RESUMEN

The environmental impacts caused by fish farming can lead to changes in aquatic ecosystems, especially in fish communities. In this study, we investigated possible changes in water quality, in the number of species and individuals of the same species caused by the construction of fish nurseries in dammed Amazonian streams. For this purpose, four streams located in the municipalities of Novo Airão and Presidente Figueiredo were selected. Samples were collected in streams without fish farming and in streams with stretches used for fish farming, where collections took place both downstream and upstream. The fish were captured, identified, quantified and the water was collected for physical and chemical analyses, in addition to the environmental characterization that was carried out. Comparisons were made using fish richness and abundance indices between the sampled points and correspondence analysis of the species identified at the collection sites, using the Mantel test and principal component analysis (PCA) for the environmental characteristics of the water and variables physical and chemical, and permutational multivariate analysis of variance (PERMANOVA) to verify the possible effects of species composition on the sampled conditions and on the analyzed environmental variables. In total, 2,302 fish belonging to 53 species, 15 families and six orders were found. We conclude that the Amazonian streams dammed for fish farming, under the analyzed conditions, can be characterized as environments with different and specific levels of richness and abundance, however, the data set analyzed in this study did not show that these characteristics are directly related to productive activity. We recommend that further studies be carried out following the current research.

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The present study objectified to evaluate the trophic relationships and the possible aggressive mimicry involving Carnegiella strigata, Carnegiella marthae and Gnathocharax steindachneri, in lowland forest streams. Samplings occurred in November 2002, March and August 2003 in Amanã Sustainable Development Reserve (ASDR). The total of 943 fish was caught, being 79.43% of C. marthae, 3.18% of C. strigata and 17.39% of G. steindachneri. Stomach contents, degree of stomach repletion, relative volume and frequency of occurrence of food items were evaluated. Thirteen food items were identified, and the presence of terrestrial and aquatic insects indicates the high dependence of these species and the flooded forest. Low feeding overlap was observed between Carnegiella strigata and C. marthae compared to Gnathocharax steindachneri. However, the overlap between the two Carnegiella species was relatively high, which could explain the low frequency of syntopic occurrence among these species, suggesting a possible case of competitive exclusion.(AU)

Este estudo teve como objetivo analisar as relações tróficas e a possível existência de uma relação de mimetismo agressivo envolvendo Carnegiella strigata, Carnegiella marthae e Gnathocharax steindachneri, em igarapés de terra firme. As coletas ocorreram em novembro de 2002, março e agosto de 2003 e foram realizadas na Reserva de Desenvolvimento Sustentável de Amanã (RDSA). Foram capturados 943 peixes, onde C. marthae representou 79,43%, C. strigata 3,18% e G. steindachneri 17,39%. Foram analisados os conteúdos estomacais e verificados grau de repleção, volume relativo e frequência de ocorrência dos alimentos. Foram identificados 13 itens alimentares, onde insetos terrestres e aquáticos denotaram alto grau de dependência destas espécies em relação à floresta alagada. Ocorreu baixa sobreposição alimentar das espécies Carnegiella strigata e C. marthae em relação a Gnathocharax steindachneri. Entretanto, a sobreposição entre as duas espécies de Carnegiella foi relativamente alta, o que poderia explicar a baixa frequência de ocorrência sintópica entre essas espécies, sugerindo um possível caso de exclusão competitiva.(AU)

Asunto(s)

RESUMEN

The present study objectified to evaluate the trophic relationships and the possible aggressive mimicry involving Carnegiella strigata, Carnegiella marthae and Gnathocharax steindachneri, in lowland forest streams. Samplings occurred in November 2002, March and August 2003 in Amanã Sustainable Development Reserve (ASDR). The total of 943 fish was caught, being 79.43% of C. marthae, 3.18% of C. strigata and 17.39% of G. steindachneri. Stomach contents, degree of stomach repletion, relative volume and frequency of occurrence of food items were evaluated. Thirteen food items were identified, and the presence of terrestrial and aquatic insects indicates the high dependence of these species and the flooded forest. Low feeding overlap was observed between Carnegiella strigata and C. marthae compared to Gnathocharax steindachneri. However, the overlap between the two Carnegiella species was relatively high, which could explain the low frequency of syntopic occurrence among these species, suggesting a possible case of competitive exclusion.

