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We assessed the impact of a modified flood pulse on the trophic ecology of Ilisha amazonica by analyzing diet and resource assimilation through stable isotope analysis (δ13C and δ15N). Collections were conducted monthly between December 2020 and November 2021 in the Xingu River, Amazon. Stomach and muscle tissue were extracted for analysis, and both allochthonous and autochthonous resources were collected. Stomach contents of 247 specimens were analyzed and identified. The water flow regime influenced the consumption of aquatic insects, as well as the trophic niche breadth and feeding intensity of I. amazonica. Based on isotopic composition, the primary carbon sources in the species' diet originated autochthonous items, and the species exhibited a higher trophic position during the flood period. These results highlight the influence of the flood pulse, in a reduced flow environment, on the trophic dynamics of I. amazonia. Our results emphasize the importance of comprehending the interplay between consumers and resources, in areas with human influence, where impacts are practically unknown. [ABSTRACT FROM AUTHOR]

Land tenure security (LTS) is important for achieving many sustainable development goals but its influence on forest cover is mixed. The uncertain relationship between LTS and forests is driven, in part, by the moderating influence of other drivers of deforestation. In this paper we illustrate this complex relationship between LTS and forest cover for individual private landholders in the Colombian Amazon. We use household surveys and econometric analysis with matching techniques to examine whether formal land titles and perceptions of LTS influence forest cover. We explore how the effect of a land title on forest cover is moderated by perceptions of LTS, time to markets, and participation in a conservation program. We find that more secure land tenure, on average, has a statistically significant and negative influence on forest cover in our sample. The negative association between LTS and forest cover is stronger when landholders perceive they have secure tenure and are closer to markets. However, we find the negative relationship between land title and forest cover goes away when a landholder participates in a conservation program. While our cross-sectional data and quasi-experimental methods cannot lead to causal statements, our results are in line with many recent studies in the Amazon region, and our household-level data provides important insight regarding drivers of deforestation that moderate the relationship between land title and forest cover. Our results inform the design of future LTS interventions and conservation efforts. [ABSTRACT FROM AUTHOR]

This study describes a new natural hybrid of Catasetum, C. x vilhenense, from the State of Rondônia (Brazil) found in ombrophilous forests near the Roosevelt River. The hybrid shows intermediate morphological features between its parental species, C. ariquemense and C. multifidum, with specific differences in floral morphology and inflorescence structure. We provide detailed data on its habitat, ecology, and geographic distribution, and a photographic plate of the hybrid. Given its restricted range, limited to a single locality with an area of occupancy (AOO) of less than 10 km2, C. x vilhenense may be Critically Endangered (CR) due to habitat loss and fragmentation. An identification key is also proposed for the species and natural hybrids of Catasetum with symmetrical and parallel antennae in the state of Rondônia, contributing to the understanding and classification of this genus in the Amazon forest. [ABSTRACT FROM AUTHOR]

The Amazon biome is home to the largest tropical forest on the planet and has the greatest global biodiversity on Earth. Despite this, several less charismatic taxonomic groups, such as amphibians, lack comprehensive studies on their species richness and spatial distribution in the Amazon Region. In this study, we investigated: i) patterns of richness and endemism of Amazonian amphibians across geopolitical and biogeographic divisions, ii) similarities between different Amazonian bioregions, iii) temporal trends in amphibian sampling, iv) conservation status of amphibians according to assessments of the IUCN and v) the importance of diverse data sources in building a robust database of amphibian occurrences. We aggregated data from four different sources: publicly accessible platforms, peer-reviewed articles, grey literature and fieldwork inventories spanning 15 years (2007–2021), ultimately compiling 160,643 records of 947 species across 7,418 sampled sites. The greatest diversity of species was found in Peru, Brazil and Ecuador, with notable amphibian diversity and endemism in regions such as the western basins and the Tapajós River Basin in the central-southern Amazon. Geographical analysis of species diversity revealed four distinct groups defined by latitudinal (the Amazon River) and longitudinal (the Juruá, Madeira and Tapajós Rivers) gradients, with low species similarity (< 40%), particularly in the basins of north-western Amazonia. Amphibian sampling in the Amazon has intensified since the 1950s with the establishment of important research centres such as INPA and the GOELD Museum in the Brazilian Amazon. Approximately 18% of Amazonian amphibian species face extinction risk, according to IUCN assessments, highlighting the need for comprehensive data sources to understand and conserve species in this megadiverse region. Our findings suggest that river systems likely influence Amazonian amphibian species composition due to biogeographic history, emphasising the need for robust taxonomic and spatial databases. This study, therefore, contributes a valuable large-scale dataset for Amazonian amphibians, guiding future research and strategies for amphibian conservation.

Malaria is increasingly diagnosed in urban centers across the Amazon Basin. In this study, we combined repeated prevalence surveys over a 4-year period of a household-based random sample of 2,774 persons with parasite genotyping to investigate the epidemiology of malaria in Mâncio Lima, the main urban transmission hotspot in Amazonian Brazil. We found that most malarial infections were asymptomatic and undetected by point-of-care microscopy. Our findings indicate that as malaria transmission decreases, the detection threshold of microscopy rises, resulting in more missed infections despite similar parasite densities estimated by molecular methods. We identified genetically highly diverse populations of Plasmodium vivax and P. falciparum in the region; occasional shared lineages between urban and rural residents suggest cross-boundary propagation. The prevalence of low-density and asymptomatic infections poses a significant challenge for routine surveillance and the effectiveness of malaria control and elimination strategies in urbanized areas with readily accessible laboratory facilities.

