Fishes from Yarinacocha lake: an emblematic Amazonian ecosystem in the lower Ucayali River basin, Pucallpa, Peru / Peixes do lago Yarinacocha: um ecossistema amazônico emblemático na bacia do baixo rio Ucayali, Pucallpa, Peru

The Yarinacocha lake is an emblematic ecosystem of the Peruvian Amazon, representing the main point of fish landing and a tourist attraction in the city of Pucallpa. The wide fauna diversity in this area has made it the target of various studies, although for fish species most of them were focused on commercial species. In this work, we carried out the first ichthyofauna species inventory of the Yarinacocha lake, sampling throughout the entire lake during the rainy and dry seasons and considering also all previously recorded species deposited in the Ichthyological Collection of the MUSM with the same locality. A total of 164 fish species were recorded, representing 10 orders (plus Eupercaria), 34 families and 116 genera. Characiformes was the order with more species (68 spp., 41.5%) followed by Siluriformes (59 spp., 36%), Cichliformes (17 spp., 10.5%), and Gymnotiformes (8 spp., 4.9%). The most highly represented families, including almost 55.5% of the total diversity obtained, were Characidae (23 spp., 14%), followed by Cichlidae (17 spp., 10.4%), Loricariidae (14 spp., 8.5%), Pimelodidae (13 spp., 7.9%), Doradidae (13 spp., 7.4%) and Anostomidae (12 spp., 7.3%). From the total fish species recorded in this study, only 22 are considered protected species following the IUCN criteria and 109 species have commercial importance, including 90 ornamental species (54.8%). Our results contribute to the knowledge of the ichthyofauna of the Yarinacocha lake and can be used as a starting point for its conservation and sustainable management over time.

O lago Yarinacocha é um ecossistema emblemático da Amazônia peruana, representando o principal ponto de desembarque de peixes e também uma atração turística da cidade de Pucallpa. A grande diversidade faunística nesta área a tornou alvo de vários estudos, embora para as espécies de peixes a maioria deles tenha sido focada em espécies comerciais. Neste trabalho, realizamos o primeiro inventário da ictiofauna do lago Yarinacocha, amostrando todo o lago durante as estações chuvosa e seca, e também considerando todas as espécies depositadas na Coleção Ictiológica do MUSM dessa localidade. Um total de 164 espécies de peixes foram registradas, representando 10 ordens (mais Eupercaria), 34 famílias e 116 gêneros. Characiformes foi a ordem com mais espécies (68 espécies, 41,5%), seguida por Siluriformes (59 espécies, 36%), Cichliformes (17 espécies, 10,5%) e Gymnotiformes (8 espécies, 4,9%). As famílias mais representadas, incluindo quase 55,5% da diversidade total obtida, foram Characidae (23 spp., 14%), seguido por Cichlidae (17 spp., 10,4%), Loricariidae (14 spp., 8,5%), Pimelodidae (13 spp., 7,9%), Doradidae (13 spp., 7,4%) e Anostomidae (12 spp., 7,3%). Do total de espécies de peixes registradas neste estudo, apenas 22 são consideradas espécies protegidas seguindo os critérios da IUCN e 109 espécies têm importância comercial, incluindo 90 espécies ornamentais (54,8%). Nossos resultados contribuem para o conhecimento da ictiofauna do lago Yarinacocha e podem ser utilizados como ponto de partida para sua conservação e manejo sustentável ao longo do tempo.

