Araguaia Research Articles

Eriocaulon benedictum and E. naviculum (Eriocaulaceae): Two New Species from the Brazilian Cerrado

Abstract— Two new species of Eriocaulon (Eriocaulaceae) from the Brazilian Cerrado are described and illustrated. Eriocaulon benedictum, found in the Tocantins River Basin and Plate River Basin has a vegetative morphology similar to Eriocaulon aquatile and E. modestum due to the submerged life form with submerged leaves and long scapes surpassing the water column, but differs from both by the presence of a submerged stem with spiral leaves (vs. a rhizome with rosulate leaves), obtrullate floral bracts (vs. oblong floral bracts in E. aquatile or obovate in E. modestum), and band shaped projections on the seeds (vs. post shaped projections on E. modestum or projections absent in E. aquatile). Eriocaulon naviculum, found in the Araguaia River Basin, an emergent species, has a floral morphology similar to E. altogibbosum and E. gibbosum due to the presence of gibbous sepals in the pistillate flowers, but differs from both by the grey trichomes on the leaf sheath (vs. translucent trichomes in the latter species), slightly sinuous scapes (vs. straight scapes in the latter species), membranous, gibbous swelling in the sepals of the pistillate flowers (vs. incrassate gibbous swelling in the latter species), and seeds without projections with a rough lumen (vs. seeds without projections with a smooth lumen in E. gibbosum or seeds with band-like projections in E. altogibbosum). Detailed descriptions, including anatomical and seed data, illustrations, and maps of occurrence are presented for the new species, as are data on the ecology, geographic distribution, and risk assessments. An updated key for Eriocaulon species from the Tocantins-Araguaia River Basin is also provided.

Flow variability in the Araguaia River Hydrographic Basin influenced by precipitation in extreme years and deforestation

The climatic extremes and the dynamics of land use and cover can cause changes in river flow. The objective of this work was to analyze the flow of the Araguaia River under the effects of extreme years associated with the dynamics of land use in the Araguaia Watershed (AW) from 1981 to 2019. The land use and land cover product were based on the MapBiomas Project classification, imported from the Google Earth Engine. The measured rainfall and flow data were obtained from the National Water Agency. In contrast, the estimated rainfall was based on the data Climate Hazards Group InfraRed Precipitation with Stations. The precipitation climatology showed the lowest values (1,464.9–1,720.4 mm) in the south-central sector, and the highest (1,720.4–2,014.6 mm) rainfall amounts were observed in the north sector. However, it was identified in the five pluviometric stations with a high variability of precipitation, with an emphasis on the extreme years. Such wet and dry years were marked by a large difference in water availability. There was an intense reduction of the Amazon and Cerrado biomes by 31,641.8 and 42,618.9 km², respectively, mainly due to the expansion of 18,936.1 km² of agricultural activities and 47,494 km² of pasture. The fluviometric variability showed a decreasing trend, mainly in the past 15 years. Public actions, such as the intensification of environmental policies, monitoring focusing on the most compromised and strategic areas such as the headwaters of the Araguaia River, can minimize the impacts caused by climate extremes and deforestation.

Taxonomy of the armored catfish genus Aspidoras (Siluriformes: Callichthyidae) revisited, with the description of a new species

Abstract Aspidoras comprises 25 species currently considered as valid, being widely distributed in Brazil, occurring from the upper rio Paraná basin in São Paulo to coastal basins of Ceará. After Nijssen, Isbrücker’s review more than 40 years ago, no extensive work regarding the taxonomy of Aspidoras was conducted. Our paper presents a comprehensive taxonomic revision of the genus, based primarily on the extensive material that has been collected since then. Considering the new diagnosis plus the available phylogenetic data, A. pauciradiatus and A. virgulatus are transferred to Corydoras and Scleromystax, respectively. New synonymies are proposed: A. eurycephalus and A. taurus with A. albater; A. menezesi and A. spilotus with A. raimundi; and A. microgalaeus and A. marianae with A. poecilus. Additionally, a new species from the Araguaia and Paraguay river basins is described, which can be distinguished from its congeners by the morphology of its complex vertebra and infraorbital 1. Thereby, the number of valid species within Aspidoras was reduced from 25 to 18. Redescriptions for A. albater, A. belenos, A. depinnai, A. fuscoguttatus, A. lakoi, A. maculosus, A. poecilus, A. psammatides, A. raimundi, and A. velites are provided. An identification key to the species of Aspidoras is also provided.