Identifying the migration routes and stopover sites used by declining species is critical for developing targeted conservation actions. Long-distance migratory shorebirds are among the groups of birds declining most rapidly, yet we frequently lack detailed knowledge about the routes and stopover sites they use during their hemisphere-spanning migrations. This is especially true for species that migrate through mid-continental regions in the Western Hemisphere. We therefore used satellite transmitters to track 212 individuals of 6 shorebird species during their southward migrations— Pluvialis dominica (American Golden-Plover), Limosa haemastica (Hudsonian Godwit), Tringa flavipes (Lesser Yellowlegs), Calidris subruficollis (Buff-breasted Sandpiper), C. melanotos (Pectoral Sandpiper), and Bartramia longicauda (Upland Sandpiper)—as they crossed the Amazon Basin of South America, a region from which reports of shorebird numbers are increasing but remain relatively rare. Our results make clear that the Amazon Basin provides stopover habitat for a large number of shorebirds: more than 74% of individuals tracked crossing the Amazon Basin stopped over in the region for an average of 2–14 days, with some spending the entire nonbreeding season there. All species selected stopover sites along the region's many rivers and lakes, while within stopover sites each species exhibited distinct habitat preferences. The timing of stopovers within sub-basins of the Amazon Basin also coincided with periods of low water, when the muddy, shallow water habitats preferred by most shorebirds are likely plentiful. Together, our results highlight the need for detailed investigations into shorebird abundance and distribution within the Amazon Basin, threats to shorebirds within particular subbasins, and links between shorebird conservation efforts and those targeting the myriad other species that inhabit this dynamic, hyper-diverse region. [ABSTRACT FROM AUTHOR]

Despite the importance of freshwater ecosystems to social‐ecological systems of the Amazon, conservation in the region historically has focused on terrestrial ecosystems. Moreover, current information on pressing management and conservation needs specific to freshwaters is scattered across multiple disciplines and generally focused on particular threats, habitats, and taxa. This disparateness of information limits the ability of researchers and practitioners to set priorities and implement actions that comprehensively address challenges faced by freshwater ecosystems. To reduce this research‐implementation gap, we reviewed the scientific literature on Amazon freshwater conservation to identify pressing actions to be taken and potential directions for their implementation. We identified 63 actions gleaned from 174 publications. These were classified into six major themes: (i) implement environmental flows, (ii) improve water quality, (iii) protect and restore critical habitats, (iv) manage exploitation of freshwater organisms, (v) prevent and control invasive species, and (vi) safeguard and restore freshwater connectivity. Although each action may face different implementation challenges, we propose three guiding principles to support action planning and decisions on‐the‐ground. We conclude with a reflection on potential future directions to place freshwaters into the center of policies and agreements that target the conservation of the Amazon. [ABSTRACT FROM AUTHOR]

The diurnal cycle of precipitation in the Amazon Basin (AB) is not homogeneous, varying in its intensity, time of occurrence of precipitation peaks and in the shape of its diurnal distribution. This study presents a seasonal characterization of the mean diurnal cycle of precipitation in the AB from IMERG Final Run (Δx = 0.1° and Δt = 30 min) database from 2001 to 2020. Diurnal and semi-diurnal oscillations were studied by harmonics analysis, i.e., using the first and second harmonics, respectively. Harmonic metrics of normalized amplitude (AN), phase and mean hourly precipitation rate were analyzed. The AN showed pixels within the AB with bimodal/uniform or unimodal distribution associated with the occurrence of two peaks (or none) or a single peak during the day. The phase of the first harmonic shows the time of occurrence of the precipitation rates peaks, as well as the displacement of the precipitation systems. The regionalization of the diurnal cycle was performed using the K-Means technique, showing that AB presents six clusters along its domain based mainly on the phase of the first harmonic. The spatial configuration of clusters showed seasonal variation, being modulated by the South American Monsoon System and the large-scale mechanisms responsible for triggering convection. However, their intensity, the shape of the diurnal distribution and the timing of precipitation peaks are modulated by local factors. [ABSTRACT FROM AUTHOR]

The Amazon biome is home to the largest tropical forest on the planet and has the greatest global biodiversity on Earth. Despite this, several less charismatic taxonomic groups, such as amphibians, lack comprehensive studies on their species richness and spatial distribution in the Amazon Region. In this study, we investigated: i) patterns of richness and endemism of Amazonian amphibians across geopolitical and biogeographic divisions, ii) similarities between different Amazonian bioregions, iii) temporal trends in amphibian sampling, iv) conservation status of amphibians according to assessments of the IUCN and v) the importance of diverse data sources in building a robust database of amphibian occurrences. We aggregated data from four different sources: publicly accessible platforms, peer-reviewed articles, grey literature and fieldwork inventories spanning 15 years (2007–2021), ultimately compiling 160,643 records of 947 species across 7,418 sampled sites. The greatest diversity of species was found in Peru, Brazil and Ecuador, with notable amphibian diversity and endemism in regions such as the western basins and the Tapajós River Basin in the central-southern Amazon. Geographical analysis of species diversity revealed four distinct groups defined by latitudinal (the Amazon River) and longitudinal (the Juruá, Madeira and Tapajós Rivers) gradients, with low species similarity (< 40%), particularly in the basins of north-western Amazonia. Amphibian sampling in the Amazon has intensified since the 1950s with the establishment of important research centres such as INPA and the GOELD Museum in the Brazilian Amazon. Approximately 18% of Amazonian amphibian species face extinction risk, according to IUCN assessments, highlighting the need for comprehensive data sources to understand and conserve species in this megadiverse region. Our findings suggest that river systems likely influence Amazonian amphibian species composition due to biogeographic history, emphasising the need for robust taxonomic and spatial databases. This study, therefore, contributes a valuable large-scale dataset for Amazonian amphibians, guiding future research and strategies for amphibian conservation. [ABSTRACT FROM AUTHOR]

The origin of the Amazon River is formed at the confluence of the Marañón and Ucayali rivers. Remote sensing and detailed hydrodynamics, sediment transport and bed morphology analysis under different hydrological conditions have been applied to understand the control mechanisms of the modern confluence, thus informing about ancient confluences. Results showed that: 1) meandering‐meandering confluences existed when bifurcated meandering channels from the Marañón River joined the meandering Ucayali River, 2) far‐field scale provided the boundary conditions for the near‐field scale processes. In the case of the Marañón River, the spatial frequency and displacement of incoming anabranching structures to the confluence location set the boundary conditions for the near‐field scale. In the case of the Ucayali River, the incoming hydrodynamics and bed morphology are governed by far‐field processes such as the occurrence of cutoffs, 3) high intensity secondary flows at large rivers were observed at far‐ and near‐field scales, where previous studies have reported that secondary flows are weak or nonexistence or mainly found downstream of confluences. Finally, 4) even though the Marañón River is larger compared with the Ucayali River, the confluence hydrogeomorphology is governed by the Ucayali River because of more developed and stronger secondary flows. [ABSTRACT FROM AUTHOR]

French Guiana is a French overseas territory located in northern South America. Here we report the first record of Scarthyla goinorum (Bokermann, 1962) from this territory, which represents a range extension of 450 km northward from the nearest previously known occurrence in Amapá state, Brazil. This is also the first occurrence outside the Amazon Basin and indicates the ability of the species to disperse efficiently to other watersheds possibly via floating rafts drifting along the coast.

