that the broad geographical range of C. spilurus is better explained by passive processes related to river dynamics. Interestingly, this species is one of few strongly dichromatic species of Amazon fish, having mutual signaling during courtship, and males exerting exclusive parental care of eggs and early larval stages. While the combination of such behavioral and ecological characteristics should promote differences among lineages and (eventually) speciation, populations far apart are remarkably morphologically similar. We suggest that ecology along with sexual selection may interplay and contribute to the inter-population morphological similarity, criterion on which Crenuchus is considered a monotypic genus.

Teleocichla preta nov. sp. inhabits the rapids along the Rio Xingu and lower portion of the Rio Iriri. It is the largest species in the genus, reaching 121·3 mm standard length (LS ) while others do not reach more than 87·8 mm LS . Teleocichla preta is distinguished from all other species of Teleocichla by the unique blackish (in live specimens) or dark brown (preserved specimens) overall colouration of the body, which masks the faint vertical bars or zig-zag pattern of blotches on the flanks. Teleocichla preta also has a deeper body and a deep laterally compressed caudal peduncle, unlike any other congener, as well as a stout lower pharyngeal tooth plate bearing molariform teeth on its median area.

Land use change and forest degradation have myriad effects on tropical ecosystems. Yet their consequences for low-order streams remain very poorly understood, including in the world´s largest freshwater basin, the Amazon. Determine the degree to which physical and chemical characteristics of the instream habitat of low-order Amazonian streams change in response to past local- and catchment-level anthropogenic disturbances. To do so, we collected field instream habitat (i.e., physical habitat and water quality) and landscape data from 99 stream sites in two eastern Brazilian Amazon regions. We used random forest regression trees to assess the relative importance of different predictor variables in determining changes in instream habitat response variables. Multiple drivers, operating at multiple spatial scales, were important in determining changes in the physical habitat and water quality of the sites. Although we found few similarities in modelled relationships between the two regions, we observed non-linear responses of specific instream characteristics to landscape change; for example 20 % of catchment deforestation resulted in consistently warmer streams. Our results highlight the importance of local riparian and catchment-scale forest cover in shaping instream physical environments, but also underscore the importance of other land use changes and activities, such as road crossings and upstream agriculture intensification. In contrast to the property-scale focus of the Brazilian Forest code, which governs environmental regulations on private land, our results reinforce the importance of catchment-wide management strategies to protect stream ecosystem integrity.

Climate change is poised to have fundamental impacts on the freshwater environments of the Amazon River Basin, and protected areas are routinely proposed as a possible management strategy to conserve freshwater fishes. However, there remains a paucity of information regarding the sensitivity of threatened fish species to climate‐induced changes in water quantity and quality. An expert‐based survey was used to address the following questions: (1) Are currently threatened fish species in Brazil also sensitive to projected effects of climate change? (2) Does the current conservation status of fish species also reflect their degree of sensitivity to climate change? and (3) What are the specific aspects of climate change that are likely to contribute the most to species sensitivity? Survey respondents evaluated 35 species (11 families) representing 50% of the threatened species in the Brazilian Amazon. The results suggest that the majority of threatened Brazilian fish species are considered highly sensitive to climate change impacts. Climate‐induced changes in water quality were, on average, considered a greater threat to species persistence than potential changes in water quantity. Survey results also suggest that fishes exhibit high sensitivity to changes in temperature and dissolved oxygen, and moderate to high sensitivity to changes in high‐flow (i.e. flood) and low‐flow (i.e. drought) regimes. A considerable mismatch was found between species conservation status and sensitivity to climate change, suggesting that perceptions of present‐day extinction risk do not necessarily provide insight into future risks associated with climate change. Species sensitivity to climate change showed no relationship to dispersal ability, indicating that protected areas may serve as important refugia for those species unable to keep pace with climate change. Despite this, the number and size of protected areas in Brazil have decreased over the past decade, largely to support the exploitation of hydropower and mining. Strategic conservation planning that involves existing and new protected areas for those species most at risk to climate change is warranted. Copyright © 2016 John Wiley & Sons, Ltd.

