Temperature-dependent sex determination occurs in many species of turtles. Because substrates dif... more Temperature-dependent sex determination occurs in many species of turtles. Because substrates differ in their heat retention capacities, a relatively small change in ambient temperature can exert great influence on sex ratios of hatchlings from clutches deposited in different substrates even within the same geographical area. Since Podocnemis unifilis is one of the Amazonian turtle species (Podocnemididae) with high behavioural plasticity in the use of nesting sites, we tested the influence of soil types on hatchling sex ratios in the Piagaçu Purus Sustainable Development Reserve along the lower Purus River, Brazil. During the 2013 and 2014 nesting seasons, we evaluated 26 nests on a sand bank (n = 14) and clay banks (n = 12). Approximately half of the hatchlings that emerged from each nest were sexed via gonad histological analysis (n = 341). We found a higher incidence of females in nests from the sandy substrate and more males in nests from the clayey substrate (χ2 = 40.466, df =...
Nesting site selection is of great ecological and evolutionary importance for turtles, because it... more Nesting site selection is of great ecological and evolutionary importance for turtles, because it is a key determinant of individual reproductive success. In this study we evaluated the effects of two types of nesting substrate (sand bank and clay banks) on the incubation success of a generalist nesting species, Podocnemis unifilis, in a floodplain area in the Brazilian Amazon. Nesting characteristics were recorded during the nesting seasons of 2012–2014, when 634 nests were monitored throughout the incubation period. Mean size of laying females did not vary between substrate types (sand = 24.71 cm; clay = 25.44 cm; P = 0.2054), nor was clutch size related to females’ sizes. However, females that nested on sand bank exhibited a clearer pattern of nest positioning relative to distances to vegetation and water line than those laying eggs on clay banks. Mean egg size (40.24 ± 2.68 mm) and weight (21.09 ± 5.46 g) did not vary between types of nesting substrate, and there was no variatio...
Revista da Sociedade Brasileira de Medicina Tropical, 2021
The type of catfish referred to as candirus, is a member of the Trichomycteridae and Cetopsidae f... more The type of catfish referred to as candirus, is a member of the Trichomycteridae and Cetopsidae families1,2. The subfamilies Vandelliinae and Stegophilinae (Trichomycteridae) and Cetopsinae (Cetopsidae) are relevant to human medicine, including forensics1,2,3,4. Herein, we present a brief essay on candirus and their relationship with human health and death. We examined published accounts and used our personal observations on the subject.
Rapids and waterfalls, and their associated fauna and flora are in peril. With the construction o... more Rapids and waterfalls, and their associated fauna and flora are in peril. With the construction of each new hydroelectric dam, more rapids and waterfalls are destroyed, leading to the disappearance of associated fauna and flora. Areas of rapids harbor distinct, highly endemic rheophilic fauna and flora adapted to an extreme environment. Rheophilic habitats also have disjunct distribution both within and across rivers. Rheophilic habitats thus represent islands of suitable habitat separated by stretches of unsuitable habitat. In this study, we investigated to what extent, if any, species of cichlid and anostomid fishes associated with rheophilic habitats were structured among the rapids of Araguaia River in the Brazilian Amazon. We tested both for population structuring as well as non-random distribution of lineages among rapids. Eight of the nine species had multiple lineages, five of these nine species were structured, and three of the eight species with multiple lineages showed non-random distribution of lineages among rapids. These results demonstrate that in addition to high levels of endemicism of rheophilic fishes, different rapids even within the same river are occupied by different lineages. Rheophilic species and communities occupying different rapids are, therefore, not interchangeable, and this realization must be taken into account when proposing mitigatory/compensatory measures in hydroelectric projects, and in conservation planning.