The development of fast, cost-effective, non-invasive, and efficient sampling alternatives, such as environmental DNA (eDNA), is crucial for understanding the changes in species biodiversity and distributions worldwide, particularly for low abundance, cryptic, and threatened species. This study utilized environmental eDNA to analyze the variety of aquatic, semi-aquatic, and terrestrial vertebrates in the Colombian Amazon and Orinoco basins. The study focused on four main subregions: Bojonawi Natural Reserve and adjacent areas (Vichada Department), Sierra de la Macarena National Park and Tillavá(Meta Department), Puerto Nariño and adjacent areas (Amazonas Department), and the Municipality of Solano (CaquetáDepartment). A total of 709 operational taxonomic units (OTUs) were identified across all sampling locations. The Orinoco River had the highest number of fish genera (68), while the Guayabero River had the highest number of tetrapod genera (13). New taxonomic records were found for all locations, with the highest number of previously undetected fish diversity being found in the Bita, Orinoco, and Tillavárivers, compared to traditional surveys. Likewise, the study identified two fish species, four mammal species, and one reptile species as vulnerable. Additionally, four mammal species were identified as endangered, including the giant otter (Pteronura brasiliensis), two subspecies of the Amazon River dolphin (Inia geoffrensis geoffrensis and Inia geoffrensis humboldtiana), and the tucuxi (Sotalia fluviatilis). Standardizing the methodology and improving current DNA sequence databases for the Neotropics is essential to develop future eDNA studies and enhance our understanding of the region's diversity. [ABSTRACT FROM AUTHOR]

Simple Summary: Knowledge about the pollinator species as required to both value and conserve them. This study explores some of the difficulties when assessing a tropical fauna, with a large proportion left unidentified, although generalities about their biology can still be retrieved based on knowledge of the genera and related species. In this first field survey of an entire bee fauna for any part of Peru, we report a total of 1796 bees belonging to 181 species or morphospecies in four families. The taxonomic impediment was pronounced with only 80 species of 181 that could be named. With such a high proportion of undetermined species, it is not possible to adequately compare pollinator communities across different studies, assess historical changes or analyze endemism patterns to document ecology, behavior and evolution of the species and genera. This information is required to provide a sound basis for policymakers to protect habitats for the conservation of native pollinators. [ABSTRACT FROM AUTHOR]

Knowledge regarding the early life history of neotropical fish, although incipient, is crucial for the accurate identification of larvae collected from the natural environment. Such details are important for defining spawning, drift, and nursery areas as well as the reproductive periods of species. Herein, the larval development of Cynodon gibbus was described using morphological, meristic, and morphometric characteristics. Specimens were collected from open water limnetic zones and under macrophyte stands in the Amazon basin from 2010 to 2023. Forty-eight larvae with standard lengths ranging from 5.73 to 21.57 mm were studied. The larvae have a long to very long body, small eyes, and a small head, which progresses to a moderate size in the preflexion stage. Furthermore, the larvae had ample mouths with numerous conical teeth, an oval-triangular swim bladder, overlapping dorsal and anal fins, and the tip of the pectoral fin not reaching the swim bladder. Pigmentation pattern comprised two punctate pigments above the fontanelle, the rectum, and at the lower and upper ends of the caudal peduncle. Various body parts exhibited predominant allometric relationships, reflecting differential developmental rates among them in response to fundamental ecological requirements for survival. The C. gibbus larvae can be identified by a combination of the position of dorsal, anal and pectoral fins, pigmentation pattern, swim bladder shape, and the total number of myomeres (51 to 53). [ABSTRACT FROM AUTHOR]

The genus Pseudacanthicus encompasses eight recognized species so far: P. histrix, P. serratus, P. spinosus, P. fordii, P. leopardus, P. pitanga, P. pirarara, P. major. Only P. pirarara has been formally described from the rio Xingu basin. To address this gap in taxonomic knowledge of the region, a new species of the Pseudacanthicus is described here, aimed at enhancing our understanding of the genus within the rio Xingu basin and contributing to conservation efforts. The new species is primarily found downstream the impact zone of the Belo Monte Hydroelectric Power Plant. It can be promptly diagnosed from congeners by the color pattern of the body dark brown to black with light gray vermicular spots on the dorsal and ventral surfaces, and fins; lower maximum number of teeth in premaxilla and dentary; and other osteological characters. It's worth noting that the ichthyofauna of the Amazonian drainages lacks comprehensive taxonomic and biological information regarding Pseudacanthicus. In this context, unchecked anthropogenic activities are leading to changes in the ecosystem, often resulting in the extinction of species even before they are scientifically addressed. [ABSTRACT FROM AUTHOR]

The floodplain lakes of the Amazon constitute one of the most important aquatic systems in terms of fish biodiversity. These ecosystems are influenced by the flood pulse, which in turn, affects the behaviour of fish communities within this lake ecosystem. In this study, we tested the hypothesis that the facets of taxonomic and functional diversity may be influenced by the conditions of 'patches' of internal habitats, considering the margins and central environments of a floodplain lake in the Amazon. Lake Cujubim, located on the right bank of the Madeira River, was evaluated via fisheries carried out in the high‐water and low‐water phases, during the day and night, and considering two location strata. The results suggest that the absence of significant differences in alpha taxonomic diversity between the two phases may be a possible seasonal mischaracterisation in Lake Cujubim attributed mainly to dam constructions along the Madeira River. Apparently, no major differences occur in the assembly of fish in terms of their taxonomic and functional characteristics, regardless of luminosity. In the strata of the locations, demonstrates noticeable habitat patches, with the margins being bioregions with high incidences of individuals of the Engraulidae family, confirmed by both taxonomic and functional diversity (alpha and beta). It can be seen that, even in connected lakes, there are differentiated metacommunities between the bioregions, thus forming patches of habitat, and that the shores of the lake, especially those located in proximity or distant from the river, are more suitable areas for food and refuge. [ABSTRACT FROM AUTHOR]