In an effort to ensure energy independence and exploit mineral resources, the governments of Amazonian countries are embarking on a major dam building drive on the basin’s rivers, with 191 dams finished and a further 246 planned or under construction. This rush to harvest the basin’s vast renewable energy capacity has come without proper consideration of the likely negative environmental externalities on the world’s most speciose freshwater and terrestrial biotas. Here we highlight the economic drivers for hydropower development and review the literature to summarise the impacts of dam building on Amazonian biodiversity. We identify both direct and indirect impacts through the anticipated loss, fragmentation and degradation of riparian habitats. We then propose a series of measures to assess, curb and mitigate the impacts of destructive dams on Amazonian biodiversity.

The temporal effect of discharge and limnology on fish composition and species diversity in a floodplain lake at the confluence of the Amazon and Negro Rivers was evaluated. Species richness, abundance and assemblage composition were strongly influenced by seasonal discharge of the Amazon and Negro Rivers, which affects lateral connectivity, water conductivity and temperature. As a consequence, temporal β-diversity was high in the lake and the assemblage was dominated by seasonally transient species. Relatively large species known to feed on resources within the floodplain were captured almost exclusively during the flood period. During the dry season, the assemblage was dominated by fishes adapted to harsh conditions of high temperature and low dissolved oxygen concentrations. An open system with high spatial and temporal heterogeneity created by the meeting of two large rivers with different water chemistry, Lago Catalao has a dynamic fish assemblage. Given its high temporal β-diversity and abundance of fishes, many of great importance in local fisheries, Lago Catalao and other floodplain lakes in this region merit special attention for conservation.

Studies of fish assemblages have demonstrated that the main channels of rivers contain ichthyofauna adapted to this environment. However, information regarding the effects of temporal and spatial variations on this ichthyofauna is scarce. Using data from benthic fish assemblages in a major tributary of the Amazon basin collected during two consecutive receding and two rising water seasons, we tested the hypothesis that there are marked variations in community composition between the receding and rising water seasons. An asymmetry in predictability was detected among samples from the receding and rising seasons. Predictability in terms of species composition was higher for receding than rising seasons. The continual disassembly and reassembly cycles (due to dispersal) of local communities across a spatially heterogeneous landscape could explain this difference. Depth and dissolved oxygen affected the distribution of some benthic fish species during the rising seasons. This study highlights the important contribution of marginal wetlands to the benthic ichthyofauna inhabiting the main channel of the Purus River, as well as other major Amazonian rivers.

Chalceus guaporensis is an endemic fish to the upper Madeira River whereas C. epakros is widespread in many rivers of the central and lower portions of the Amazon Basin, middle and upper Orinoco River Basin, the Essequibo River in Guyana and in the Nanay River in northern Peru. According to literature, both species do not occur in syntopy. We carried out ichthyological surveys along the Madeira River Basin and its rapids, and data on abundance, diet and habitat use were obtained for both species. Chalceus guaporensis and C. epakros are morphologically similar, occupying floodplain habitats and exploiting similar food resources. The former predominated upstream from the Jirau Fall, whereas the latter had most of its abundance bellow the last fall of the Madeira River; both species co-occurred along part of the rapids stretch and in the Machado River, but with strongly uneven abundances. This pattern may have developed in the past by speciation regarding the presence of the falls, while co-occurrence of the two species seems to be regulated by competitive interactions or maintained by slight differences in environmental requirements nowadays. The recent disruption of the Madeira River by two run-of-river dams built in cascade submerged a large portion of the rapids stretch and substituted it by semi-lenthic habitats created by the dam reservoirs, together with the construction of a fish passage. These environmental changes may allow the invasion of the upper reaches of the Madeira River by C. epakros, and disturb the population of endemic C. guaporensis. RESUMO Chalceus guaporensis é descrita como uma espécie endêmica do alto rio Madeira, enquanto C. epakros está amplamente distribuída em rios das porções central e inferior da bacia Amazônica, no médio e alto rio Orinoco, e nos rios Essequibo, na Guiana, e Nanay, no norte do Peru. A literatura não registra essas espécies como sintópicas. Expedições ictiológicas realizadas ao longo do rio Madeira e suas corredeiras nos deram a oportunidade de registrar a presença, abundância, habitat e dieta utilizadas por essas espécies. Chalceus guaporensis e C. epakros são muito similares morfologicamente, ocupam habitats inundáveis e apresentam espectro alimentar semelhante. A primeira espécie predominou a montante da cachoeira Jirau, enquanto que a segunda teve a maior parte de sua abundância registrada à jusante das cachoeiras do rio Madeira. Ambas espécies coocorreram ao longo de parte do trecho de corredeiras e no rio Machado, mas com abundâncias muito desiguais. Esse padrão pode ter se desenvolvido no passado, por especiação, em função da presença das corredeiras, enquanto a coocorrência das duas espécies parece ser regulada por interações competitivas ou mantida por diferenças sutis em requisitos ecológicos no tempo atual. O recente barramento do rio Madeira por duas hidrelétricas construídas em cascata submergiu uma grande porção do trecho de corredeiras e o substituiu por habitats semilênticos, criados pelos reservatórios das hidrelétricas a fio d’água, juntamente com a construção de uma passagem para peixes. Essas alterações ambientais podem permitir que C. epakros invada o trecho superior da bacia do rio Madeira, com possíveis impactos negativos sobre a população da espécie endêmica C. guaporensis.