Environmental heterogeneity drives the distribution of copepods (Crustacea: Copepoda) in the Amazon, Araguaia, Pantanal, and Upper Paraná floodplains.

Environmental heterogeneity influences the physiology and behavior of organisms, leading to alterations in populations, communities, and ecosystems. This study was designed to evaluate the effect of the spatial and temporal limnological heterogeneity on the distribution of copepods in the Amazon River floodplain, Araguaia River floodplain, Pantanal floodplain, and Upper Paraná River floodplain. We performed dispersion homogeneity tests (PERMIDISP) to analyze the limnological heterogeneity, a Generalized Linear Mixed Model (GLMM) to test the relationship between limnological heterogeneity and species distribution, and a Canonical Correspondence Analysis (CCA) to analyze which limnological variables explain the variation in the community composition. In our study, we observed higher environmental heterogeneity during dry periods, especially in the Amazon floodplain. The Amazon showed the highest species richness (the total number of species that occurred in each floodplain), with endemic species, also the highest abundance of individuals, especially during dry periods, which was possibly due to the biogeography, the size of the basin, and the heterogeneity of the environments. The Pantanal presented the second highest species richness and showed the highest species richness and abundance of individuals during rainy periods. The distribution of copepods was highly correlated with environmental heterogeneity. The species were mainly related to temperature, nutrients, and depth.

A relação entre distribuição regional e abundância de espécies zooplanctônicas numa planície de inundação é mediada pelo regime hidrológico

Abstract: Aim Positive relationships between occupancy and abundance are often found for different groups of organisms and ecosystem types. However, to our knowledge, no study has sought to assess this relationship considering a context in which a particular mechanism is the most likely explanation. In this study, in addition to the positive relationship with abundance, we tested the hypothesis that occupancy of zooplankton species should be greater during the flood season because in this period the hydrological connectivity is greater than in the dry season, facilitating passive dispersal between floodplain environments. Methods Our study was carried out at 52 sites - including lakes and rivers - on the Araguaia River floodplain. We used an analysis of covariance to test the effects of abundance and hydrological period on zooplankton occupancy. Results We found, as expected, a positive relationship between occupancy and abundance of zooplankton species in each hydrological period. Our results also indicated that, with the increase in abundance, species occupancies were higher in the flood than in the dry season. Conclusions The positive effect of the flood on zooplankton occupancy can be explained by the increase in water level that increases the hydrological connectivity and the potential for plankton passive dispersal.

Modern and fossil pollen record from region of the middle Araguaia River floodplain, Tocantins State (Brazil)

The Araguaia river is one of the most important hydrographic basin in Brazil. Its drainage system reaches two dominant Brazilian biomes that are Amazon Rainforest and Brazilian Cerrado (savanna). This study was carried out in a zone of ecotone between rainforest and savanna formations, in the Middle Araguaia River basin, specifically at the floodplain of Javaés River its tributary by right margin, in the State of Tocantins. The goal of this present study was to provide information about the vegetational succession in this forest-savanna ecotone area, in order to contribute to the understanding of this landscape dynamics. For this reason, a sedimentary core collected from a lake (Lago da Mata Verde) was submitted to palynological and radiocarbon dating analyses. The results showed that during the last 400 years this site was bordered by forest reflecting a wet climate with some increase of the flooded margins in the present day. The modern pollen rain and local vegetation data supported in the interpretation of the fossil pollen results. Our findings are according to other studies carried out in the similar ecotone zones and floodplains in Amazonian regions during the Late Holocene.Keywords. Lacustrine sediments, Late Holocene, pollen analysis. Resumo. O rio Araguaia constitui uma das mais importantes bacias hidrográficas brasileiras. Seu sistema de drenagem atravessa dois dominantes biomas brasileiros a saber o bioma Amazônico e o Cerrado brasileiro (savanas). Este estudo, foi realizado em uma zona de ecótono entre as formações de floresta tropical e savana, na bacia do Médio Rio Araguaia, especificamente na planície de inundação do rio Javaés, seu tributário pela margem direita, no estado do Tocantins. O objetivo deste estudo foi fornecer informações sobre a sucessão vegetal nesta área de ecótono floresta-savana, visando contribuir para o entendimento da dinâmica desta paisagem. Dessa forma, um testemunho sedimentar coletado no Lago da Mata Verde foi submetido às análises palinológicas e de datação radiocarbônica. Os resultados mostraram que durante os últimos 400 anos este ambiente foi cercado por floresta refletindo um clima úmido, com um ligeiro aumento de margens inundadas nos dias atuais. Os dados de chuva polínica atual e de vegetação local fundamentaram a interpretação dos resultados palinológicos fósseis. Os resultados obtidos são similares a outros estudos realizados em outras áreas de ecótonos e planícies de inundação em regiões da Amazônia durante o Holoceno Tardio.Palavras-chave. Sedimentos lacustres, Holoceno Tardio, análises palinológicas