Amazonia is believed to harbour the world’s most extensive tropical peatlands, storing significant amounts of carbon and having high value for biodiversity conservation, climate regulation and human welfare. However, a comprehensive assessment is hampered by fragmentary knowledge of the locations of peat-covered areas and this, in turn, prevents their protection and restoration in the face of ongoing anthropogenic destruction. The study reported here reviewed research activities on peatlands in Amazonia, which started with ecological studies in the 1950s. We found a broad and significant thematic increase since 2009, with growing focus first on carbon accumulation and greenhouse gas fluxes then, after 2017, on degradation and conservation, along with a spatial imbalance in favour of the Peruvian lowlands. Hitherto, very little scientific attention has been directed towards the peatlands of western Brazil, the Bolivian lowlands and the Guianas. Most research in Amazonia has been conducted by international institutions with, in recent times, increasing contributions from local institutes and research groups. Nevertheless, research on Amazonian peatlands is still in its early stages, and several scientific questions remain unanswered. Advancing the knowledge base with respect to various scientific disciplines (e.g., ecology, biology, geography, social sciences and economics) is, therefore, essential for understanding how and where peatlands developed, how they are used, which ecosystem services they provide, how climate change will affect them and, finally, what would be the most appropriate conservation, restoration and sustainable use strategies for safeguarding the wellbeing of both peatlands and people. [ABSTRACT FROM AUTHOR]

Mercury contamination from artisanal and small-scale gold mining (ASGM) currently accounts for 37% of the global total, often affecting tropical regions where regulations, if they exist, are often poorly enforced. Ingestion by people and other animals damages the nervous, reproductive, and cognitive systems. Despite the efforts of many organizations and governments to curb mercury releases from ASGM, it is increasing globally. There are many possible interventions, all with significant complexity and cost. Therefore, we recommend taking an established systematic approach to articulate the current situation and construct theories of change (ToC) for different possible interventions for any government or organization trying to solve this problem. Here we present a high-level situation analysis and generic ToC to support a more coordinated approach that explicitly builds upon previous experience to identify organization- and situation-appropriate engagement on this issue. We then illustrate the use of these generic models to construct a specific ToC with a policy-focused entry point. This includes interventions through (1) engagement with the global Minamata Convention on Mercury; (2) support for existing national laws and policies connected to ASGM and mercury contamination; and (3) engagement of indigenous people and local communities with governments to meet the governments' legal obligations. By methodically articulating assumptions about interventions, connections among actions, and desired outcomes, it is possible to create a more effective approach that will encourage more coordination and cooperation among governments and other practitioners to maximize their investments and support broad environmental and socio-political outcomes necessary to address this pernicious problem. [ABSTRACT FROM AUTHOR]

The ability to accurately map tropical wetland dynamics can significantly contribute to a number of areas, including food and water security, protection and enhancement of ecosystems, flood hazard management, and our understanding of natural greenhouse gas emissions. Yet currently, there is not a tractable solution for mapping tropical forested wetlands at high spatial and temporal resolutions at a regional scale. This means that we lack accurate and up-to-date information about some of the world's most significant wetlands, including the Amazon Basin. RadWet-L is an automated machine-learning classification technique for the mapping of both inundated forests and open water using ALOS ScanSAR data. We applied and validated RadWet-L for the Amazon Basin. The proposed method is computationally light and transferable across the range of landscape types in the Amazon Basin allowing, for the first time, regional inundation maps to be produced every 42 days at 50 m resolution over the period 2019–2023. Time series estimates of inundation extent from RadWet-L were significantly correlated with NASA-GFZ GRACE-FO water thickness (Pearson's r = 0.96, p < 0.01), USDA G-REALM lake hight (Pearson's r between 0.63 and 0.91, p < 0.01), and in situ river stage measurements (Pearson's r between 0.78 and 0.94, p < 0.01). Additionally, we conducted an evaluation of 11,162 points against the input ScanSAR data revealing spatial and temporal consistency in the approach (F1 score = 0.97). Serial classifications of ALOS-2 PALSAR-2 ScanSAR data by RadWet-L can provide unique insights into the spatio-temporal inundation dynamics within the Amazon Basin. Understanding these dynamics can inform policy in the sustainable use of these wetlands, as well as the impacts of inundation dynamics on biodiversity and greenhouse gas budgets. [ABSTRACT FROM AUTHOR]

Simple Summary: Neotropical electric fish have a large diversity in the Amazon region. We investigated the karyotype of the species Brachyhypopomus brevirostris from two localities in Brazil's northern region, Santarém in Pará state and Tefé in Amazonas state, using classical and molecular cytogenetics. Specimens from both localities presented the same karyotype. These are the first results regarding the distribution of repetitive sequences for B. brevirostris samples from the Tefé locality, and the first karyotypic description for the Santarém locality. These results differ from those previously described for samples from Humaitá (Amazon state). This karyotypic difference suggests that the Humaitá sample belongs to another species, which is reinforced in the recent redescription of the genus Brachyhypopomus. Brachyhypopomus (Hypopomidae, Gymnotiformes) is a monophyletic genus consisting of 28 formally described species. Karyotypic data are available for 12 species. The same karyotype is described for two species (B. brevirostris and B. hamiltoni), as well as different karyotypes for the same species from distinct locations (B. brevirostris). In this context, B. brevirostris may constitute a cryptic species complex. Thus, in the present study, we analyzed the karyotype of B. brevirostris, from Santarém, Pará, and Tefé, Amazonas, using classical cytogenetics (conventional staining and C-banding) and molecular techniques (fluorescence in situ hybridization using 18S rDNA, 5S rDNA, U2 snRNA, and telomeric probes). The results show that samples from both locations present 2n = 38, with all chromosomes being acrocentric (FC = 38a). In both populations, 18S rDNA sequences are present on only one pair of homologous chromosomes and telomeric sequences occur only at the ends of the chromosomes. In the Tefé sample, the 5S rDNA occurs in two pairs, and the U2 snRNA in three pairs. These results are the first descriptions of these sequences for B. brevirostris samples from the Tefé locality, as well as the first karyotypic description for the Santarém locality. Future cytotaxonomic studies of this genus can benefit from these results. [ABSTRACT FROM AUTHOR]