Lista de especies de peces de la cuenca del río Ucayali, Perú

En este trabajo se presenta una lista actualizada de los registros de especies de peces de la cuenca del río Ucayali, Perú, provenientes de datos publicados y no publicados. Los resultados muestran que la cuenca del Ucayali presenta una ictiofauna rica y diversificada con el registro de 734 especies distribuidas en 15 órdenes, 49 familias y 292 géneros. La Ictiofauna está compuesta por peces miniatura (4%), peces pequeños (39%), medianos (41%), grandes (13%) y gigantes (3%). Los grupos dominantes son los Characiformes (312 especies, 43.0 %), Siluriformes (270 especies, 36.8%), Gymnotiformes (51 especies, 6.9%), y Cichliformes (50 especies, 6.8%). Parte de la ictiofauna es compartida con cuencas adyacentes como Marañón, y Amazonas peruano, principalmente en la región de confluencia, lo que contribuye a la notable diversidad de peces en la cuenca. Se observó una alta riqueza de especies con distribución restricta de los géneros Orestias, Astroblepus, Trichomycterus, Hemibrycon, entre otras especies, que ocurren en la región de cabeceras. Estimativos de riqueza de especies considerando su distribución por cada 100 m de altitud, indican que la cuenca del Ucayali esta subestimada, esperándose encontrar hasta 1125 especies. Los resultados aquí presentados son antecedentes que coadyuvaran a la toma de decisiones con fines de conservación y desarrollo sustentable en la región amazónica.

This study presents an updated checklists of the fish species recorded in the Ucayali River basin, Peru, from published and unpublished data. Ucayali River basin shows a rich and diversified ichthyofauna, with 734 species distributed in 15 orders, 49 families and 292 genera. It is composed by miniature fishes (4 %, < 2.6 cm of standard length), small fishes (39 %), medium fishes (41 %), large fishes (13 %) and giants (3 %). The dominant groups are Characiformes (312 species, 43.0 %), Siluriformes (270 species, 36.8 %), Gymnotiformes (51 species, 6.9 %) and Cichliformes (50 species, 6.8 %). Part of the ichthyofauna is shared with the adjacent basins as Marañón and Amazon, mainly in the confluence area, which contribute to the highest diversity of fishes in the Ucayali basin. High diversity of fishes with restricted distribution was observed, among them Orestias, Astroblepus, Trichomycterus, Hemibrycon genera that occur in the headwaters. Estimates of species richness considering their distribution per 100 m of altitude, show that the Ucayali basin is underestimated, expecting to find up to 1125 species. The results presented here are background information that will contribute to decision-making for conservation and sustainable development purposes in the Amazon region.

Peces de la cuenca del río Chira, Piura, Perú / Peces de la cuenca del río Chira, Piura, Perú

Abstract Chira River is located on the north coast of Peru. The scant information of the ichthyofauna from coastal drainages from Peru is noteworthy. The aim of this study is to characterize the ichthyofauna along the Chira River basin in terms of diversity and altitudinal range distribution. The material examined belongs to the Ichthyological collection of the Natural History Museum (MUSM). The diversity of fishes is composed of 27 species belonging to 19 families and ten orders. Siluriformes and Characiformes were the most diverse, consisting of 22% (six species) for each one. Five species are new records for the Chira River (three natives and two non-natives). Six marine species and seven exotic species were recorded as well. The altitudinal distribution patterns for all species were registered. This study increases the known diversity of freshwater fishes from Pacific Drainage Rivers in Peru, and it could be used for management and conservation plans.

Resumen El río Chira está ubicado en la costa norte del Perú. La escasa información de la ictiofauna de las cuencas costeras del Perú es notable. El objetivo de este estudio es caracterizar la ictiofauna en la cuenca del río Chira en términos de diversidad y rango de distribución altitudinal. El material examinado pertenece a la colección ictiológica del Museo de Historia Natural (MUSM). La diversidad de peces está compuesta por 27 especies pertenecientes a 19 familias y 10 órdenes. Cinco especies son nuevos registros para el río Chira (tres nativas y dos no nativas). Fueron registradas seis especies marinas y siete especies exóticas. Este estudio incrementa el conocimiento de la diversidad de peces de las cuencas costeras en Perú, y puede ser usado para planes de manejo y conservación.

Unveiling biogeographical patterns of the ichthyofauna in the Tuichi basin, a biodiversity hotspot in the Bolivian Amazon, using environmental DNA.