Este estudo teve como objetivo analisar as relações tróficas e a possível existência de uma relação de mimetismo agressivo envolvendo Carnegiella strigata, Carnegiella marthae e Gnathocharax steindachneri, em igarapés de terra firme. As coletas ocorreram em novembro de 2002, março e agosto de 2003 e foram realizadas na Reserva de Desenvolvimento Sustentável de Amanã (RDSA). Foram capturados 943 peixes, onde C. marthae representou 79,43%, C. strigata 3,18% e G. steindachneri 17,39%. Foram analisados os conteúdos estomacais e verificados grau de repleção, volume relativo e frequência de ocorrência dos alimentos. Foram identificados 13 itens alimentares, onde insetos terrestres e aquáticos denotaram alto grau de dependência destas espécies em relação à floresta alagada. Ocorreu baixa sobreposição alimentar das espécies Carnegiella strigata e C. marthae em relação a Gnathocharax steindachneri. Entretanto, a sobreposição entre as duas espécies de Carnegiella foi relativamente alta, o que poderia explicar a baixa frequência de ocorrência sintópica entre essas espécies, sugerindo um possível caso de exclusão competitiva.

Asunto(s)

RESUMEN

The present study objectified to evaluate the trophic relationships and the possible aggressive mimicry involving Carnegiella strigata, Carnegiella marthae and Gnathocharax steindachneri, in lowland forest streams. Samplings occurred in November 2002, March and August 2003 in Amanã Sustainable Development Reserve (ASDR). The total of 943 fish was caught, being 79.43% of C. marthae, 3.18% of C. strigata and 17.39% of G. steindachneri. Stomach contents, degree of stomach repletion, relative volume and frequency of occurrence of food items were evaluated. Thirteen food items were identified, and the presence of terrestrial and aquatic insects indicates the high dependence of these species and the flooded forest. Low feeding overlap was observed between Carnegiella strigata and C. marthae compared to Gnathocharax steindachneri. However, the overlap between the two Carnegiella species was relatively high, which could explain the low frequency of syntopic occurrence among these species, suggesting a possible case of competitive exclusion.

Este estudo teve como objetivo analisar as relações tróficas e a possível existência de uma relação de mimetismo agressivo envolvendo Carnegiella strigata, Carnegiella marthae e Gnathocharax steindachneri, em igarapés de terra firme. As coletas ocorreram em novembro de 2002, março e agosto de 2003 e foram realizadas na Reserva de Desenvolvimento Sustentável de Amanã (RDSA). Foram capturados 943 peixes, onde C. marthae representou 79,43%, C. strigata 3,18% e G. steindachneri 17,39%. Foram analisados os conteúdos estomacais e verificados grau de repleção, volume relativo e frequência de ocorrência dos alimentos. Foram identificados 13 itens alimentares, onde insetos terrestres e aquáticos denotaram alto grau de dependência destas espécies em relação à floresta alagada. Ocorreu baixa sobreposição alimentar das espécies Carnegiella strigata e C. marthae em relação a Gnathocharax steindachneri. Entretanto, a sobreposição entre as duas espécies de Carnegiella foi relativamente alta, o que poderia explicar a baixa frequência de ocorrência sintópica entre essas espécies, sugerindo um possível caso de exclusão competitiva.

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Abstract The present study objectified to evaluate the trophic relationships and the possible aggressive mimicry involving Carnegiella strigata, Carnegiella marthae and Gnathocharax steindachneri, in lowland forest streams. Samplings occurred in November 2002, March and August 2003 in Amanã Sustainable Development Reserve (ASDR). The total of 943 fish was caught, being 79.43% of C. marthae, 3.18% of C. strigata and 17.39% of G. steindachneri. Stomach contents, degree of stomach repletion, relative volume and frequency of occurrence of food items were evaluated. Thirteen food items were identified, and the presence of terrestrial and aquatic insects indicates the high dependence of these species and the flooded forest. Low feeding overlap was observed between Carnegiella strigata and C. marthae compared to Gnathocharax steindachneri. However, the overlap between the two Carnegiella species was relatively high, which could explain the low frequency of syntopic occurrence among these species, suggesting a possible case of competitive exclusion.