The ichthyofauna of the headwaters of the main tributaries of the mighty Solimões/Amazonas River ... more The ichthyofauna of the headwaters of the main tributaries of the mighty Solimões/Amazonas River has been little studied. Considering the importance of those environments for the overall fish diversity in that river system, we surveyed the composition of the fish fauna of the upper portion of Purus River and two of its tributaries (Caeté and Macapá rivers), state of Acre, Brazil. The collections were done in November 2004, using a seine net and a set of gillnets of different mesh sizes. A total of 735 specimens belonging to 86 species and 28 families were collected. Eight species, Creagrutus occidaneus, Phenacogaster pectinatus, Prionobrama filigera, Moenkhausia cf. lepidura, Leptagoniates pi (Characidade), Henonemus punctatus (Trichomycteridae), Toracocharax stellatus (Gateropelecidae), and Eigenmannia macrops (Sternopygidae) composed nearly half of the specimens collected. This survey adds 48 new records to the ichthyofauna of Purus River and elevates to 243 the number of...
Potamotrygonid stingrays are restricted to Neotropical rivers and information on their diet remai... more Potamotrygonid stingrays are restricted to Neotropical rivers and information on their diet remains scarce. Thus, the prey composition of four freshwater stingray species from the middle Negro River was studied using stomach contents analysis: Potamotrygon motoro (n=40), Potamotrygon orbignyi (n=27), Potamotrygon sp. "cururu" (n=26), and Paratrygon aiereba (n=34). Prey items were identified up to the lowest taxonomic level possible and analyzed with the Index of Relative Importance (%IRI). Teleosteans, crustaceans and insect larvae were consumed by all species in distinct proportions. Potamotrygon motoro fed mainly on palaemonid shrimps (33.8%) and trichodactylid crabs (48.7%). Stomach contents of Potamotrygon orbignyi were composed principally by insects (96.4%), with predominance of gomphid dragonfly larvae. Potamotrygon sp. "cururu" fed on crustaceans (shrimps and crabs: 49.4%) and insect larvae (30.2%). Paratrygon aiereba consumed mainly teleosteans (94.8%), ...
Contrasting with most sharks, which mainly use axial and caudal fin movements during locomotion, ... more Contrasting with most sharks, which mainly use axial and caudal fin movements during locomotion, batoids tend to use undulation or oscillation of the pectoral fins as their primarily locomotory mode. Movements by undulation are prevalent in many batoid groups, such as dasyatid and rajid species, whereas oscillatory movements are predominant among more derived stingrays (Rhinopteridae and Mobulidae) (ROSENBERGER & WESTNEAT 1999, ROSENBERGER 2001). Even though the role of the pectoral fins during swimming is well documented in batoids, the specific role of the pelvic fins in the locomotion of many species is unknown. However, they are known to play an important role in swimming and body maneuvering in batoids, especially during benthic locomotion (
Submetido em 22/11/2010 Aceito para publicação em 05/05/2011 Resumo O presente trabalho estudou c... more Submetido em 22/11/2010 Aceito para publicação em 05/05/2011 Resumo O presente trabalho estudou composição e abundância de peixes que realizam movimentos entre os bancos
Due to the existence of terrestrial barriers to freshwater fish dispersion, it is believed that i... more Due to the existence of terrestrial barriers to freshwater fish dispersion, it is believed that its distribution is strongly associated with historical factors related to the formation of the habitats they occupy. By the other hand, some studies reveal the influence of abiotic conditions (such as size of water bodies, pH, conductivity) on the composition of fish fauna occurring in small streams. This study aimed to investigate whether drainage basins, because catchment boundaries are potential barriers to fish dispersion, or the physical structure and physico-chemical characteristics of water have a greater influence on fish community structure in small streams. We sampled 22 streams belonging to five drainage basins in the Madeira-Purus interfluve. Fish were caught with dip nets and a small trawl, and data were simultaneously obtained on structural characteristics of the streams and physico-chemical characteristics of the water. Community composition was analyzed using Non-Metric M...
Biodiversity loss is one of the main challenges of our time and attempts to address it require a ... more Biodiversity loss is one of the main challenges of our time and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost.