Fish growth is a fundamental biological process driven by a multitude of intrinsic (within-individual) and extrinsic (environmental) factors that underpin individual fitness and population dynamics. Interannual variability in river hydrology regarding the intensity and duration of floods and droughts can induce interannual variations in the biotic and abiotic variables that regulate fish growth. However, the understanding of how interannual variability in river hydrology affects fish growth remains limited for most species and ecosystems. We evaluated how inter-annual hydrological variations within the Amazon River basin influence the growth of the catfish Pseudoplaystoma fasciatum. Our research questions were as follows: Do floods lead to the faster growth of P. fasciatum and droughts lead to the slower growth? And do floods and droughts affect all age classes in the same manner? We sampled 364 specimens of P. fasciatum from five sites in the Amazon basin, estimated their growth rates, and related the growth rates to indices of the intensity of floods and droughts. We fitted linear mixed-effects models to test the relationship between growth increments and hydrological indices (with F and D quantifying the intensities of floods and droughts, respectively), age as fixed effects, and basins and Fish ID as random effects. We found an inverse relationship between the increment width in the fish hard parts and hydrological indices. That is, intense floods and droughts negatively affected the growth rates. We also found that the growth of P. fasciatum was no different in years with intense and mild floods across age classes 1–5, although was different for age class 6. However, the growth of P. fasciatum was faster in years of mild droughts for all age classes. Our results showing that the growth of P. fasciatum was slower in years of intense droughts are supported by those of previous studies in the Amazon basin and elsewhere. However, our results showing for the first time that the growth of P. fasciatum is slower in years of intense flooding is the opposite of patterns found in other studies. These results thus suggest that the growth of P. fasciatum is maximized within an optimum range of hydrological conditions, where neither floods nor droughts are intense. [ABSTRACT FROM AUTHOR]

Three new species of Hesperiidae from French Guiana are described. Emmelus benmesbahi Shuey, n. sp. (Eudaminae) represents an eastern extension of this previously monotypic genus. It looks very similar to Emmelus purpurascens but has distinctive genitalia. Damas woldi Shuey, n. sp. (Hesperiinae) is closely related to the widespread neotropical "Damas clavus", a species concept that likely includes other cryptic species across its expansive range. The new species differs consistently in wing pattern and genitalic characters with neighboring populations in the Amazon basin. Metrocles nigroalbum Shuey, n. sp. (Hesperiinae) is a uniquely patterned species that can be confused with no others. All three new species are from the Kaw Mountains and coastal areas of the country. [ABSTRACT FROM AUTHOR]

Land tenure security (LTS) is important for achieving many sustainable development goals but its influence on forest cover is mixed. The uncertain relationship between LTS and forests is driven, in part, by the moderating influence of other drivers of deforestation. In this paper we illustrate this complex relationship between LTS and forest cover for individual private landholders in the Colombian Amazon. We use household surveys and econometric analysis with matching techniques to examine whether formal land titles and perceptions of LTS influence forest cover. We explore how the effect of a land title on forest cover is moderated by perceptions of LTS, time to markets, and participation in a conservation program. We find that more secure land tenure, on average, has a statistically significant and negative influence on forest cover in our sample. The negative association between LTS and forest cover is stronger when landholders perceive they have secure tenure and are closer to markets. However, we find the negative relationship between land title and forest cover goes away when a landholder participates in a conservation program. While our cross-sectional data and quasi-experimental methods cannot lead to causal statements, our results are in line with many recent studies in the Amazon region, and our household-level data provides important insight regarding drivers of deforestation that moderate the relationship between land title and forest cover. Our results inform the design of future LTS interventions and conservation efforts.

The diurnal cycle of precipitation in the Amazon Basin (AB) is not homogeneous, varying in its intensity, time of occurrence of precipitation peaks and in the shape of its diurnal distribution. This study presents a seasonal characterization of the mean diurnal cycle of precipitation in the AB from IMERG Final Run (∆x = 0.1° and ∆t = 30 min) database from 2001 to 2020. Diurnal and semi-diurnal oscillations were studied by harmonics analysis, i.e., using the first and second harmonics, respectively. Harmonic metrics of normalized amplitude (AN), phase and mean hourly precipitation rate were analyzed. The AN showed pixels within the AB with bimodal/uniform or unimodal distribution associated with the occurrence of two peaks (or none) or a single peak during the day. The phase of the first harmonic shows the time of occurrence of the precipitation rates peaks, as well as the displacement of the precipitation systems. The regionalization of the diurnal cycle was performed using the K-Means technique, showing that AB presents six clusters along its domain based mainly on the phase of the first harmonic. The spatial configuration of clusters showed seasonal variation, being modulated by the South American Monsoon System and the large-scale mechanisms responsible for triggering convection. However, their intensity, the shape of the diurnal distribution and the timing of precipitation peaks are modulated by local factors.

Amazonia is believed to harbour the world’s most extensive tropical peatlands, storing significant amounts of carbon and having high value for biodiversity conservation, climate regulation and human welfare. However, a comprehensive assessment is hampered by fragmentary knowledge of the locations of peat-covered areas and this, in turn, prevents their protection and restoration in the face of ongoing anthropogenic destruction. The study reported here reviewed research activities on peatlands in Amazonia, which started with ecological studies in the 1950s. We found a broad and significant thematic increase since 2009, with growing focus first on carbon accumulation and greenhouse gas fluxes then, after 2017, on degradation and conservation, along with a spatial imbalance in favour of the Peruvian lowlands. Hitherto, very little scientific attention has been directed towards the peatlands of western Brazil, the Bolivian lowlands and the Guianas. Most research in Amazonia has been conducted by international institutions with, in recent times, increasing contributions from local institutes and research groups. Nevertheless, research on Amazonian peatlands is still in its early stages, and several scientific questions remain unanswered. Advancing the knowledge base with respect to various scientific disciplines (e.g., ecology, biology, geography, social sciences and economics) is, therefore, essential for understanding how and where peatlands developed, how they are used, which ecosystem services they provide, how climate change will affect them and, finally, what would be the most appropriate conservation, restoration and sustainable use strategies for safeguarding the wellbeing of both peatlands and people.

Incorrect catalogue numbers and incomplete information regarding types of Curimatus Oken of the Naturhistorisches Museum of Vienna (NMW) have been successively replicated in the ichthyology literature. Using evidence compiled directly from NMW types and data, this study formally presents the correct type numbers of Curimatus abramoides Kner 1858 (= Cyphocharax) and Curimatus knerii Steindachner 1876 (= Curimata) and clarifies the taxonomic status and availability of types of Curimatus elegans var. amazonica Steindachner 1911, Curimatus helleri Steindachner 1910, Curimatus surinamensis Steindachner 1910, and Curimatus naegelii Steindachner 1881. [ABSTRACT FROM AUTHOR]