Resumo Este estudo teve como objetivo analisar as relações tróficas e a possível existência de uma relação de mimetismo agressivo envolvendo Carnegiella strigata, Carnegiella marthae e Gnathocharax steindachneri, em igarapés de terra firme. As coletas ocorreram em novembro de 2002, março e agosto de 2003 e foram realizadas na Reserva de Desenvolvimento Sustentável de Amanã (RDSA). Foram capturados 943 peixes, onde C. marthae representou 79,43%, C. strigata 3,18% e G. steindachneri 17,39%. Foram analisados os conteúdos estomacais e verificados grau de repleção, volume relativo e frequência de ocorrência dos alimentos. Foram identificados 13 itens alimentares, onde insetos terrestres e aquáticos denotaram alto grau de dependência destas espécies em relação à floresta alagada. Ocorreu baixa sobreposição alimentar das espécies Carnegiella strigata e C. marthae em relação a Gnathocharax steindachneri. Entretanto, a sobreposição entre as duas espécies de Carnegiella foi relativamente alta, o que poderia explicar a baixa frequência de ocorrência sintópica entre essas espécies, sugerindo um possível caso de exclusão competitiva.

RESUMEN

The present study objectified to evaluate the trophic relationships and the possible aggressive mimicry involving Carnegiella strigata, Carnegiella marthae and Gnathocharax steindachneri, in lowland forest streams. Samplings occurred in November 2002, March and August 2003 in Amanã Sustainable Development Reserve (ASDR). The total of 943 fish was caught, being 79.43% of C. marthae, 3.18% of C. strigata and 17.39% of G. steindachneri. Stomach contents, degree of stomach repletion, relative volume and frequency of occurrence of food items were evaluated. Thirteen food items were identified, and the presence of terrestrial and aquatic insects indicates the high dependence of these species and the flooded forest. Low feeding overlap was observed between Carnegiella strigata and C. marthae compared to Gnathocharax steindachneri. However, the overlap between the two Carnegiella species was relatively high, which could explain the low frequency of syntopic occurrence among these species, suggesting a possible case of competitive exclusion.

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

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

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

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

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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 Multidimensional Scaling (NMDS), and variables related to structural and physico-chemical characteristics were summarized by Principal Component Analysis (PCA). Two explanatory models relating faunal composition to environmental factors were constructed: the first using only continuous variables and the second including the drainage basin as a categorical variable. The Akaike Information Criterion (AIC) and AIC weight were used to select the best model. Although structural and physico-chemical variables significantly contributed to explaining faunal composition, the model including the drainage basin was clearly the better of the two models (more than 90% support in the data). The importance of drainage basins in structuring fish communities in streams may have significant consequences for conservation planning in these environments.

Asunto(s)

RESUMEN

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 Multidimensional Scaling (NMDS), and variables related to structural and physico-chemical characteristics were summarized by Principal Component Analysis (PCA). Two explanatory models relating faunal composition to environmental factors were constructed: the first using only continuous variables and the second including the drainage basin as a categorical variable. The Akaike Information Criterion (AIC) and AIC weight were used to select the best model. Although structural and physico-chemical variables significantly contributed to explaining faunal composition, the model including the drainage basin was clearly the better of the two models (more than 90% support in the data). The importance of drainage basins in structuring fish communities in streams may have significant consequences for conservation planning in these environments.

Devido à existência de barreiras terrestres à dispersão de peixes de água doce, acredita-se que sua distribuição é fortemente associada a fatores históricos relacionados à formação dos habitats que ocupam. Por outro lado, alguns estudos revelam a influência de condições abióticas (tais como o tamanho do corpo d'água, pH, condutividade) na composição da fauna ictiíca de rios de pequena ordem. Este trabalho teve como objetivo investigar se bacias hidrográficas, cujo divisor de águas representa uma potencial barreira para a dispersão dos peixes, ou a estrutura física e características físico-químicas da água têm maior efeito sobre a estrutura de comunidades de peixes de riachos de pequena ordem. Foram amostrados 22 riachos, pertencentes a cinco bacias hidrográficas no interflúvio Madeira-Purus. Os peixes foram capturados com puçás e uma pequena rede de arrasto, e simultaneamente foram obtidos dados sobre as características estruturais dos riachos e físico-químicas da água. A composição das comunidades foi analisada por meio de um Escalonamento Multidimensional Não-Métrico (NMDS) e as variáveis relacionadas às características estruturais e físico-químicas foram sintetizadas por meio de uma Análise de Componentes Principais (PCA). Dois modelos explicativos relacionando a composição da fauna aos fatores ambientais foram construídos: o primeiro utilizando apenas variáveis contínuas, e o segundo incluindo as bacias hidrográficas como variável categórica. O Critério de Informação de Akaike (AIC) e o peso do AIC foram utilizados para a seleção do melhor modelo. Apesar de variáveis físicas e físico-químicas terem contribuído significativamente para explicar a composição faunística, o modelo incluindo bacias hidrográficas foi claramente superior (mais de 90% de suporte nos dados). A importância de bacias de drenagem para a estruturação da comunidade de peixes de riachos pode ter consequências relevantes para o planejamento para a conservação desses ambientes.