ABSTRACTAimCommunity phylogenetics provides important information about the evolutionary and ecol... more ABSTRACTAimCommunity phylogenetics provides important information about the evolutionary and ecological factors help structure regional species assemblages. Here, we analyze phylogenetic diversity (phylodiversity) patterns among fish species in 97 sub-drainages of the Amazon basin, to evaluate the roles of historical and contemporary processes in generating and maintaining the exceptional richness and endemism of Amazonian fish species assemblages.LocationAmazon River basinTaxonFreshwater fishesMethodsUsing a large comprehensive database of freshwater fish species distributions, and a well-sampled molecular phylogeny of ray-finned (actinopterygian) fishes, we develop of multivariate statistical model to correlate estimated historical and contemporary environmental parameters with sub-drainage phylodiversity patterns. The model employs three phylogenetic metrics: i.e.: phylogenetic diversity (PD) sensu stricto, mean pairwise phylogenetic distance (MPD) between species capturing phylo...
Acanthodoras is the only genus of catfish known to secrete a conspicuous and abundant milky-looki... more Acanthodoras is the only genus of catfish known to secrete a conspicuous and abundant milky-looking substance through an axillary pore located just below the base of the posterior cleithral process. Despite this remarkable feature, there is no published information on the anatomical structures that produce the secretion and its possible biological/ecological functions. Dissection and histological analysis of preserved specimens of A. spinosissimus revealed the presence of a saccular axillary gland with large, binuclear secretory cells, similar to those found in other poisonous catfish. Secretory cells near the lumen appear to lose nuclei and become filled with secretory products, possibly with proteinaceous elements, as indicated by their eosinophilic appearance. As far as we know, the saccular morphology of the gland appears to constitute a unique characteristic of Acanthodoras among Doradidae catfishes. Further studies are necessary to determine the chemical composition of the sec...
Ichthyological surveys have traditionally been conducted using whole-specimen, capture-based samp... more Ichthyological surveys have traditionally been conducted using whole-specimen, capture-based sampling with varied but conventional fishing gear. Recently, environmental DNA (eDNA) metabarcoding has emerged as a complementary, and possible alternative, approach to whole-specimen methodologies. In the tropics, where much of the diversity remains undescribed, vast reaches continue unexplored, and anthropogenic activities are constant threats; there have been few eDNA attempts for ichthyological inventories. We tested the discriminatory power of eDNA using MiFish primers with existing public reference libraries and compared this with capture-based methods in two distinct ecosystems in the megadiverse Amazon basin. In our study, eDNA provided an accurate snapshot of the fishes at higher taxonomic levels and corroborated its effectiveness to detect specialized fish assemblages. Some flaws in fish metabarcoding studies are routine issues addressed in natural history museums. Thus, by expan...
Non-native fish (NNF) can threaten megadiverse aquatic ecosystems throughout the planet, but limi... more Non-native fish (NNF) can threaten megadiverse aquatic ecosystems throughout the planet, but limited information is available for the Amazon Region. In this study we review NNF data in the Amazonian macroregion using spatiotemporal records on the occurrence and the richness of NNF from a collaborative network of 35 regional experts, establishing the Amazon NNF database (ANNF). The NNF species richness was analyzed by river basin and by country, as well as the policies for each geopolitical division for the Amazon. The analysis included six countries (Brazil, Peru, Bolivia, Ecuador, Venezuela, and Colombia), together comprising more than 80% of the Amazon Region. A total of 1314 NNF occurrence records were gathered. The first record of NNF in this region was in 1939 and there has been a marked increase in the last 20 years (2000–2020), during which 75% of the records were observed. The highest number of localities with NNF occurrence records was observed for Colombia, followed by Bra...
The Tocantins-Araguaia Basin is one of the largest river systems in South America, located entire... more The Tocantins-Araguaia Basin is one of the largest river systems in South America, located entirely within Brazilian territory. In the last decades, capital-concentrating activities such as agribusiness, mining, and hydropower promoted extensive changes in land cover, hydrology, and environmental conditions. These changes are jeopardizing the basin's biodiversity and ecosystem services. Threats are escalating as poor environmental policies continue to be formulated, such as environmentally unsustainable hydropower plants, large-scale agriculture for commodity production, and aquaculture with non-native fish. If the current model persists, it will deepen the environmental crisis in the basin, compromising broad conservation goals and social development in the long term. Better policies will require thought and planning to minimize growing threats and ensure the basin's sustainability for future generations.