To date, more than 2400 valid fish species have been recorded in the Amazon basin. However, some regions remain poorly documented. This is the case in the Beni basin and in particular in one of its main sub-basins, the Tuichi, an Andean foothills rivers flowing through the Madidi National Park in the Bolivian Amazonia. The knowledge of its ichthyological diversity is, however, essential for the management and protection of aquatic ecosystems, which are threatened by the development of infrastructures (dams, factories and cities), mining and deforestation. Environmental DNA (eDNA) has been relatively little used so far in the Amazon basin. We sampled eDNA from water in 34 sites in lakes and rivers in the Beni basin including 22 sites in the Tuichi sub-basin, during the dry season. To assess the biogeographical patterns of the amazonian ichthyofauna, we implemented a metabarcoding approach using two pairs of specific primers designed and developed in our laboratory to amplify two partially overlapping CO1 fragments, one of 185bp and another of 285bp. We detected 252 fish taxa (207 at species level) among which 57 are newly identified for the Beni watershed. Species compositions are significantly different between lakes and rivers but also between rivers according to their hydrographic rank and altitude. Furthermore, the diversity patterns are related to the different hydro-ecoregions through which the Tuichi flows. The eDNA approach makes it possible to identify and complete the inventory of the ichthyofauna in this still poorly documented Amazon basin. However, taxonomic identification remains constrained by the lack of reference barcodes in public databases and does not allow the assignment of all OTUs. Our results can be taken into account in conservation and management strategies and could serve as a baseline for future studies, including on other Andean tributaries.

Age validation and contrasted growth performances of Pseudoplatystoma punctifer (Siluriformes: Pimelodidae) in two river systems of the Western Amazon

The doncella Pseudoplatystoma punctifer is an economically and ecologically important catfish in the Amazon basin. However, little is known about its age, growth and population dynamics parameters. This study aims to validate the formation of growth marks in vertebrae of individuals collected from two rivers systems of the Peruvian Amazon (Amazon-Marañón-Ucayali and Putumayo) and compare growth parameters using the von Bertalanffy growth function between sexes and systems. A total of 372 individuals from the Amazon-Marañón-Ucayali (AMU) system and 93 from the Putumayo River were analyzed. The formation of one growth ring per year was validated and the individual ages ranged from zero to nine years old. Females grew significantly larger than males in both systems. Both females and males grew significantly better in the AMU system than in the Putumayo River. Maximum observed length and size at maturity in the AMU system were lower than those reported in previous studies in the area, and together with an important proportion of juveniles in the catches, suggest that the species is heavily exploited. Further studies on the reproductive biology and population dynamics of the doncella are needed in order to implement management measures more in line with the current situation.(AU)

La doncella Pseudoplatystoma punctifer es un bagre de importancia económica y ecológica en la cuenca Amazonica. Pese a ello, poco se conoce acerca de parámetros de edad, crecimiento y dinámica poblacional. Este estudio tuvo como objetivo validar la formación de marcas de crecimiento en vértebras de individuos colectados en dos sistemas fluviales de la Amazonia Peruana (Amazonas-Marañón-Ucayali y Putumayo) y comparar los parámetros de crecimiento usando la función de von Bertalanffy entre sexos y sistemas. Fueron analizados 372 individuos del sistema Amazonas-Marañón-Ucayali (AMU) y 93 del Putumayo. Se validó la formación de un anillo de crecimiento por año, la edad osciló entre cero y nueve años. Las hembras fueron significativamente más grandes que los machos en ambos sistemas. Para ambos sexos el crecimiento fue significativamente mayor en el sistema AMU que en el Putumayo. Las máximas tallas y edades de primera madurez observadas en el sistema AMU fueron menores a las reportadas en estudios previos en el área, y junto con un considerable porcentaje de juveniles presentes en las capturas, se sugiere que la especie está siendo fuertemente explotada. Son necesarios estudios de biología reproductiva y dinámica poblacional de doncella para implementar medidas de manejo acordes a la situación actual.(AU)