Socioeconomic efficiency of the Araguaia River Valley – Goiás: a deterministic frontier and Malmquist index approach

The present study aimed to evaluate socioeconomic efficiency in 41 Brazilian municipalities in the years 2014 and 2016 in the area comprised by the Araguaia River Valley, in the Central-West, Goiás state, Brazil. We used the data envelopment analysis and Malmquist index methods to estimate municipality efficiency and its intertemporal variation. In the frontier model, average income, per capita GDP, and average agricultural income were used as input, and for outputs, the following Municipality Performance Indexes: MPI-Work, MPI-Formal Work, MPI-per capita GDP, and MPI-Agriculture. Results obtained showed a desirable socioeconomic efficiency advance in municipalities, related to a period when agriculture impacted positively on indexes of productivity, per capita GDP, population's average gains, and municipal development index (MPI), with average efficiency in 2014 at 0.92 and 0.93 in 2016. The number of municipalities for each sample that obtained Malmquist index with Mₒ> 1 progress was higher than that with regression (Mₒ <1). Results are relevant considering the novelty in the analysis and show, in the period studied, the productivity and efficiency dynamics in municipalities as for inclusive and sustainable economic and social growth of a region so important in Brazil's Central-West context, and can aid effectively public policies for the Araguaia River Valley, in the state of Goiás, Brazil.

A new candiru of the genus Paracanthopoma (Siluriformes: Trichomycteridae) from the Araguaia River basin, central Brazil.

A new species of the candiru genus Paracanthopoma is described from the floodplains of the Bananal Island, a transition area between the Cerrado and Amazon, in the Araguaia River basin, central Brazil. Paracanthopoma cangussu sp. nov. is distinguished from its congeners, Paracanthopoma parva and Paracanthopoma saci, by the presence of seven opercular odontodes, five dentary teeth, five median premaxillary teeth, and first dorsal-fin pterygiophore in a vertical through the centrum of the 23th or 24th vertebra. It is further distinguished from each congener by an exclusive combination of character states, comprising the number of vertebrae, number of precaudal vertebrae, number of dorsal procurrent caudal-fin rays, number of ventral procurrent caudal-fin rays, number of dorsal-fin rays, disposition of pores on the cephalic portion of the latero-sensory system, absence of an anterior process on the anterior margin of parieto-supraoccipital, number of dorsal-fin pteryigiophores and number of interopercular odontodes. Although vandelliines are known for being exclusively hematophagous, with guts gorged with blood, two cleared and stained specimens of P. cangussu sp. nov. had Chironomidae larvae (Insecta) on their guts. Because most specimens of P. cangussu sp. nov. were collected with stomachs filled with blood, it was hypothesized that the species feeds accidentally or occasionally on insects.

CONSERVATION OF THE ORINOCO GOOSE (NEOCHEN JUBATA) IN THE MIDDLE ARAGUAIA RIVER, TOCANTINS, BRAZIL.