The Amazon River Basin's extraordinary social-ecological system is sustained by various water phases, fluxes, and stores that are interconnected across the tropical Andes mountains, Amazon lowlands, and Atlantic Ocean. This "Andes-Amazon-Atlantic" (AAA) pathway is a complex hydroclimatic system linked by the regional water cycle through atmospheric circulation and continental hydrology. Here, we aim to articulate the AAA hydroclimate pathway as a foundational system for research, management, conservation, and governance of aquatic systems of the Amazon Basin. We identify and describe the AAA pathway as an interdependent, multidirectional, and multiscale hydroclimate system. We then present an assessment of recent (1981 to 2020) changes in the AAA pathway, primarily reflecting an acceleration in the rates of hydrologic fluxes (i.e., water cycle intensification). We discuss how the changing AAA pathway orchestrates and impacts social-ecological systems. We conclude with four recommendations for the sustainability of the AAA pathway in ongoing research, management, conservation, and governance. [ABSTRACT FROM AUTHOR]

A taxonomic revision of Sturisoma is presented. Individuals including both type and non‐type specimens of all valid species were examined. Sturisoma was found to comprise 10 valid species: Sturisoma barbatum, Sturisoma brevirostre, Sturisoma graffini, Sturisoma guentheri, Sturisoma lyra, Sturisoma monopelte, Sturisoma nigrirostrum, Sturisoma reisi, Sturisoma rostratum, and Sturisoma tenuirostre. Furthermore, four new species are described: Sturisoma ghazziae, new species, from the Araguaia River, belonging to the Tocantins‐Araguaia basin, Central Brazil; Sturisoma careirensia, new species, from the middle Amazon basin, Brazil; Sturisoma rapppydanielae, new species, from the Purus River, Amazon basin, Brazil; and Sturisoma defranciscoi, new species, from the Putumayo and Solimões rivers, upper Amazon basin, Colombia, and Brazil. Sturisoma robustum is confirmed as synonym of S. barbatum, species registered along the Paraguay/Parana/La Plata River basin in Argentina, Brazil, and Paraguay. New records were found for S. nigrirostrum as present in the upper Amazon basin, in the Yavari River, Brazil, in addition to its already known locality, the Ucayali River, Peru. The distribution of the type species of the genus S. rostratum is limited to the lower portion of the Amazon basin in the Araguaia, Maranhão, Mearim, Tapajós, and Tocantins rivers and its affluents, Brazil, in contrast to the assumed widespread distribution across the main basins of South America, as previously proposed for the species; the Mearim River is a new record for the species. Updated diagnoses and descriptions are offered for species of Sturisoma, in addition to distribution maps and an identification key for the species. [ABSTRACT FROM AUTHOR]

Presently, Myloplus schomburgkii is the most easily recognized species among the serrasalmids by having a vertical black bar in the middle of the body. However, through a broad taxonomic review, including DNA barcoding and morphological analyses, we were able to identify and describe two new species that also share a dark vertical bar on the flank. In addition, we redescribe M. schomburgkii, designating a neotype and restricting the type-locality to rio Negro in Barcelos, Amazonas State, Brazil. The three lineages of black-barred pacus present high molecular divergences (7.9-11%) and can be distinguished by differences in the shape of the vertical bar, shape of females' anal fin, number of total vertebrae, number of total branched dorsal-fin rays, among other characters. Although the existence of these two new species has been hidden due to many morphological similarities, mainly the presence of the black bar, the three lineages do not compose a monophyletic group, with one of the new species being recovered as sister to Ossubtus xinguense. This result reinforces the necessity of the redefinition of the Myleini genera. [ABSTRACT FROM AUTHOR]

The Brazil Nut tree (Bertholletia excelsa , Lecythidaceae) is a species of considerable historical, economic and ecological importance in South America. Radiocarbon dating indicates some individuals can live from hundreds to more than 1000 years, which means they have the potential to reconstruct deep time growth patterns and their relationship to anthropogenic management or climate change from pre-colonial to present times. However, age estimates vary considerably amongst trees dated with different methods (i.e. tree-ring analysis, radiocarbon-dating, and repeated diameter measurements). Here we analyze living Brazil Nut trees growing in four distinct regions across the Brazilian Amazon using two dating methods: tree-ring counting and radiocarbon dating. Our results show that the congruence between the two methods varies amongst regions, and the highest congruence is found at the site of Tefé, Amazonas. This region features archaeological sites with anthropogenic Terra Preta soils, and is known for its long-term human forest management. This management likely enhanced light and nutrient availability, which possibly enabled the trees to grow at higher rates and form annual rings. Our findings highlight the need for better understanding of the growth of Brazil Nut trees for ecological research, but also the potential of dendrochronology for exploring climate change and human-forest interactions in the Amazon Basin. [ABSTRACT FROM AUTHOR]

The Madeira River presents higher sediment flux in relation to others Amazonian rivers, contributing approximately 45 % of the sediment load to the entire Amazon Basin, that is also the region with the largest untapped hydroelectric potential. The implementation of Jirau and Santo Antonio Dams on Madeira River in Brazil created large run-of-the-river hydroelectric complex, and assessment of silting became an important issue to estimate the actual impact on sediment connectivity and on operation of the reservoir. This paper presents data of the morphology and stratigraphy of a portion of Jirau Reservoir, between the Jirau Rapids and the levees close to the Jirau Dam, in the period of February 8th to February 15th, 2022. The data were obtained by Multibeam Echo Sounder and High-Resolution Seismic Reflection. The results obtained by analysing reservoir bed morphology helped identify regions prone to siltation. The run-of-the-river Jirau Reservoir seems to have had minimal sediment retention since start of operations, as observed in seismic profiles. The suspended sediment concentration map of the study area collected for the year 2021, obtained within a parallel study based on satellite images, showed that the distribution on the surface of the reservoir correlates with the geophysical results, supporting our findings and suggesting the need for joint utilization of geophysical and remote sensing techniques.

The development of fast, cost-effective, non-invasive, and efficient sampling alternatives, such as environmental DNA (eDNA), is crucial for understanding the changes in species biodiversity and distributions worldwide, particularly for low abundance, cryptic, and threatened species. This study utilized environmental eDNA to analyze the variety of aquatic, semi-aquatic, and terrestrial vertebrates in the Colombian Amazon and Orinoco basins. The study focused on four main subregions: Bojonawi Natural Reserve and adjacent areas (Vichada Department), Sierra de la Macarena National Park and Tillavá (Meta Department), Puerto Nariño and adjacent areas (Amazonas Department), and the Municipality of Solano (Caquetá Department). A total of 709 operational taxonomic units (OTUs) were identified across all sampling locations. The Orinoco River had the highest number of fish genera (68), while the Guayabero River had the highest number of tetrapod genera (13). New taxonomic records were found for all locations, with the highest number of previously undetected fish diversity being found in the Bita, Orinoco, and Tillavá rivers, compared to traditional surveys. Likewise, the study identified two fish species, four mammal species, and one reptile species as vulnerable. Additionally, four mammal species were identified as endangered, including the giant otter (Pteronura brasiliensis), two subspecies of the Amazon River dolphin (Inia geoffrensis geoffrensis and Inia geoffrensis humboldtiana), and the tucuxi (Sotalia fluviatilis). Standardizing the methodology and improving current DNA sequence databases for the Neotropics is essential to develop future eDNA studies and enhance our understanding of the region’s diversity.