To determine the effect of rivers, environmental conditions, and isolation by distance on the dis... more To determine the effect of rivers, environmental conditions, and isolation by distance on the distribution of species in Amazonia. Location: Brazilian Amazonia. Time period: Current. Major taxa studied: Birds, fishes, bats, ants, termites, butterflies, ferns + lycophytes, gingers and palms. We compiled a unique dataset of biotic and abiotic information from 822 plots spread over the Brazilian Amazon. We evaluated the effects of environment, geographic distance and dispersal barriers (rivers) on assemblage composition of animal and plant taxa using multivariate techniques and distance- and raw-data-based regression approaches. Environmental variables (soil/water), geographic distance, and rivers were associated with the distribution of most taxa. The wide and relatively old Amazon River tended to determine differences in community composition for most biological groups. Despite this association, environment and geographic distance were generally more important than rivers in explaini...
Aquatic Conservation: Marine and Freshwater Ecosystems, 2020
The extent and intensity of impacts of multiple new dams in the Amazon basin on specific biologic... more The extent and intensity of impacts of multiple new dams in the Amazon basin on specific biological groups are potentially large, but still uncertain and need to be better understood. It is known that river disruption and regulation by dams may affect sediment supplies, river channel migration, floodplain dynamics, and, as a major adverse consequence, are likely to decrease or even suppress ecological connectivity among populations of aquatic organisms and organisms dependent upon seasonally flooded environments. This article complements our previous results by assessing the relationships between dams, our Dam Environmental Vulnerability Index (DEVI), and the biotic environments threatened by the effects of dams. Because of the cartographic representation of DEVI, it is a useful tool to compare the potential hydrophysical impacts of proposed dams in the Amazon basin with the spatial distribution of biological diversity. As the impact of Amazonian dams on the biota of both rivers and...
Temperature-dependent sex determination occurs in many species of turtles. Because substrates dif... more Temperature-dependent sex determination occurs in many species of turtles. Because substrates differ in their heat retention capacities, a relatively small change in ambient temperature can exert great influence on sex ratios of hatchlings from clutches deposited in different substrates even within the same geographical area. Since Podocnemis unifilis is one of the Amazonian turtle species (Podocnemididae) with high behavioural plasticity in the use of nesting sites, we tested the influence of soil types on hatchling sex ratios in the Piagaçu Purus Sustainable Development Reserve along the lower Purus River, Brazil. During the 2013 and 2014 nesting seasons, we evaluated 26 nests on a sand bank (n = 14) and clay banks (n = 12). Approximately half of the hatchlings that emerged from each nest were sexed via gonad histological analysis (n = 341). We found a higher incidence of females in nests from the sandy substrate and more males in nests from the clayey substrate (χ2 = 40.466, df =...
Nesting site selection is of great ecological and evolutionary importance for turtles, because it... more Nesting site selection is of great ecological and evolutionary importance for turtles, because it is a key determinant of individual reproductive success. In this study we evaluated the effects of two types of nesting substrate (sand bank and clay banks) on the incubation success of a generalist nesting species, Podocnemis unifilis, in a floodplain area in the Brazilian Amazon. Nesting characteristics were recorded during the nesting seasons of 2012–2014, when 634 nests were monitored throughout the incubation period. Mean size of laying females did not vary between substrate types (sand = 24.71 cm; clay = 25.44 cm; P = 0.2054), nor was clutch size related to females’ sizes. However, females that nested on sand bank exhibited a clearer pattern of nest positioning relative to distances to vegetation and water line than those laying eggs on clay banks. Mean egg size (40.24 ± 2.68 mm) and weight (21.09 ± 5.46 g) did not vary between types of nesting substrate, and there was no variatio...