Diversidad ictiológica de la quebrada Mayapo, Amazonia Peruana / Ichthyological diversity of the Mayapo stream, Peruvian Amazon

Resumen El presente estudio reporta la diversidad ictiológica de la quebrada Mayapo en base a material depositado en la Colección Ictiológica del Museo de Historia Natural de la Universidad Nacional Mayor de San Marcos (MUSM), en los años 2005, 2009 y 2010, proveniente de 30 puntos de muestreo de la quebrada Mayapo y afluentes ubicados entre los 256 y 557 m de altitud. Se identificaron 60 especies agrupadas en 39 géneros, 16 familias y cuatro órdenes, siendo los órdenes Characiformes y Siluriformes y las familias Characidae y Loricariidae los grupos más representativos. La diversidad de especies fue moderada, en comparación a otras evaluaciones en la Amazonia peruana. La composición taxonómica siguió el patrón predominante en aguas continentales de la Región Neotropical y en la Amazonia peruana. Se registraron especies de importancia pesquera, hábitos migratorios y distribución restringida.

Abstract The ichthyological diversity of the Mayapo stream is described based on material from the Ichthyological Collection of the Natural History Museum of the Universidad Nacional Mayor de San Marcos (UNMSM). We analysed material from 30 sample points of the Mayapo stream and tributaries, collected in 2005, 2009, and 2012. The points were located between 256 and 557 m of altitude. A total of 60 species grouped in 39 genera, 16 families, and four orders were identified. The Characiformes and Siluriformes orders including the Characidae and Loricariidae families were the most representative groups. We concluded that total ichthyological diversity in Mayapo stream and tributaries was moderated compared with previous studies in the Peruvian Amazon. Additionally, the taxonomic composition showed the common diversity pattern found in the Neotropical freshwaters and Peruvian Amazon. Finally, we also remark on fisheries species, migratory behaviours, and restricted distribution.

A new species of Mastiglanis Bockmann 1994 (Siluriformes: Heptapteridae) from the Amazon River basin, Peru.

Mastiglanis is a genus of heptapterid catfish represented by two valid species. These freshwater species are widely distributed along the Amazon, Orinoco, and Maroni River basins. However, a taxonomic review of specimens collected in the Putumayo and Nanay rivers, Amazon River basin in Peru revealed a new species of Mastiglanis. A morphological analysis was completed for morphometric (36 measurements) and meristic (20 counts) data. Osteological counts and descriptions were made from clear and stained specimens and x-rays images. The new species of Mastiglanis differs from M. asopos and M. durantoni by having a long pelvic fin, short snout, eight branched anal-fin rays, and a higher number of vertebrae and gill rakers. The distribution of the new species is restricted to the upper Amazon River basin.

The combined effects of climate change and river fragmentation on the distribution of Andean Amazon fishes.

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.

A database of freshwater fish species of the Amazon Basin.

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.

Freshwater fish diversity hotspots for conservation priorities in the Amazon Basin.

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.

Using community phylogenetics to assess phylogenetic structure in the Fitzcarrald region of Western Amazonia

Here we explore the use of community phylogenetics as a tool to document patterns of biodiversity in the Fitzcarrald region, a remote area in Southwestern Amazonia. For these analyses, we subdivide the region into basin-wide assemblages encompassing the headwaters of four Amazonian tributaries (Urubamba, Yuruá, Purús and Las Piedras basins), and habitat types: river channels, terra firme (non-floodplain) streams, and floodplain lakes. We present a robust, well-documented collection of fishes from the region including 272 species collected from 132 field sites over 63 field days and four years, comprising the most extensive collection of fishes from this region to date. We conduct a preliminary community phylogenetic analysis based on this collection and recover results largely statistically indistinguishable from the random expectation, with only a few instances of phylogenetic structure. Based on these results, and of those published in other recent biogeographic studies, we conclude that the Fitzcarrald fish species pool accumulated over a period of several million years, plausibly as a result of dispersal from the larger species pool of Greater Amazonia.(AU)