The Orinoco goose, (Neochen jubata) is a grazing herbivore of open habitats that was once widely distributed in tropical South America. Centuries of overhunting and habitat loss have reduced it to widely scattered remnant populations; it is categorized as Near Threatened globally. Within the Cerrado biome, the Middle Araguaia River houses the largest remnant population. In August 2017, a study was started to assess the situation of the Orinoco Goose in the regions of Araguaia National Park, Cantão State Park, and adjacent rice fields. We conducted counts from an aerial census (a 700 km transect), monthly boat censuses (40 km) and land censuses in rice plantations. The aircraft census counted 367 individuals in August 2017, while monthly monitoring of a stretch of the lower Javaés River over more than two years showed a seasonal population variation associated with the flood regime, with the species virtually disappearing during the flood period between January and April when river beaches are submerged. During this period, large flocks of about 1,000 Orinoco Geese were discovered not far away, concentrated in small stretches of rice plantation agro-systems in the region. This behavioral seasonal concentration makes the species susceptible to poisoning and epizootic diseases. The findings suggest the need to re-categorize the Orinoco Goose population of the Middle Araguaia River as “Threatened” for the State of Tocantins due to the decline observed in the last 10 years, the maximum estimated population size, and the significant seasonal concentrations in a restricted area. At the same time, it is necessary to develop an action plan for its conservation in the surroundings of Ilha do Bananal, and throughout Brazil, where its threat status must be reviewed.

Recent population differentiation in the habitat specialist Glossy Antshrike (Aves: Thamnophilidae) across Amazonian seasonally flooded forests.

We assessed population structure and the spatio‐temporal pattern of diversification in the Glossy Antshrike Sakesphorus luctuosus (Aves, Thamnophilidae) to understand the processes shaping the evolutionary history of Amazonian floodplains and address unresolved taxonomic controversies surrounding its species limits. By targeting ultraconserved elements (UCEs) from 32 specimens of S. luctuosus, we identified independent lineages and estimated their differentiation, divergence times, and migration rates. We also estimated current and past demographic histories for each recovered lineage. We found evidence confirming that S. luctuosus consists of a single species, comprising at least four populations, with some highly admixed individuals and overall similar levels of migration between populations. We confirmed the differentiation of the Araguaia River basin population (S. l. araguayae) and gathered circumstantial evidence indicating that the taxon S. hagmanni may represent a highly introgressed population between three distinct phylogroups of S. luctuosus. Divergences between populations occurred during the last 1.2 mya. Signs of population expansions were detected for populations attributed to subspecies S. l. luctuosus, but not for the S. l. araguayae population. Our results support that S. luctuosus has had a complex population history, resulting from a high dependence on southeastern “clear water” seasonally flooded habitats and their availability through time. Spatial and demographic expansions toward the western “white water” flooded forests might be related to recent changes in connectivity and availability of these habitats. Our study reinforces the view that isolation due to absence of suitable habitat has been an important driver of population differentiation within Amazonian flooded forests, but also that differences between várzeas (“white water” floodplains, mostly in southwestern Amazonia) and igapós (“clear water” floodplains, especially located in the east) should be further explored as drivers of micro‐evolution for terrestrial species.

Eco-efficiency measurement as an approach to improve the sustainable development of municipalities: A case study in the Midwest of Brazil

Global challenges related to energy consumption, water scarcity, deforestation, and environmental pollution have a direct impact on municipalities in Brazil and other countries around the world. Thus, the present study aims to evaluate eco-efficiency and its determinants in 41 Brazilian municipalities between 2014 and 2016 in the area covered by the Araguaia River Valley, in the Midwest of Brazil, Goiás state region. The Araguaia River Valley is considered of economic and especially environmental importance. It is located in one of the main Brazilian river basins, adjacent to states comprising the Legal Amazon, one of the world's most important biomes. To measure the eco-efficiency rate, we applied Data Envelopment Analysis (DEA) via the model of output-oriented variable returns to scale (VRS). Variables used as input include Energy Consumption, Water Consumption, Number of Inhabitants, Fleet of Vehicles, Territorial Area, Deforested Area, and output is the ratio between GDP per capita and Deforested Area. In the second stage, we used Tobit regression with eco-efficiency rate as the dependent variable. For the analyzed period, results show low mean eco-efficiency in the VRS model, with values of 0.45 (2014) and 0.48 (2016). Results indicate that the municipalities of Castelândia in 2014, and Santo Antônio da Barra in 2016, achieved a sustainable balance between environmental and economic variables, contributing to conservation. That suggests that these municipal areas be a benchmark for the others and to local and national public managers, as well as the effective DEA technology applicability in calculating eco-efficiency. In contrast to these two cases, the Mineiros municipality (Araguaia River headwater area) obtained a very low eco-efficiency score. This is extremely concerning since this is an important and sensitive area in this region. In the second stage of the research, the Tobit model indicates that Deforested Area in 2014 and 2016 was significant and negatively correlated with the dependent variable, while Water Consumption (2016) was positively correlated with eco-efficiency. However, the robustness test shows the significant and negative correlation between Water Consumption and eco-efficiency in both years, additionally, the test confirms the results for the Deforested Area variable. These results are important to support policymakers and public managers in the development of more sustainable and eco-efficient municipalities worldwide.