Made available in DSpace on 2018-11-30T03:55:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-09-19 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Several hypotheses are used to explain species richness patterns. Some of them (e. g. species- area, species-energy, environment-energy, water-energy, terrestrial primary productivity, environmental spatial heterogeneity, and climatic heterogeneity) are known to explain species richness patterns of terrestrial organisms, especially when they are combined. For aquatic organisms, however, it is unclear if these hypotheses can be useful to explain for these purposes. Therefore, we used a selection model approach to assess the predictive capacity of such hypotheses, and to determine which of them (combined or not) would be the most appropriate to explain the fish species distribution in small Brazilian streams. We perform the Akaike's information criteria for models selections and the eigenvector analysis to control the special autocorrelation. The spatial structure was equal to 0.453, Moran's I, and require 11 spatial filters. All models were significant and had adjustments ranging from 0.370 to 0.416 with strong spatial component (ranging from 0.226 to 0.369) and low adjustments for environmental data (ranging from 0.001 to 0.119) We obtained two groups of hypothesis are able to explain the richness pattern (1) water-energy, temporal productivity-heterogeneity (AIC = 4498.800) and (2) water-energy, temporal productivity-heterogeneity and area (AIC = 4500.400). We conclude that the fish richness patterns in small Brazilian streams are better explained by a combination of Water-Energy + Productivity + Temporal Heterogeneity hypotheses and not by just one. Univ Fed Para UFPA, Lab Ictiol Altamira, Altamira, Para, Brazil Univ Estadual Maringa, Nucleo Pesquisas Limnol Ictiol & Aquicultura Nupe, Maringa, Parana, Brazil Univ Estadual Paulista UNESP, Lab Ictiol, Sao Jose Do Rio Preto, SP, Brazil Univ Paulista, Sorocaba, SP, Brazil Univ Estado Rio De Janeiro, Dept Ecol, Rio De Janeiro, RJ, Brazil Univ Fed Ceara, Dept Biol, Ctr Ciencias, Fortaleza, Ceara, Brazil Univ Fed Ceara, Inst Ciencias Mar LABOMAR, Fortaleza, Ceara, Brazil Univ Fed Rio Grande do Norte UFRN, Dept Bot Ecol & Zool, Ctr Biociencias, Natal, RN, Brazil Univ Fed Lavras UFLA, Dept Biol, Lavras, MG, Brazil UFT, Porto Nacl, Tocantins, Brazil Univ Fed Para UFPA, Inst Ciencias Biol, Belem, Para, Brazil INPA, Coordenacao Biodiversidade, Manaus, Amazonas, Brazil Univ Brasilia, Dept Zool, Brasilia, DF, Brazil Univ Fed Sao Carlos, Sorocaba, SP, Brazil Pontificia Univ Catolica Goias, Programa Mestrado Sociedade Tecnol & Meio Ambient, UNIEvangel, Goias Ctr Biol Aquat, Goiania, Go, Brazil UFES, Dept Ciencias Agr & Biol, Ctr Univ Norte Espirito Santo CEUNES, Sao Mateus, ES, Brazil Univ Estadual Paulista, Inst Biociencias, Botucatu, SP, Brazil Univ Fed Minas Gerais, Dept Genet Ecol & Evolucao, Inst Ciencias Biol, Belo Horizonte, MG, Brazil Univ Fed Goias, Dept Ecol, Inst Ciencias Biol, Campus 2 UFG, Goiania, Go, Brazil Univ Estadual Paulista UNESP, Lab Ictiol, Sao Jose Do Rio Preto, SP, Brazil Univ Estadual Paulista, Inst Biociencias, Botucatu, SP, Brazil CNPq: 457463/2012-0 CNPq: 552009/2011-3 CNPq: 471283/2006-1 CNPq: 304002/2014-3 FAPEMIG: 304002/2014-3