Revista da Sociedade Brasileira de Medicina Tropical, 2021
The type of catfish referred to as candirus, is a member of the Trichomycteridae and Cetopsidae f... more The type of catfish referred to as candirus, is a member of the Trichomycteridae and Cetopsidae families1,2. The subfamilies Vandelliinae and Stegophilinae (Trichomycteridae) and Cetopsinae (Cetopsidae) are relevant to human medicine, including forensics1,2,3,4. Herein, we present a brief essay on candirus and their relationship with human health and death. We examined published accounts and used our personal observations on the subject.
Rapids and waterfalls, and their associated fauna and flora are in peril. With the construction o... more Rapids and waterfalls, and their associated fauna and flora are in peril. With the construction of each new hydroelectric dam, more rapids and waterfalls are destroyed, leading to the disappearance of associated fauna and flora. Areas of rapids harbor distinct, highly endemic rheophilic fauna and flora adapted to an extreme environment. Rheophilic habitats also have disjunct distribution both within and across rivers. Rheophilic habitats thus represent islands of suitable habitat separated by stretches of unsuitable habitat. In this study, we investigated to what extent, if any, species of cichlid and anostomid fishes associated with rheophilic habitats were structured among the rapids of Araguaia River in the Brazilian Amazon. We tested both for population structuring as well as non-random distribution of lineages among rapids. Eight of the nine species had multiple lineages, five of these nine species were structured, and three of the eight species with multiple lineages showed non-random distribution of lineages among rapids. These results demonstrate that in addition to high levels of endemicism of rheophilic fishes, different rapids even within the same river are occupied by different lineages. Rheophilic species and communities occupying different rapids are, therefore, not interchangeable, and this realization must be taken into account when proposing mitigatory/compensatory measures in hydroelectric projects, and in conservation planning.
The ichthyofauna of the headwaters of the main tributaries of the mighty Solimões/Amazonas River ... more The ichthyofauna of the headwaters of the main tributaries of the mighty Solimões/Amazonas River has been little studied. Considering the importance of those environments for the overall fish diversity in that river system, we surveyed the composition of the fish fauna of the upper portion of Purus River and two of its tributaries (Caeté and Macapá rivers), state of Acre, Brazil. The collections were done in November 2004, using a seine net and a set of gillnets of different mesh sizes. A total of 735 specimens belonging to 86 species and 28 families were collected. Eight species, Creagrutus occidaneus, Phenacogaster pectinatus, Prionobrama filigera, Moenkhausia cf. lepidura, Leptagoniates pi (Characidade), Henonemus punctatus (Trichomycteridae), Toracocharax stellatus (Gateropelecidae), and Eigenmannia macrops (Sternopygidae) composed nearly half of the specimens collected. This survey adds 48 new records to the ichthyofauna of Purus River and elevates to 243 the number of...
Potamotrygonid stingrays are restricted to Neotropical rivers and information on their diet remai... more Potamotrygonid stingrays are restricted to Neotropical rivers and information on their diet remains scarce. Thus, the prey composition of four freshwater stingray species from the middle Negro River was studied using stomach contents analysis: Potamotrygon motoro (n=40), Potamotrygon orbignyi (n=27), Potamotrygon sp. "cururu" (n=26), and Paratrygon aiereba (n=34). Prey items were identified up to the lowest taxonomic level possible and analyzed with the Index of Relative Importance (%IRI). Teleosteans, crustaceans and insect larvae were consumed by all species in distinct proportions. Potamotrygon motoro fed mainly on palaemonid shrimps (33.8%) and trichodactylid crabs (48.7%). Stomach contents of Potamotrygon orbignyi were composed principally by insects (96.4%), with predominance of gomphid dragonfly larvae. Potamotrygon sp. "cururu" fed on crustaceans (shrimps and crabs: 49.4%) and insect larvae (30.2%). Paratrygon aiereba consumed mainly teleosteans (94.8%), ...