Estimation of river flow using CubeSats remote sensing

River flow characterizes the integrated response from watersheds, so it is essential to quantify to understand the changing water cycle and underpin the sustainable management of freshwaters. However, river gauging stations are in decline with ground-based observation networks shrinking. This study proposes a novel approach of estimating river flows using the Planet CubeSats constellation with the possibility to monitor on a daily basis at the sub-catchment scale through remote sensing. The methodology relates the river discharge to the water area that is extracted from the satellite image analysis. As a testbed, a series of Surface Reflectance PlanetScope images and observed streamflow data in Araguaia River (Brazil) were selected to develop and validate the methodology. The study involved the following steps: (1) survey of measurements of water level and river discharge using in-situ data from gauge-based Conventional Station (CS) and measurements of altimetry using remote data from JASON-2 Virtual Station (JVS); (2) survey of Planet CubeSat images for dates in step 1 and without cloud cover; (3) image preparation including clipping based on different buffer areas and calculation of the Normalized Difference Vegetation Index (NDVI) per image; (4) water bodies areas calculation inside buffers in the Planet CubeSat images; and (5) correlation analysis of CubeSat water bodies areas with JVS and CS data. Significant correlations between the water bodies areas with JVS (R2 = 88.83%) and CS (R2 = 96.49%) were found, indicating that CubeSat images can be used as a CubeSat Virtual Station (CVS) to estimate the river flow. This newly proposed methodology using CubeSats allows for more accurate results than the JVS-based method used by the Brazilian National Water Agency (ANA) at present. Moreover, CVS requires small areas of remote sensing data to estimate with high accuracy the river flow and the height variation of the water in different timeframes. This method can be used to monitor sub-basin scale discharge and to improve water management, particularly in developing countries where the presence of conventional stations is often very limited.

The biosonar of the boto: evidence of differences among species of river dolphins (Inia spp.) from the Amazon.

Echolocation clicks can reflect the anatomy of the vocalizing animal, enabling the distinction of species. River dolphins from the family Iniidae are formally represented by one species and two subspecies (Inia geoffrensis geoffrensis and I. g. humboldtiana). Additionally, two other species have been proposed (I. boliviensis and I. araguaiaensis) regarding its level of restricted distribution and morph-genetics differences. For the Committee on Taxonomy of the Society for Marine Mammalogy, the specific status of the proposed species relies on further knowledge on morphology, ecology, and genetics. Given that species-specific status is required for conservation efforts, we described and compared the echolocation clicks of Inia spp., searching for specific differences on their vocalizations. The sounds were captured with a Cetacean Research ™ C54XRS (+3/−20 dB, −185 dB re: 1V/μPa) in Guaviare River (Orinoco basin), Madeira River (Madeira basin), Xingu River (Amazon Basin), and Araguaia River (Tocantins-Araguaia basin). We found significant differences in all analyzed parameters (peak frequency, 3 dB bandwidth, 10 dB bandwidth and inter-click interval) for all species and subspecies. Differences in acoustical parameters of clicks are mainly related to the animal’s internal morphology, thus this study may potentially support with information for the species-level classification mostly of I. araguaiaensis (the Araguaian boto). Classifying the Araguaian boto separately from I. geoffrensis has important implications for the species in terms of conservation status, since it is restricted to a highly impacted river system.

Metal bioaccumulation and its genotoxic effects on eggs and hatchlings of giant Amazon river turtle (Podocnemis expansa).