Aquí exploramos el uso de la filogenética de comunidades como herramienta para documentar patrones de biodiversidad en la región de Fitzcarrald, un área remota en el suroeste de la Amazonía. Para estos análisis subdividimos la región en grupos de toda la cuenca que abarcan las cabeceras de cuatro tributarios del Amazonas (cuencas Urubamba, Yuruá, Purús y Las Piedras) y en los tipos de hábitat: canales fluviales, arroyos de tierra firme (sin planicie aluvial) y lagos de planicie aluvial. Presentamos una colección de peces robusta y bien documentada que incluye 272 especies, colectadas a lo largo de cuatro años y 63 días de campo, en 132 puntos de monitoreo. Convirtiéndose en la colección más extensa de peces de esta región hasta la fecha. Realizamos un análisis filogenético preliminar de la comunidad basado en esta recopilación y recuperamos resultados en gran medida estadísticamente indistinguibles de la expectativa aleatoria, con sólo unos pocos casos de estructura filogenética. Basándonos en estos resultados y los publicados en otros estudios biogeográficos recientes, concluimos que el grupo de especies de peces de Fitzcarrald acumulado durante un período de varios millones de años, se debe posiblemente al resultado de la dispersión del mayor grupo de especies de la Gran Amazonia.(AU)

Redescription of Ancistrus greeni (Siluriformes: Loricariidae), and description of a new species from the río Madre de Dios basin, Peru

A new species of Ancistrus is described from minor tributaries of the río Madre de Dios basin (Cusco - Madre de Dios - Puno), in Peru. The new species shares with A. greeni an uncommon unicusp dentition; but it is distinguished from A. greeni by a larger orbital diameter, deeper caudal peduncle, and larger adipose-fin spine. The redescription of A. greeni is provided, and its recognition along with the discovery of this new species increases to five the officially number of Ancistrus species from the río Madre de Dios basin. The lectotype and paralectotype of A. greeni are provided.(AU)

Uma nova espécie de Ancistrus é descrita de pequenos tributários da bacia do rio Madre de Dios (Cusco - Madre de Dios - Puno), no Peru. A nova espécie compartilha com A. greeni uma dentição unicuspidada pouco comum e é diagnosticada de A. greeni pelo maior diâmetro orbital, maior altura do pedúnculo caudal e maior espinho da nadadeira adiposa. A redescrição de A. greeni é fornecida, e seu reconhecimento juntamente com a descoberta dessa nova espécie incrementam para cinco o número oficial de Ancistrus registradas para a bacia do rio Madre de Dios. O lectótipo e paralectótipo de A. greeni são fornecidos.(AU)

Revisión taxonómica de la rana marsupial Gastrotheca peruana (Amphibia: Hemiphractidae) en base al gen mitocondrial 16S / Taxonomic evaluation of the marsupial frog Gastrotheca peruana (Amphibia: Hemiphractidae) based on mitochondrial 16S rRNA gene

Se revisa el estado taxonómico de Gastrotheca peruana usando métodos filogenéticos en base a secuencias de 16S rRNA. Los árboles de máxima verosimilitud y Bayesiano mostraron que las variantes génicas de G. peruana forman dos clados que no son hermanos. Uno de estos clados se distribuye en el norte de Perú, incluyendo un individuo procedente de la localidad típica de G. peruana dissimilis. El segundo clado está restringido al centro de Perú y contiene individuos de las localidades tipo de dos formas nominales, G. p. peruana y G. p. junensis, y es hermano de G. aratia. De esta forma, reconocemos dos especies dentro de lo que actualmente se conoce como G. peruana. Restringimos Gastrotheca peruana a las poblaciones del centro de Perú (departamentos de Ancash, Lima, Pasco y Junín) y asignamos Gastrotheca dissimilis a las poblaciones de los departamentos de La Libertad y Cajamarca.