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RESUMEN

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 Multidimensional Scaling (NMDS), and variables related to structural and physico-chemical characteristics were summarized by Principal Component Analysis (PCA). Two explanatory models relating faunal composition to environmental factors were constructed: the first using only continuous variables and the second including the drainage basin as a categorical variable. The Akaike Information Criterion (AIC) and AIC weight were used to select the best model. Although structural and physico-chemical variables significantly contributed to explaining faunal composition, the model including the drainage basin was clearly the better of the two models (more than 90% support in the data). The importance of drainage basins in structuring fish communities in streams may have significant consequences for conservation planning in these environments.(AU)

Devido à existência de barreiras terrestres à dispersão de peixes de água doce, acredita-se que sua distribuição é fortemente associada a fatores históricos relacionados à formação dos habitats que ocupam. Por outro lado, alguns estudos revelam a influência de condições abióticas (tais como o tamanho do corpo d'água, pH, condutividade) na composição da fauna ictiíca de rios de pequena ordem. Este trabalho teve como objetivo investigar se bacias hidrográficas, cujo divisor de águas representa uma potencial barreira para a dispersão dos peixes, ou a estrutura física e características físico-químicas da água têm maior efeito sobre a estrutura de comunidades de peixes de riachos de pequena ordem. Foram amostrados 22 riachos, pertencentes a cinco bacias hidrográficas no interflúvio Madeira-Purus. Os peixes foram capturados com puçás e uma pequena rede de arrasto, e simultaneamente foram obtidos dados sobre as características estruturais dos riachos e físico-químicas da água. A composição das comunidades foi analisada por meio de um Escalonamento Multidimensional Não-Métrico (NMDS) e as variáveis relacionadas às características estruturais e físico-químicas foram sintetizadas por meio de uma Análise de Componentes Principais (PCA). Dois modelos explicativos relacionando a composição da fauna aos fatores ambientais foram construídos: o primeiro utilizando apenas variáveis contínuas, e o segundo incluindo as bacias hidrográficas como variável categórica. O Critério de Informação de Akaike (AIC) e o peso do AIC foram utilizados para a seleção do melhor modelo. Apesar de variáveis físicas e físico-químicas terem contribuído significativamente para explicar a composição faunística, o modelo incluindo bacias hidrográficas foi claramente superior (mais de 90% de suporte nos dados). A importância de bacias de drenagem para a estruturação da comunidade de peixes de riachos pode ter consequências relevantes para o planejamento para a conservação desses ambientes.(AU)

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Synbranchidae belongs to the Synbranchiformes and occurs in Africa, Asia, Australia, Mexico, and Central and South America. This family comprises four genera: Synbranchus, Ophisternon, Monopterus, and Macrotrema. Only two are known from the neotropical region, Ophisternon and Synbranchus. According to current classification, Synbranchus has three valid species: S. marmoratus (Bloch 1795), S. madeirae (Rosen and Rumney 1972), and S. lampreia (Favorito, Zanata and Assumpção 2005). Thus the present research is aimed to cytogenetically characterize (by classical and molecular methods) two syntopic species-S. aff. lampreia and S. madeirae-from the central Amazon basin to validate the taxonomy of both species and provide a revisionary discussion on the cytogenetics of Synbranchiformes. Synbranchus aff. lampreia was found to possess 2n = 44 chromosomes (6 m + 2st + 36a, NF = 50), while S. madeirae had 2n = 46 chromosomes (6 m + 2st + 38a, NF = 52). Constitutive heterochromatin was dominant in the centromeric and terminal regions of most of the chromosomes in both species, although the precise distribution patterns were species-specific. The nucleolar organizing region was single in S. aff. lampreia and multiple in S. madeirae, as indicated by both AgNO(3) and hybridization using 18S rDNA probes. The 5S rDNA sites were located interstitially on the long arms of an acrocentric pair in both species, and the telomeric probe did not show any interstitial sites in either species. These data indicate the occurrence of interspecific karyotypic variability in Synbranchus and suggest that taxonomic review for this genus is necessary.