The aim of this study was to assess whether possible metal contamination in the sediment of the nests of giant Amazon river turtle, Podocnemis expansa, could contaminate eggs and hatchlings, triggering genotoxic damage. Therefore, sediments of P. expansa nests from two sites in the Brazilian Amazon were evaluated, with the first being collected at Araguaia River and the second at Crixás-Açu River. Newly hatched offspring, eggs, and sediments were collected from the beaches of these two rivers and the quantification of metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn) was carried out by atomic absorption spectroscopy. All targeted metals were found in both sediment and P. expansa biological samples collected on the beaches presenting higher concentrations in the sediment of Crixás-Açu River. Metals found in the eggshells before nesting and in the egg contents were maternally transferred. Moreover, augmented concentration of metals led by metal transfer from the nests sediments were detected in the eggshells after nesting (ENH) and in the newly hatched offspring (H). Probably this metal relocation to the newly hatchlings augmented the frequency of micronuclei in their blood, presenting 15.25‰ in hatchling found in Crixás-Açu River beaches and 10‰ in newly hatched animals from Araguaia River beaches. These results indicate the occurrence of maternal transfer of metals (essential or not) to the eggs in testudines as well as a transference from the sediments to the nesting eggs, triggering genotoxic effects on the hatchlings.

Terrain units, land use and land cover, and gross primary productivity of the largest fluvial basin in the Brazilian Amazonia/Cerrado ecotone: The Araguaia River basin

Integrity of most of tropical wetlands is threatened because they are often considered freely available resources of land and water. The Bananal, in the Araguaia River Basin, and the Pantanal in the Paraguai River Basin, are the two largest Brazilian wetlands influenced by the tropical seasonal floods. The purpose of this study is to integrate landscape structural and functional factors with the GPP dynamics over different terrain units present in the Araguaia River Basin. The study was conducted through the integration of different databases, including the topographic domains, protected areas and indigenous lands; land use and land cover map (year 2016); time series of GPP derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor (period of 2000–2015); Shuttle Radar Topography Mission (SRTM) digital elevation models (DEM); and precipitation data produced by the WorldClim version 2 dataset. GPP time series were processed using statistical methods of time series decomposition. The results show that, in the alluvial domains, we find grasslands (mostly), alluvial forests with the highest levels of GPP, and the largest legally protected areas. Spatial distribution of pasturelands across the entire basin is broad while croplands are concentrated mainly in geologically old and high plateaus. The time series analysis revealed the presence of intra- and inter-annual vegetation patterns and a continuous increase of GPP over time. The results contribute to the understanding of the linkages between land use changes and global carbon cycles by considering land use as a response of how the landscape is organized. The results may provide subsidies for public policies for the carbon budget equilibrium, conservation of biodiversity, and rational use of natural resources.

Two new species of Knodus (Characidae: Stevardiinae) from the upper rio Tocantins basin, with evidence of ontogenetic meristic changes

ABSTRACT Two new species from the upper rio Tocantins basin are described in Knodus based on the traditional definition of the genus. The new species are distinguished from other congeners by meristic and morphometric characters, such as the number of cusps in the premaxillary and dentary teeth, the number of scale series between dorsal-fin origin and lateral line, the orbital diameter and the body depth. With the two new species, the number of endemic species in the upper rio Tocantins basin upstream of the mouth of the rio Paranã, rises to 53 (89 to the confluence with rio Araguaia). The existence of a meristic character that changes through ontogeny (allomery), viz. the number of scale series between dorsal-fin origin and lateral line, was detected in some species of Knodus through a regression analysis. Additionally, this paper describes an unambiguous, more informative and precise new method for counting vertebrae, which will enhance the efficacy of this trait in species comparisons.

A new species of Satanoperca (Teleostei: Cichlidae) from the Rio Tocantins basin, Brazil

Abstract A new species of Satanoperca is described from the Rio Araguaia, Rio Tocantins basin, Brazil, and non-native records are available in the upper Rio Paraná basin. It differs from congeneric species by color pattern characters, such as head and flank marks. It is included in the Satanoperca jurupari species group, characterized by the absence of black rounded blotches on the flank, and low meristic values. A description of the ontogeny of melanophore marks of the S. jurupari species group revealed two different types of arrangement on the flank and numerous melanophore marks on the head. A discussion on morphologically diverse assemblages in the S. jurupari species group is also provided.