Context The replacement of native vegetation by exotic grasses for livestock production is driving landscape homogenization, habitat fragmentation and reducing connectivity between habitat patches in floodplains ecosystems. Objective In this context we examined how changes in native and exotic vegetation cover, connectivity and water depth affect the attributes of the small [standard length (SL)\80 mm as adults] and large-sized fish assemblages (SL C 80 mm as adults). Method We assessed the effects of water depth, exotic and native vegetation cover and habitat connectivityonthe abundance, species richness, body size andbiomassoffishassemblagesina25 km 2 areaofthe seasonal habitats of the Pantanal wetland over 5 years. Results We showed that fish assemblage response to meso-scale variation in water depth, vegetation cover and habitat connectivity in seasonal habitats is sizedependent. The gradient from exotic to natural vegetation cover did not affect the assemblages of small-sized fish,whichweremostlyregulatedbywaterdepth,habitat connectivity and the gradient from grassland to forest. However, besides being affected by water depth and habitat connectivity, large-sized fish were also affected by the gradient from exotic to natural vegetation cover. Conclusion Our results indicate that transformations in the landscape and changes in the dynamics of inundation may have negative consequences for the long-term persistence of fish assemblages in the Pantanal wetlands.

Monthly (April 2009 to May 2010) bottom-trawl sampling for Brachyplatystoma species along the rapids stretch of the Madeira River in Brazil revealed that Brachyplatystoma rousseauxii larvae and juveniles were present in low abundances in all areas and during all hydrological periods. The presence of larvae and juveniles throughout the hydrological cycle suggests asynchronous spawning in the headwaters of the Madeira River.

The genus Colomesus is the sole representative of the family Tetraodontidae in the Amazon region. Here, Colomesus asellus was analyzed using conventional and molecular cytogenetic protocols. Its diploid chromosome number is 2n = 46 with 12 meta-, 10 submeta-, 16 subtelo-, and 8 acrocentric chromosomes and a fundamental number of FN = 84. An XX/XY sex chromosome system was identified. Mapping of 18S rDNA correlated with the nucleolus organizer regions (Ag-NORs) in the short arms of the 2 X chromosomes in females and in the Y chromosome in males. C-banding revealed heterochromatin in the centromeric regions of all chromosomes, except for pair 3. Prominent sex chromosome-specific heterochromatin amplification was observed, covering the short arms of the Y chromosome almost entirely. FISH with telomeric and tropomyosin (tpm1) sequences, respectively, revealed terminal signals in all chromosomes. The analysis of extended DNA fibers confirmed the colocalization and the interspersed pattern of the telomeric and tpm1 sequences. Thus, this study highlights the remarkable evolutionary dynamism presented by the Amazonian puffer fish regarding the differentiation of a heteromorphic XY sex chromosome system and a particular sex-specific amplification of rDNA sites. This is the first record of such an association in the Tetraodontidae family.

© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. More than a hundred hydropower dams have already been built in the Amazon basin and numerous proposals for further dam constructions are under consideration. The accumulated negative environmental effects of existing dams and proposed dams, if constructed, will trigger massive hydrophysical and biotic disturbances that will affect the Amazon basin's floodplains, estuary and sediment plume. We introduce a Dam Environmental Vulnerability Index to quantify the current and potential impacts of dams in the basin. The scale of foreseeable environmental degradation indicates the need for collective action among nations and states to avoid cumulative, far-reaching impacts. We suggest institutional innovations to assess and avoid the likely impoverishment of Amazon rivers.