Deep learning has grown among the prediction tools used within renewable energy options. Solar energy belongs to the options with the lowest atmosphere impact after considering their limitations. In the last five years, Brazil has seen the expansion of wind and solar options almost all over the country, and to preserve the Amazon rainforest, the use of solar energy has helped large and small cities towards a greener future. The novelty of this research covers the use of Deep Learning with data from twelve cities in the state of Amazonas to forecast solar irradiation (W.h/ $\text{m}^{2}$ ) within 30 days. The data input came from ground stations, as much as possible, and NASA satellite models, with a daily time aggregation. The types of neural networks considered are Long Short-Term Memory (LSTM), a Multi-Layer Perceptron (MLP), and an LSTM Gated Recurrent Unit (GRU). Among the metrics used to check the algorithm’s performance, the Mean Absolute Percentage Error (MAPE) indicates that the values of this research are coherent with other scenarios to forecast solar energy; the boundary conditions were not the same, however. The lowest MAPE was observed in the city of Labrea with the LSTM GRU.

The landscape cartography assesses the functional, dynamic, structural and morphological aspects of landscapes, regardless of their taxonomic scale. It seeks to use these units to support environmental and territorial planning and management. Thus, the present study sought to apply this line of analysis to the Pindaré River Basin, precisely in its lower course, located in the Brazilian state of Maranhão. The objective was to identify, classify, map and analyze the landscapes of the lower course through the correlation of variables related to geology, relief, soils, land use and land cover providing data to support and promote preservationist and conservationist public policies and actions in the area. The methodology identified four levels of landscape analysis, from morphometric aspects, geoforms and upper units to reaching the final landscape map, using field output, digital elevation models and satellite images to validate information. The procedures allowed to identify the landscape heterogeneity in a unique environment of saturated and periodically flooded soils contrasting with extensive pastures and little native vegetation. As a result, seven first-level landscape units were identified, coming up to fifty-eight sub-units in the final map. The work aims to apply the methodology in an area of the Maranhão State where few studies on landscape cartography have occurred. The target is to comprehend possible relationships between the functional and structural potential of landscapes and their relationship with the current intensity of land use, contributing to physical- territorial planning permeating geoecological sustainability.

The Amazon Basin is the largest rainforest in the world, and studying the rainfall in this region is crucial for understanding the functioning of the entire rainforest ecosystem and its role in regulating the regional and global climate. This work is part of the application of complex networks, which refer to a network modeled by graphs and are characterized by their high versatility, as well as the extraction of key information from the system under study. The main objective of this article is to examine the precipitation system in the Amazon basin during the austral summer. The networks are defined by nodes and connections, where each node represents a precipitation time series, while the connections can be represented by different similarity functions. For this study, three rainfall networks were created, which differ based on the correlation function used (Pearson, Spearman, and Kendall). By comparing these networks, we can identify the most effective method for analyzing the data and gain a better understanding of rainfall’s spatial structure, thereby enhancing our knowledge of its impact on different Amazon basin regions. The results reveal the presence of three important regions in the Amazon basin. Two areas were identified in the northeast and northwest, showing incursions of warm and humid winds from the oceans and favoring the occurrence of large mesoscale systems, such as squall lines. Additionally, the eastern part of the central Andes may indicate an outflow region from the basin with winds directed toward subtropical latitudes. The networks showed a high level of activity and participation in the center of the Amazon basin and east of the Andes. Regarding information transmission, the betweenness centrality identified the main pathways within a basin, and some of these are directly related to certain rivers, such as the Amazon, Purus, and Madeira. Indicating the relationship between rainfall and the presence of water bodies. Finally, it suggests that the Spearman and Kendall correlation produced the most promising results. Although they showed similar spatial patterns, the major difference was found in the identification of communities, this is due to the meridional differences in the network’s response. Overall, these findings highlight the importance of carefully selecting appropriate techniques and methods when analyzing complex networks.

The relationships and seasonal-to-annual variations among evapotranspiration (ET), precipitation (P), terrestrial water storage anomalies (TWSA), radiation (downward shortwave radiation, DSR), and phenology (leaf area index, LAI) are complex across the Amazon basin. To analyze how ET is controlled by these influencing factors, we used wavelet phase difference (WPD) to investigate the effects of P, TWSA, DSR, and LAI on ET at different spatiotemporal scales. The Amazon-scale averaged ET has strong correlations with these factors at the annual and multi-year periodicities. The patterns of WPDs have south-north and west-east divides due to the significant variation in climatic conditions. The results demonstrate that ET is mainly affected by water and energy availability while vegetation regulates both processes. The deep soil moisture/groundwater can provide strong subsidies to ET during the meteorological dry season in the water-limited area of Amazon. The WPD can well reflect the responses of ET to the variations of P, TWSA, DSR, and LAI, and the process of vegetation sustaining ET in the dry years in the water-limited area of the Amazon.

This paper explores the intricate relationship between the concept of “savage knowledge,” its significance during the ninteenth and twentieth centuries, and the emerging field of ethnoscience. It specifically focuses on the Amazon region as a pivotal area in the development of ethnoscience, examining the contributions of renowned naturalists Carl von Martius, Richard Spruce, and Richard Schultes, who each conducted scientific expeditions to the Amazon during this era. Their works are crucial in reevaluating the dynamic interplay between the Western perception of the “savage,” the scientific principles that underpin it, and the geopolitics of knowledge exchange between countries in the global north and south. I argue that the contextual conditions which made possible the emergence of ethnoscience, including imperial assimilation, extraction, and coloniality, continue to exert influence on twentieth century political discourses concerning the integration of indigenous cultures into global politics. This influence is evident through the analysis of a UNESCO document in the second part of the paper. The study concludes that the incorporation of indigenous knowledge, systematised by ethnoscience, has often served as a pretext for controlling geographical areas historically regarded as “natural resources,” ultimately transforming them into reservoirs of indigenous epistemologies.