Genetic structure and diversity in Neochen jubata (Aves: Anatidae) from the Araguaia River, GO, Brazil

Abstract: The Orinoco Goose (Neochen jubata) is a few-known and endemic Anatidae to South America, inhabiting sandy beaches along medium and large rivers, with a well-developed riparian forest and in swamp savannas and large freshwater baths. Recent data indicate the presence of longitudinal migratory behavior, and despite them, there are no records on the genetic profile of this species. The Araguaia River region, in the municipality of Luiz Alves, Goiás, receives an undetermined number of ducks seasonally, and there is little information about the individuals who visit this place, constituting the ideal scenario for a study able to offer a genetic overview perspective of this species and to understand the relationship between these individuals better. For this, we genetically characterized 61 individuals sampled in three distinct years of collection using microsatellite molecular markers and mitochondrial DNA. Genetic diversity analyses revealed low levels of heterozygosity for all sampled groups. However, they are within the equilibrium proposed by Hardy-Weinberg (HWE), as inbreeding or drift are not acting in these groups. The parentage analysis supports it, showing a high number of unrelated individuals over the years. AMOVA showed a significant difference among groups. These results may reflect the structure of this migratory species in that region, with the paired differentiation test of individuals from 2013 and 2014 being more similar to each other than those from other years, indicating a possible genetic structure diagnosed by the years of capture. However, there is a high allelic sharing among the three sampled groups, suggesting that these individuals are a population that connects over time and that they have a philopatric relationship with the location. The results found in this study constitute an initial milestone for the genetic knowledge of the mallard duck that should be raised in many other genetic studies.

Contributions to the taxonomy of Trachelyopterus (Siluriformes): comparative cytogenetic analysis in three species of Auchenipteridae

ABSTRACT Auchenipteridae is divided into subfamilies Centromochlinae and Auchenipterinae. Parauchenipterus is included in the latter and is subject of taxonomic discussions concerning its validation or synonymization with Trachelyopterus. Herein, three species from two hydrographic basins were cytogenetically analyzed: Parauchenipterus striatulus from Doce River and two sympatric species, P. galeatus and Trachelyopterus coriaceus, from the Araguaia River. Diploid number of 58 chromosomes was verified for all species, but P. striatulus has different karyotype formula from the others. The three species have heterochromatin located in terminal regions of almost all chromosomes and in pericentromeric region on acrocentric chromosomes. Simple NORs was verified on a subtelocentric chromosome for all species. 5S rDNA sites were detected in three submetacentric chromosome pairs in P. striatulus; in a metacentric chromosome pair and submetacentric pair in T. coriaceus; and in one metacentric chromosome pair in P. galeatus. The similarities found in the karyotypes of the three species suggest the existence of only one genus, Trachelyopterus; therefore, our data refutes the validation of Parauchenipterus. Moreover, the differences in 5S rDNA distribution in P. galeatus in comparison with other populations already studied, indicate the existence of a new taxonomic unit, which suggests a species complex in P. galeatus.

Streams fish from Upper Araguaia and Middle Rio da Mortes basin, Brazil: generating subsidies for preservation and conservation of this critical natural resource

Abstract: The Araguaia River basin has the highest fish biodiversity within the Cerrado biome (Brazilian savannah), with many endemic and threatened species by human activities. Despite growing efforts to catalog Neotropical freshwater fish biodiversity, many regions are still undersampled. Our objective is to complement the information about stream fish in two hydrographic basins in the Cerrado. We sampled 72 streams with 50 m stretch in the Upper Araguaia (n = 32) and Middle Rio das Mortes (n = 40) basins. We collected 14,887 individuals distributed in 137 species, 81 genera, 30 families, and six orders. Characidae, Loricariidae, and Cichlidae were the families richer in species. We found a high diversity of rare fish species in the streams sampled, ca. 71.5% of the species had at least five individuals collected, and 18 species had only one collected specimen. The most frequent species were Astyanax cf. goyacensis, Knodus cf. breviceps, and Characidium cf. zebra. Both basins shared around 43% of the species. We caught 76 species in Upper Araguaia and 120 species in Middle Rio das Mortes. Seventeen exclusive fish species occurred in Upper Araguaia, whereas 61 were found in the Middle Rio das Mortes basin. Our analysis showed lower diversity of fish in Upper Araguaia than in the Middle Rio das Mortes basin. Considering the exclusive fish species of both basins, the human threats in those regions, and the few existent protected areas, we need a better look at the aquatic biodiversity conservation of this ecosystem.