The taxonomic status of Gastrotheca peruana is evaluated using phylogenetic methods and 16S gene sequences. The maximum likelihood and Bayesian trees showed that the genetic variants of G. peruana form two clades that are not sister to each other. One of these clades is present in northern Perú and includes a specimen collected at the type locality of G. peruana dissimilis. The other clade is restricted to central Peru and contains individuals from type localities of two nominal forms, G. p. peruana and G. p. junensis, and is sister to G. aratia. Our results suggest that G. peruana sensu lato currently encompass two species. We restrict Gastrotheca peruana to populations from central Perú (departments of Ancash, Lima, Pasco and Junín) and assign populations from departments of La Libertad and Cajamarca to Gastrotheca dissimilis.

Unexpected fish diversity gradients in the Amazon basin.

Using the most comprehensive fish occurrence database, we evaluated the importance of ecological and historical drivers in diversity patterns of subdrainage basins across the Amazon system. Linear models reveal the influence of climatic conditions, habitat size and sub-basin isolation on species diversity. Unexpectedly, the species richness model also highlighted a negative upriver-downriver gradient, contrary to predictions of increasing richness at more downriver locations along fluvial gradients. This reverse gradient may be linked to the history of the Amazon drainage network, which, after isolation as western and eastern basins throughout the Miocene, only began flowing eastward 1-9 million years (Ma) ago. Our results suggest that the main center of fish diversity was located westward, with fish dispersal progressing eastward after the basins were united and the Amazon River assumed its modern course toward the Atlantic. This dispersal process seems not yet achieved, suggesting a recent formation of the current Amazon system.

Revision of Gymnotus (Gymnotiformes: Gymnotidae) from the Upper Madeira Basin of Bolivia and Peru, with descriptions of two new species.

Banded Knifefishes (Gymnotus, Gymnotidae) comprise the most species-rich genus of Neotropical electric fishes, with 41 species currently described from throughout the humid Neotropics, from Mexico to Argentina. Despite substantial alpha-taxonomic work in recent years, the diversity of Gymnotus in some regions remains poorly understood. Here we describe the Gymnotus fauna of the Upper Madeira basin of Bolivia and Peru from examination of more than 240 adult specimens. Species are delimited and described using body proportions (traditional morphometrics), fin-ray, squamation and laterosensory-pore counts (meristics), quantitative shape differences (geometric morphometrics), osteological traits, and color patterns. Comparisons of standardized linear measures as well as multivariate statistical methods validate the presence in the Upper Madeira basin of three previously described species, two with wide-spread geographic distributions throughout Greater Amazonia (G. carapo and G. coropinae), and one (G. chaviro) endemic to southwestern Amazonia. We also diagnose and describe two new species that are endemic to the Upper Madeira basin: G. eyra n. sp., morphologically most similar to G. mamiraua from lowland Amazonia, and G. riberalta n. sp., morphologically most similar to G. pantanal from the Paraguay-Paraná basin. The five Gymnotus species from the Upper Madeira basin are not monophyletic, each species being more closely related to a different species from another region; i.e. the Gymnotus species from the Upper Madeira represents a polyphyletic assemblage. These descriptions to 43 the number of valid Gymnotus species.

Fragmentation of Andes-to-Amazon connectivity by hydropower dams.

Andes-to-Amazon river connectivity controls numerous natural and human systems in the greater Amazon. However, it is being rapidly altered by a wave of new hydropower development, the impacts of which have been previously underestimated. We document 142 dams existing or under construction and 160 proposed dams for rivers draining the Andean headwaters of the Amazon. Existing dams have fragmented the tributary networks of six of eight major Andean Amazon river basins. Proposed dams could result in significant losses in river connectivity in river mainstems of five of eight major systems-the Napo, Marañón, Ucayali, Beni, and Mamoré. With a newly reported 671 freshwater fish species inhabiting the Andean headwaters of the Amazon (>500 m), dams threaten previously unrecognized biodiversity, particularly among endemic and migratory species. Because Andean rivers contribute most of the sediment in the mainstem Amazon, losses in river connectivity translate to drastic alteration of river channel and floodplain geomorphology and associated ecosystem services.