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The influence of fatty acid composition of the diets on the productive performance and on cold and heat tolerance of juvenile freshwater angelfish (Pterophyllum scalare), in three different phases, was studied. Phase I studied the productive performance of freshwater angelfish in a completely randomized experimental design with four treatments, canola, linseed, olive and soybean oils and four replicates during 50 days using 192 fish in 16 aquaria. Phase II studied the cold tolerance of juvenile freshwater angelfish using 72 juvenile freshwater angelfish, coming from phase I and maintained in 12 aquaria climatized chamber. The temperature was reduced 1ºC per day, until the observation of 100 percent fish mortality. Phase III, it was studied the heat tolerance of juvenile freshwater angelfish employing an identical procedure to phase II, but with a daily increase of 1ºC. Significant differences (P>0.05) were not observed for any parameters evaluated. Thus, it was concluded that the type of vegetable oil (canola, linseed, olive and soybean) used as a diet supplement did not affect the productive performance, nor the tolerance to cold and heat, of juvenile freshwater angelfish.

Avaliou-se a influência da suplementação de lipídeos na dieta, com diferentes composições de ácidos graxos, sobre o desempenho produtivo e tolerância ao frio e ao calor de juvenis de acará-bandeira (Pterophyllum scalare). O experimento foi realizado em três fases. Na fase um avaliou-se o desempenho produtivo dos peixes em delineamento inteiramente ao acaso com quatro tratamentos - óleos de canola, linhaça, oliva e soja - e quatro repetições, durante 50 dias usando 192 peixes distribuídos em 16 aquários. Na segunda fase, avaliou-se a tolerância ao frio, usando 72 peixes, procedentes da fase um, distribuídos em 12 aquários e mantidos em câmara climatizada. A temperatura foi reduzida de 1ºC por dia até a observação de 100 por cento de mortalidade dos peixes. Na fase três, avaliou-se a tolerância ao calor com procedimentos semelhantes aos da fase dois, porém a temperatura foi elevada 1ºC por dia. Não foram observadas diferenças significativas (P>0,05) para os parâmetros avaliados. Conclui-se que a suplementação de óleos vegetais nas dietas não inferiu no desempenho produtivo e na tolerância ao frio e ao calor de juvenis de acará-bandeira.

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RESUMEN

The influence of fatty acid composition of the diets on the productive performance and on cold and heat tolerance of juvenile freshwater angelfish (Pterophyllum scalare), in three different phases, was studied. Phase I studied the productive performance of freshwater angelfish in a completely randomized experimental design with four treatments, canola, linseed, olive and soybean oils and four replicates during 50 days using 192 fish in 16 aquaria. Phase II studied the cold tolerance of juvenile freshwater angelfish using 72 juvenile freshwater angelfish, coming from phase I and maintained in 12 aquaria climatized chamber. The temperature was reduced 1ºC per day, until the observation of 100 percent fish mortality. Phase III, it was studied the heat tolerance of juvenile freshwater angelfish employing an identical procedure to phase II, but with a daily increase of 1ºC. Significant differences (P>0.05) were not observed for any parameters evaluated. Thus, it was concluded that the type of vegetable oil (canola, linseed, olive and soybean) used as a diet supplement did not affect the productive performance, nor the tolerance to cold and heat, of juvenile freshwater angelfish.(AU)

Avaliou-se a influência da suplementação de lipídeos na dieta, com diferentes composições de ácidos graxos, sobre o desempenho produtivo e tolerância ao frio e ao calor de juvenis de acará-bandeira (Pterophyllum scalare). O experimento foi realizado em três fases. Na fase um avaliou-se o desempenho produtivo dos peixes em delineamento inteiramente ao acaso com quatro tratamentos - óleos de canola, linhaça, oliva e soja - e quatro repetições, durante 50 dias usando 192 peixes distribuídos em 16 aquários. Na segunda fase, avaliou-se a tolerância ao frio, usando 72 peixes, procedentes da fase um, distribuídos em 12 aquários e mantidos em câmara climatizada. A temperatura foi reduzida de 1ºC por dia até a observação de 100 por cento de mortalidade dos peixes. Na fase três, avaliou-se a tolerância ao calor com procedimentos semelhantes aos da fase dois, porém a temperatura foi elevada 1ºC por dia. Não foram observadas diferenças significativas (P>0,05) para os parâmetros avaliados. Conclui-se que a suplementação de óleos vegetais nas dietas não inferiu no desempenho produtivo e na tolerância ao frio e ao calor de juvenis de acará-bandeira.(AU)