Contrasting with most sharks, which mainly use axial and caudal fin movements during locomotion, ... more Contrasting with most sharks, which mainly use axial and caudal fin movements during locomotion, batoids tend to use undulation or oscillation of the pectoral fins as their primarily locomotory mode. Movements by undulation are prevalent in many batoid groups, such as dasyatid and rajid species, whereas oscillatory movements are predominant among more derived stingrays (Rhinopteridae and Mobulidae) (ROSENBERGER & WESTNEAT 1999, ROSENBERGER 2001). Even though the role of the pectoral fins during swimming is well documented in batoids, the specific role of the pelvic fins in the locomotion of many species is unknown. However, they are known to play an important role in swimming and body maneuvering in batoids, especially during benthic locomotion (
Submetido em 22/11/2010 Aceito para publicação em 05/05/2011 Resumo O presente trabalho estudou c... more Submetido em 22/11/2010 Aceito para publicação em 05/05/2011 Resumo O presente trabalho estudou composição e abundância de peixes que realizam movimentos entre os bancos
Due to the existence of terrestrial barriers to freshwater fish dispersion, it is believed that i... more Due to the existence of terrestrial barriers to freshwater fish dispersion, it is believed that its distribution is strongly associated with historical factors related to the formation of the habitats they occupy. By the other hand, some studies reveal the influence of abiotic conditions (such as size of water bodies, pH, conductivity) on the composition of fish fauna occurring in small streams. This study aimed to investigate whether drainage basins, because catchment boundaries are potential barriers to fish dispersion, or the physical structure and physico-chemical characteristics of water have a greater influence on fish community structure in small streams. We sampled 22 streams belonging to five drainage basins in the Madeira-Purus interfluve. Fish were caught with dip nets and a small trawl, and data were simultaneously obtained on structural characteristics of the streams and physico-chemical characteristics of the water. Community composition was analyzed using Non-Metric M...
Biodiversity loss is one of the main challenges of our time and attempts to address it require a ... more Biodiversity loss is one of the main challenges of our time and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost.
ABSTRACTAimCommunity phylogenetics provides important information about the evolutionary and ecol... more ABSTRACTAimCommunity phylogenetics provides important information about the evolutionary and ecological factors help structure regional species assemblages. Here, we analyze phylogenetic diversity (phylodiversity) patterns among fish species in 97 sub-drainages of the Amazon basin, to evaluate the roles of historical and contemporary processes in generating and maintaining the exceptional richness and endemism of Amazonian fish species assemblages.LocationAmazon River basinTaxonFreshwater fishesMethodsUsing a large comprehensive database of freshwater fish species distributions, and a well-sampled molecular phylogeny of ray-finned (actinopterygian) fishes, we develop of multivariate statistical model to correlate estimated historical and contemporary environmental parameters with sub-drainage phylodiversity patterns. The model employs three phylogenetic metrics: i.e.: phylogenetic diversity (PD) sensu stricto, mean pairwise phylogenetic distance (MPD) between species capturing phylo...
Acanthodoras is the only genus of catfish known to secrete a conspicuous and abundant milky-looki... more Acanthodoras is the only genus of catfish known to secrete a conspicuous and abundant milky-looking substance through an axillary pore located just below the base of the posterior cleithral process. Despite this remarkable feature, there is no published information on the anatomical structures that produce the secretion and its possible biological/ecological functions. Dissection and histological analysis of preserved specimens of A. spinosissimus revealed the presence of a saccular axillary gland with large, binuclear secretory cells, similar to those found in other poisonous catfish. Secretory cells near the lumen appear to lose nuclei and become filled with secretory products, possibly with proteinaceous elements, as indicated by their eosinophilic appearance. As far as we know, the saccular morphology of the gland appears to constitute a unique characteristic of Acanthodoras among Doradidae catfishes. Further studies are necessary to determine the chemical composition of the sec...