The Amazon Basin, which plays a critical role in the carbon and water cycle, is under stress due to changes in climate, agricultural practices, and deforestation. The effects of thermodynamic and microphysical forcing on the strength of thunderstorms in the Basin (75–45°W, 0–15°S) were examined during the pre‐monsoon season (mid‐August through mid‐December), a period with large variations in aerosols, intense convective storms, and plentiful flashes. The analysis used measurements of radar reflectivity, ice water content (IWC), and aerosol type from instruments aboard the CloudSat and CALIPSO satellites, flash rates from the ground‐based Sferics Timing and Ranging Network, and total aerosol optical depth (AOD) from a surface network and a meteorological re‐analysis. After controlling for convective available potential energy (CAPE), it was found that thunderstorms that developed under dirty (high‐AOD) conditions were 1.5 km deeper, had 50% more IWC, and more than two times as many flashes as storms that developed under clean conditions. The sensitivity of flashes to AOD was largest for low values of CAPE where increases of more than a factor of three were observed. The additional ice water indicated that these deeper systems had higher vertical velocities and more condensation nuclei capable of sustaining higher concentrations of water and large hydrometeors in the upper troposphere. Flash rates were also found to be larger during periods when smoke rather than dust was common in the lower troposphere, likely because smoky periods were less stable due to higher values of CAPE and AOD and lower values of mid‐tropospheric relative humidity. Plain Language Summary: The Amazon Basin, which plays an important role in the carbon and water cycle, is under stress due to changes in climate, agricultural practices, and deforestation. The Basin includes a rainforest in the northwest and a mix of deforested areas, savannah‐type vegetation, and agriculture in the southeast. The effects of instability and aerosol loading on thunderstorms in the Basin (75–45°W, 0–15°S) were examined during mid‐August through mid‐December, a period with large variations in aerosols, intense convective storms, and plentiful flashes. The analysis used measurements of radar reflectivity, ice water content (IWC), and aerosol type from instruments aboard the CloudSat and CALIPSO satellites, flash rates from the ground‐based Sferics Timing and Ranging Network, and AOD from a surface network and a meteorological re‐analysis. After controlling for convective available potential energy, a measure of instability, it was found that thunderstorms that developed under dirty (high‐AOD) conditions were approximately 1.5 km deeper, had 50% more IWC, and more than two times as many flashes as storms that developed under clean (low‐AOD) conditions. Flash rates were also found to be larger during periods when smoke rather than dust was common in the lower troposphere, likely because these periods were less stable. Key Points: After controlling for convective available potential energy (CAPE), thunderstorms developing in dirty environments are 1.5 km deeper than storms developing in clean environmentsControlling for CAPE, upper tropospheric ice water content is 50% greater for storms developing in dirty conditions versus clean conditionsAfter controlling for CAPE, flash rates are a factor of two or more greater for storms developing in dirty conditions versus clean conditions [ABSTRACT FROM AUTHOR]

This study presents a 35-year record of total mercury (Hg) concentrations in the detritivore fish Prochilodus nigricans (Curimatã) and the carnivore Cichla pleiozona (Tucunaré), two of the most widely distributed, ecologically important and consumed fish species in the upper Madeira River Basin in the Western Brazilian Amazon. Fish samples from the major Madeira River and marginal lakes and tributaries were compared. Irrespective of site, Hg concentrations were higher in the carnivore fish compared to the detritivore. Hg concentrations increased 5-fold in C. pleiozona in the past three decades, whereas they remained relatively constant in P. nigricans when analyzing the entire 35-year period. When analyzed separately, fish in the main river and marginal lake and tributaries presented the same pattern of Hg variation, with a significant increase in Hg concentrations in the carnivore and in the detritivore in marginal lakes and tributaries but not in the main river. This was in line with the increase in methyl-Hg production in tributaries, mostly associated with deforestation in the past decade in the basin. Although an increase in direct emissions from artisanal gold mining also occurred in the past decade, this caused virtually no impact on fish Hg concentrations, suggesting atmospheric emission and deposition in forests and further export to water systems as an intermediate link with fish Hg concentrations. [ABSTRACT FROM AUTHOR]

Background Theobroma grandiflorum (Malvaceae), known as cupuassu, is a tree indigenous to the Amazon basin, valued for its large fruits and seed pulp, contributing notably to the Amazonian bioeconomy. The seed pulp is utilized in desserts and beverages, and its seed butter is used in cosmetics. Here, we present the sequenced telomere-to-telomere genome of cupuassu, disclosing its genomic structure, evolutionary features, and phylogenetic relationships within the Malvaceae family. Findings The cupuassu genome spans 423 Mb, encodes 31,381 genes distributed in 10 chromosomes, and exhibits approximately 65% gene synteny with the Theobroma cacao genome, reflecting a conserved evolutionary history, albeit punctuated with unique genomic variations. The main changes are pronounced by bursts of long-terminal repeat retrotransposons at postspecies divergence, retrocopied and singleton genes, and gene families displaying distinctive patterns of expansion and contraction. Furthermore, positively selected genes are evident, particularly among retained and dispersed tandem and proximal duplicated genes associated with general fruit and seed traits and defense mechanisms, supporting the hypothesis of potential episodes of subfunctionalization and neofunctionalization following duplication, as well as impact from distinct domestication process. These genomic variations may underpin the differences observed in fruit and seed morphology, ripening, and disease resistance between cupuassu and the other Malvaceae species. Conclusions The cupuassu genome offers a foundational resource for both breeding improvement and conservation biology, yielding insights into the evolution and diversity within the genus Theobroma. [ABSTRACT FROM AUTHOR]

A new species of Moenkhausia from the rio Culuene, rio Xingu basin, in Mato Grosso State is described here through genetic and morphological data. This new species differs from all congeners by the following combination of characters: the presence of reddish color on the posterior portion of the body, as well as on the base of anal, adipose, and pelvic fins in live specimens; a conspicuous midlateral dark stripe, which extends from posterior margin of opercle to the middle of caudal-fin rays, becoming wider and more conspicuous from the vertical through the dorsal-fin origin; absence of humeral blotch; absence of blotches on caudalfin lobes; by having the concentration of dark pigments on the anterior margin of the caudal-fin rays; and presence of 2-3 maxillary teeth. A brief discussion about its putative relationships with other congeners is presented. [ABSTRACT FROM AUTHOR]