Ictiofauna de la cuenca del río Aguaytía, Ucayali, Perú / Ichthyofauna of the Aguaytía River Basin, Ucayali, Perú

El estudio presenta una lista comentada de especies de peces registradas en la cuenca del río Aguaytía. Son consideradas las colectas de diferentes años y estaciones climáticas entre 1942 y 2009. Es el primer inventario de los peces para esta cuenca, la cual es importante para el Parque Nacional Cordillera Azul. La metodología empleada para la recolección de las muestras incluyó principalmente colectas activas con redes de arrastre de 10x3 m y de 5x2 m y 6 mm de malla. La fijación y preservación de las muestras se realizo con formol al 10% y de etanol al 70%, respectivamente. Las muestras se encuentran en la Colección Ictiológica (MUSM) del Museo de Historia Natural de la Universidad Nacional Mayor de San Marcos. Fueron analizados 9917 ejemplares y registradas un total de 211 especies agrupadas en 28 familias y nueve órdenes

An annotated species fish list recorded in the Aguaytía River basin is presented. Fishes were collected between 1942 and 2009 in different years and seasons. This is the first inventories in Aguaytía river Basin, and for the Cordillera Azúl National Park. Fishes were mainly collected using seines of 10x3 m and of 5x2 m and 6 mm mesh. For fixation and preservation of samples were used 10% formaldehyde solution and 70% ethanol, respectively. Samples are in the Ichthyological Collection (MUSM) of the Museum of Natural History of San Marcos University. We analized 9917 specimens and recorded a total of 211 species of 28 families and nine orders

Revealing Hidden Diversity of the Underestimated Neotropical Ichthyofauna: DNA Barcoding in the Recently Described Genus Megaleporinus (Characiformes: Anostomidae).

Molecular studies have improved our knowledge on the neotropical ichthyofauna. DNA barcoding has successfully been used in fish species identification and in detecting cryptic diversity. Megaleporinus (Anostomidae) is a recently described freshwater fish genus within which taxonomic uncertainties remain. Here we assessed all nominal species of this genus using a DNA barcode approach (Cytochrome Oxidase subunit I) with a broad sampling to generate a reference library, characterize new molecular lineages, and test the hypothesis that some of the nominal species represent species complexes. The analyses identified 16 (ABGD and BIN) to 18 (ABGD, GMYC, and PTP) different molecular operational taxonomic units (MOTUs) within the 10 studied nominal species, indicating cryptic biodiversity and potential candidate species. Only Megaleporinus brinco, Megaleporinus garmani, and Megaleporinus elongatus showed correspondence between nominal species and MOTUs. Within six nominal species, a subdivision in two MOTUs was found, while Megaleporinus obtusidens was divided in three MOTUs, suggesting that DNA barcode is a very useful approach to identify the molecular lineages of Megaleporinus, even in the case of recent divergence (< 0.5 Ma). Our results thus provided molecular findings that can be used along with morphological traits to better define each species, including candidate new species. This is the most complete analysis of DNA barcode in this recently described genus, and considering its economic value, a precise species identification is quite desirable and fundamental for conservation of the whole biodiversity of this fish.

A new species of Chaetostoma, an armored catfish (Siluriformes: Loricariidae), from the río Marañón drainage, Amazon basin, Peru

A new species of Chaetostoma was found in mountain tributaries of the río Marañon, Peru. The new species differs from all described congeners by having a tuft of odontodes, surrounded by naked skin, in the middle of each trunk lateral dermal plate, and in bearing more than 20 hypertrophied evertible odontodes on three cheek plates vs. evenly distributed odontodes on the whole surface of each dermal plate, and in bearing fewer than 20 hypertrophied evertible odontodes on three cheek plates in all other Chaetostoma species. The new species resembles two Cordylancistrus species in the presence of a tuft of odontodes in the middle of each trunk lateral dermal plate, but it exhibits a naked snout (vs. snout covered with plates in Cordylancistrus) and one uniquely derived character present in some species of Chaetostoma - a short, slender fourth branchiostegal ray.