Ichthyological surveys have traditionally been conducted using whole-specimen, capture-based samp... more Ichthyological surveys have traditionally been conducted using whole-specimen, capture-based sampling with varied but conventional fishing gear. Recently, environmental DNA (eDNA) metabarcoding has emerged as a complementary, and possible alternative, approach to whole-specimen methodologies. In the tropics, where much of the diversity remains undescribed, vast reaches continue unexplored, and anthropogenic activities are constant threats; there have been few eDNA attempts for ichthyological inventories. We tested the discriminatory power of eDNA using MiFish primers with existing public reference libraries and compared this with capture-based methods in two distinct ecosystems in the megadiverse Amazon basin. In our study, eDNA provided an accurate snapshot of the fishes at higher taxonomic levels and corroborated its effectiveness to detect specialized fish assemblages. Some flaws in fish metabarcoding studies are routine issues addressed in natural history museums. Thus, by expan...
Non-native fish (NNF) can threaten megadiverse aquatic ecosystems throughout the planet, but limi... more Non-native fish (NNF) can threaten megadiverse aquatic ecosystems throughout the planet, but limited information is available for the Amazon Region. In this study we review NNF data in the Amazonian macroregion using spatiotemporal records on the occurrence and the richness of NNF from a collaborative network of 35 regional experts, establishing the Amazon NNF database (ANNF). The NNF species richness was analyzed by river basin and by country, as well as the policies for each geopolitical division for the Amazon. The analysis included six countries (Brazil, Peru, Bolivia, Ecuador, Venezuela, and Colombia), together comprising more than 80% of the Amazon Region. A total of 1314 NNF occurrence records were gathered. The first record of NNF in this region was in 1939 and there has been a marked increase in the last 20 years (2000–2020), during which 75% of the records were observed. The highest number of localities with NNF occurrence records was observed for Colombia, followed by Bra...
The Tocantins-Araguaia Basin is one of the largest river systems in South America, located entire... more The Tocantins-Araguaia Basin is one of the largest river systems in South America, located entirely within Brazilian territory. In the last decades, capital-concentrating activities such as agribusiness, mining, and hydropower promoted extensive changes in land cover, hydrology, and environmental conditions. These changes are jeopardizing the basin's biodiversity and ecosystem services. Threats are escalating as poor environmental policies continue to be formulated, such as environmentally unsustainable hydropower plants, large-scale agriculture for commodity production, and aquaculture with non-native fish. If the current model persists, it will deepen the environmental crisis in the basin, compromising broad conservation goals and social development in the long term. Better policies will require thought and planning to minimize growing threats and ensure the basin's sustainability for future generations.
To determine the effect of rivers, environmental conditions, and isolation by distance on the dis... more To determine the effect of rivers, environmental conditions, and isolation by distance on the distribution of species in Amazonia. Location: Brazilian Amazonia. Time period: Current. Major taxa studied: Birds, fishes, bats, ants, termites, butterflies, ferns + lycophytes, gingers and palms. We compiled a unique dataset of biotic and abiotic information from 822 plots spread over the Brazilian Amazon. We evaluated the effects of environment, geographic distance and dispersal barriers (rivers) on assemblage composition of animal and plant taxa using multivariate techniques and distance- and raw-data-based regression approaches. Environmental variables (soil/water), geographic distance, and rivers were associated with the distribution of most taxa. The wide and relatively old Amazon River tended to determine differences in community composition for most biological groups. Despite this association, environment and geographic distance were generally more important than rivers in explaini...
Aquatic Conservation: Marine and Freshwater Ecosystems, 2020
The extent and intensity of impacts of multiple new dams in the Amazon basin on specific biologic... more The extent and intensity of impacts of multiple new dams in the Amazon basin on specific biological groups are potentially large, but still uncertain and need to be better understood. It is known that river disruption and regulation by dams may affect sediment supplies, river channel migration, floodplain dynamics, and, as a major adverse consequence, are likely to decrease or even suppress ecological connectivity among populations of aquatic organisms and organisms dependent upon seasonally flooded environments. This article complements our previous results by assessing the relationships between dams, our Dam Environmental Vulnerability Index (DEVI), and the biotic environments threatened by the effects of dams. Because of the cartographic representation of DEVI, it is a useful tool to compare the potential hydrophysical impacts of proposed dams in the Amazon basin with the spatial distribution of biological diversity. As the impact of Amazonian dams on the biota of both rivers and...
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