Combined effects of climate change and deforestation have altered precipitation patterns in the Amazon. This has led to changes in the frequency of extreme events of flood and drought in recent decades and in the magnitude of the annual flood pulse, a phenomenon that influences virtually all aspects of river-floodplain ecosystem dynamics. Analysis of long-term data revealed abrupt and synchronous changes in hydrology and fish assemblage structure of a floodplain lake near the confluence of Amazon and Negro rivers. After an intense drought in 2005, the assemblage assumed a different and fairly persistent taxonomic composition and functional structure. Declines in abundance after 2005 were more pronounced for species of all sizes having equilibrium life history strategy, large species with periodic life history strategy, and for all trophic levels except primary consumers. Our results suggest that the extreme drought triggered changes in the fish assemblage and subsequent anomalous hydrological conditions have hampered assemblage recovery. These findings stress the need to account for climatic-driven hydrological changes in conservation efforts addressing aquatic biodiversity and fishery resources in the central Amazon.

This study assessed the diet of two poorly known syntopic fish species of the family Crenuchidae, Characidium aff. declivirostre and Leptocharacidium omospilus, in a Presidente Figueiredo´ rocky stream, Amazonas, Brazil. The stomach contents were analyzed and their Frequency of Occurrence (FO %) and Relative Volume (Vol %) were combined in a Feeding Index (IAi). We examined 20 individuals of C. aff. declivirostre and 23 of L. omospilus. The Morisita-Horn Index was used to estimate the overlap between the diets of these species. Immature insects were the most valuable items consumed by both fish species. The diet of C. aff. declivirostre was mainly composed of larvae and pupae of Chironomidae, while L. omospilus predominantly consumed larvae of Hydroptilidae, Hydropyschidae and Pyralidae. Thus, both species were classified as autochthonous insectivorous. Characidium aff. declivirostre was considered a more specialized species, probably reflecting lower feeding plasticity or the use of more restricted microhabitats compared to L. omospilus. When the food items were analyzed at the family taxonomic level, the diet overlap between these species was considered moderate (Morisita-Horn Index = 0.4). However, a more thorough analysis, at the genus level, indicates a very low diet overlap. Therefore, we conclude that the feeding segregation between C. aff. declivirostre and L. omospilus may favor their co-existence, despite their high phylogenetic closeness. Resumo O presente estudo investigou a dieta de duas espécies de peixes pouco conhecidas da família Crenuchidae, Characidium aff. declivirostre e Leptocharacidium omospilus, sintópicas de um riacho de corredeira do município de Presidente Figueiredo, Estado do Amazonas, Brasil. O conteúdo estomacal de cada exemplar foi analisado pelos métodos de Frequência de Ocorrência (FO%) e Volume Relativo (Vol%) e, posteriormente, combinados para o cálculo do Índice Alimentar (IAi). Foram analisados 20 indivíduos de C. aff. declivirostre e 23 de L. omospilus. A sobreposição entre a dieta das duas espécies foi estimada pelo Índice Simplificado de Morisita-Horn. Insetos imaturos foram os principais itens consumidos por ambas as espécies. A dieta de C. aff. declivirostre mostrou preferência acentuada por larvas e pupas de Chironomidae, enquanto que a dieta de L. omospilus concentrou-se em larvas de Hydroptilidae, de Hydropyschidae e de Pyralidae. Portanto, as espécies foram classificadas troficamente como insetívoras consumidoras de itens autóctones. A dieta de C. aff. declivirostre foi mais especializada, o que pode ser reflexo de uma menor plasticidade alimentar ou do uso de microhabitats mais restritos, quando comparado a L. omospilus. Ao analisar os itens alimentares em nível taxonômico de família, a sobreposição alimentar foi considerada moderada (Índice de Morisita-Horn = 0,4). Entretanto, análises mais refinadas, em nível de gênero, indicaram sobreposição muito baixa na dieta. Conclui-se que tal segregação alimentar pode favorecer a coexistência de C. aff. declivirostre e L. omospilus, mesmo que sejam espécies filogeneticamente próximas.

Multimetric indices (MMIs) are widely used for assessing ecosystem condition and they have been developed for a variety of biological assemblages. However, when multiple assemblages are assessed at sites, the assessment results may differ because of differing physiological sensitivities to particular stressor gradients, different organism size and guilds, and the effects of different scales of disturbances on the assemblages. Those differences create problems for managers seeking to avoid type-1 and type-2 statistical errors. To alleviate those problems, we used an anthropogenic disturbance index for selecting and weighting metrics, modeled metrics against natural variability to reduce the natural variability in metrics, and developed an MMI based on both fish and aquatic insect metrics. We evaluated eight different ways of calibrating and combining candidate metrics and found that MMIs with unweighted and modeled aquatic insect and fish metrics were the preferred MMI options.