Una distintiva especie de Chaetostoma fue descubierta en los tributarios de montaña del río Marañón, Perú. La nueva especie se diferencia de todas las otras especies de Chaetostoma descritas por tener un mechón de odontodes, rodeado por piel desnuda, en el medio de cada placa dermal lateral del tronco, y más de 20 odontodes hipertrofiados evertibles en tres placas de la mejilla, en contraste con los odontodes distribuidos de forma homogénea sobre toda la superficie de cada placa dermal lateral del tronco, y menos de 20 odontodes hipertrofiados evertibles en tres placas de la mejilla en las demás especies. La nueva especie se parece a dos especies de Cordylancistrus que exhiben un mechón de odontodes en el medio de cada placa dermal lateral del tronco, pero exhibe un hocico desnudo (vs. hocico cubierto por placas en Cordylancistrus) y un caracter derivado único de algunas especies de Chaetostoma - el cuarto radio branquiostego corto y delgado.

Chrysobrycon yoliae, a new species of stevardiin (characiformes: characidae) from the ucayali basin, Peru

Chrysobrycon yoliae, new species, is described from a drainage flowing into the río Yucamia basin, río Ucayali basin, Peru. Chrysobrycon yoliae is readily distinguished from its congeners by the anterior tip of pelvic bone situated anterior to the fifth rib (vs. situated posterior to the fifth rib), the presence of 20-26 dentary teeth (vs. 11-19), and the possession of a terminal lateral-line tube between caudal-fin rays 10 and 11 (vs. the absence of this tube, except in C. eliasi). The new species differs from C. eliasi and C. myersi by the presence of teeth on third pharyngobranchial (vs. the absence of teeth on this bone) and also differs from C. eliasi by the dorsal-fin origin situated at vertical through anal-fin rays 5 to 7 (vs. located at vertical through anal-fin rays 8 to 10), the posterior extent of the ventral process of quadrate reaching the vertical through posterior margin of symplectic (vs. not reaching the vertical through posterior margin of symplectic), the dorsal-fin to adipose-fin length 26.8-28.8% SL (vs. 23.9-26.8% SL), and the body depth at dorsal-fin origin 34.4-42.2% SL (vs. 24.1-34.5% SL). A key for the identification of Chrysobrycon species is provided.

Se describe Chrysobrycon yoliae, una nueva especie de un drenaje que fluye hacia la cuenca del río Yucamia, cuenca del río Ucayali, Perú. Chrysobrycon yoliae es fácilmente distinguible de sus congéneres por la punta anterior del hueso pélvico situada anterior a la quinta costilla (vs. situada posterior a la quinta costilla), la presencia de 20-26 dientes dentarios (vs. 11-19) y la presencia de tubo terminal de la línea lateral entre los radios caudales 10 y 11 (vs. la ausencia de este tubo, excepto en C. eliasi). La nueva especie difiere de C. eliasi y C. myersi por el desarrollo de dientes sobre el tercer faringobranquial (vs. la ausencia de dientes sobre este hueso) y también difiere de C. eliasi por el origen de la aleta dorsal ubicado en la vertical a través de los radios anales 5 a 7 (vs. ubicado en la vertical a través de los radios anales 8 a 10), por la extensión posterior del proceso ventral del cuadrado que alcanza la vertical que pasa por el margen posterior del simpléctico (vs. no alcanza la vertical que pasa por el borde posterior del simpléctico), por la distancia aleta dorsal-aleta adiposa 26,8-28,8% LE (vs. 23,9-26,8% LE) y la altura del cuerpo en el origen de aleta dorsal 34,4-42,2% LE (vs. 24,1-34,5% LE). Se provee una clave para la identificación de las especies de Chrysobrycon.