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RESUMEN

Ancistrus is the most speciose genus of the tribe Ancistrini, with 58 valid species and many yet to be described. Cytogenetic studies were conducted on five apparently undescribed species from the Amazon basin, which showed different diploid numbers: Ancistrus sp. Purus (2n = 34); Ancistrus sp. Macoari (2n = 46); Ancistrus sp. Dimona (2n = 52); Ancistrus sp. Vermelho (2n = 42) and Ancistrus sp. Trombetas (2n = 38). All species possessed only one pair of NOR-carrying chromosomes, but with extensive variation in both the location on the chromosome as well as in the position of the ribosomal sites on the karyotype. The karyotypic evolution of Ancistrus species seems to be based on chromosomal rearrangements, with a tendency to a reduction of the diploid number. Two new instances of XX/XY sex chromosomes for Ancistrus species, based on the heteromorphism in the male karyotype, were also recorded. The large karyotypic diversity among Ancistrus species may be related to biological and behavioural characteristics of these fish that include microhabitat preferences, territoriality and specialized reproductive tactics. These characteristics may lead to a fast rate of fixation of chromosomal mutations and eventually speciation across the basin.

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RESUMEN

Several groups of Amazonian fishes exhibit behavioral, morphological and physiological characteristics that allow occupying hypoxic environments, despite the energetic costs of living in such harsh conditions. One of the supposed advantages of occupying hypoxic habitats would be a lower predation pressure resulting from a lower number of piscivorous fishes in those environments. We tested this hypothesis in an area of the Amazon River floodplain through gill net fishing in normoxic and hypoxic habitats. From the 103 species caught, 38 were classified as piscivores. We found no difference in the number of piscivorous species captured in hypoxic and normoxic habitats (chi2 = 0.23; p = 0.63; df = 1) but piscivorous individuals were more numerous in normoxic than in hypoxic sampling stations (chi2 = 104.4; p < 0.001; df = 1). This indicates that environments submitted to low oxygen conditions may in fact function as refuges against piscivorous fishes in the Amazonian floodplains.

Asunto(s)

RESUMEN

Several groups of Amazonian fishes exhibit behavioral, morphological and physiological characteristics that allow occupying hypoxic environments, despite the energetic costs of living in such harsh conditions. One of the supposed advantages of occupying hypoxic habitats would be a lower predation pressure resulting from a lower number of piscivorous fishes in those environments. We tested this hypothesis in an area of the Amazon River floodplain through gill net fishing in normoxic and hypoxic habitats. From the 103 species caught, 38 were classified as piscivores. We found no difference in the number of piscivorous species captured in hypoxic and normoxic habitats (chi2 = 0.23; p = 0.63; df = 1) but piscivorous individuals were more numerous in normoxic than in hypoxic sampling stations (chi2 = 104.4; p < 0.001; df = 1). This indicates that environments submitted to low oxygen conditions may in fact function as refuges against piscivorous fishes in the Amazonian floodplains.

Diversos grupos de peixes amazônicos apresentam mecanismos para suportar condições de hipóxia, incluindo especializações comportamentais, morfológicas e fisiológicas, apesar do custo energético envolvido. Uma das supostas vantagens em ocupar ambientes hipóxicos seria a redução da pressão de predação, devido à presença de um menor número de peixes piscívoros. Testamos esta hipótese em um ambiente de várzea do rio Amazonas, por meio de coleta de peixes com malhadeiras em ambientes hipóxicos e normóxicos. Das 103 espécies capturadas, 38 foram classificadas como piscívoras. Não houve diferença no número de espécies piscívoras e não piscívoras nos dois tipos de ambientes amostrados (chi2 = 0,23; p = 0,63; gl = 1), mas a proporção de peixes piscívoros foi maior sob condições de normóxia (chi2 = 104,40; p < 0,001; gl = 1). Isto indica que ambientes com baixa concentração de oxigênio dissolvido podem de fato funcionar como locais de refúgio contra peixes piscívoros nas várzeas amazônicas.

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