Bunocephalus is the most species-rich Aspredinidae genus, corresponding to a monophyletic clade with 13 valid species. However, many species have their classification put in question. Here, we analyzed individuals from four Amazonian populations of Bunocephalus coracoideus by cytogenetic and molecular procedures. The geographic distribution, genetic distances and karyotype data indicate that each population represents an Evolutionary Significant Unit (ESU). Cytogenetic markers showed distinct 2n and karyotype formulas, as well as different numbers and locations of the rDNA sites among ESUs. One of such populations (ESU-D) highlighted an extensive polymorphic condition, with several cytotypes probably due to chromosomal rearrangements and meiotic non-disjunctions. This resulted in several aneuploid karyotypes, which was also supported by the mapping of telomeric sequences. Phylograms based on Maximum Likelihood (ML) and Neighbor Joining (NJ) analyses grouped each ESU on particular highly supported clades, with the estimation of evolutionary divergence indicating values being higher than 3.8-12.3% among them. Our study reveals a huge degree of chromosomal and genetic diversity in B. coracoideus and highly points to the existence of four ESUs in allopatric and sympatric speciation processes. In fact, the high divergences found among the ESUs allowed us to delimitate lineages with taxonomic uncertainties in this nominal species. © 2017 Ferreira, Garcia, Matoso, de Jesus, Cioffi, Bertollo, Zuanon and Feldberg.

SUMMARY 1. The geographical ranges of species are influenced by three components: spatial distribution ofenvironmental conditions, biotic interactions and the dispersal capacity of species. The scarcity of dis-tributional records in vast regions such as the Amazon impedes understanding of fish distribution.Predictive distribution models have emerged as a better alternative to surpass this problem, but theabsence of large-scale maps for aquatic variables has been suggested as an important limitation.2. We aimed to evaluate the use of macroclimatic variables as surrogates for local limnological vari-ables in the Brazilian Amazon. Ordinary least squares model were used to predict the local habitatvariables from climatic and geomorphological information as macroscale variables. Models for sixstream-dwelling fish were built in MaxEnt and validated using area under curve and true skill statis-tics (TSS).3. All local variables were predicted successfully (R 2 > 0.39), and MaxEnt models had good suitabil-ity using the macroscale variables (TSS higher than 0.70). We conclude that macroscale variables canbe effective surrogates for local habitat variables, at least for large-scale analyses on poorly sampledregions such as the Brazilian Amazon.Keywords: Amazon, aquatic variables, macroscale variables, modelling species distribution, stream fish

The cichlid Mesonauta festivus is common and abundant among macrophyte stands along a large geographical range of the Amazonas and Parana-Paraguay basins, in South America. This broad geographical range highlights the species’ dispersion ability, which can be attributed to specific biological and behavioral traits. However, the dispersion ability does not account for the broad geographical range alone, as the species must be able to establish populations in a range of environments, which include marginal areas of large rivers with different water types, floodplain lakes, and small terra-firme streams. In this work we investigated the specie’s ecology, biological traits and behavior in order to understand what and how its traits may have allowed it to attain such broad geographical range and aid in establishing local populations. Regarding its dispersion ability we stress the capability of swimming in the pelagic region, which is remarkable for this species and uncommon among Neotropical cichlids. Its vagility is high even when juveniles are under parental care. Regarding population establishment, the high environmental tolerance stands out, allowing the species to live under strikingly different abiotic conditions. In addition, the small size of first sexual maturation and its capability of spawning along the whole hydrologic cycle (apparently not associated to a specific environmental cue) may also facilitate the establishment of populations into new environments. Moreover, the behavior of mimicking dead leaves, which is mainly performed by juveniles, may lessen predation pressures. Under an eco-evolutionary perspective, the traits highlighted in this work may buffer selective pressures experienced by populations in different biotic and/or abiotic conditions, which may also favor the increasing of the geographical range by allowing the evolutionary lineage to remain similar even in disconnected and/or striking different environments.