Knodus borari, a new species from the lower Rio Tapajós basin (Characiformes: Characidae).

A new species of Knodus from the Rio Cupari, a right-bank tributary of the lower Rio Tapajós, is described. Among its congeners, the new species shares exclusively with K. figueiredoi the presence of only uni-tricuspid teeth in the premaxilla, maxilla and dentary. Knodus borari differs from K. figueiredoi by the colour pattern and morphological characteristics. The new species is the fifth species of the genus described from the Rio Tapajós basin, and the second restricted to the lower portion of the basin. This is additional evidence that the lower Rio Tapajós basin is a region of ichthyofaunal endemism.

Distribution of goblet and endocrine cells in the intestine: A comparative study in Amazonian freshwater Tambaqui and hybrid catfish.

Goblet cells (GCs) and endocrine cells (ECs) play an important role in intestine physiology, and few studies currently exist for Amazonian fishes. This study aimed to quantify the distribution of GCs and ECs producing cholecystokinin-8 and neuropeptide Y, assessed by mucin histochemistry and peptides immunohistochemistry, in the intestine of two Amazonian species with different feeding habits Tambaqui (Colossosoma macropomum) and hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus), an omnivore and carnivore, respectively. A systematic literature review correlating feeding habit and GC and EC distribution was also included to contribute to the comparative study. The results of this study provided novel information about the gut cells of Tambaqui and hybrid catfish. Both, GCs and ECs can be found sweeping the entire intestine of Tambaqui and hybrid catfish although the cells can be more concentrated in certain segments. The GCs and ECs in Tambaqui were more uniformly distributed in the midgut segments (T1, T2, and T3). Unlike, in hybrid catfish GCs were more concentrated in the hindgut (C4) and ECs mainly in the two midgut segments (C1 and C2) of hybrid catfish. Based on the comparison between Tambaqui, hybrid catfish, and other fishes in the literature review, we suggest that cell distribution can be partially explained by feeding habits, carnivorous vs. omnivorous.

Efeito das modificações ambientais naturais e antropicas na reprodução de peixes amazônicos / Effect of natural and anthropogenic changes in Amazonian fish reproduction

Alterações de táticas reprodutivas em peixes podem ser provocadas por vários fatores como as mudanças ambientais naturais ou aquelas provocadas pela construção de grandes empreendimentos como o caso de hidrelétricas. Para verificar como as condições ambientais impostas influenciam na reprodução dos peixes, parâmetros reprodutivos populacionais como tamanho médio de primeira maturação sexual (L50), menor fêmea madura capturada, tamanho máximo da fêmea (L∞), tamanho relativo da primeira maturação (L50/L∞) e intensidade reprodutiva (IR), foram determinados para assembleias de peixes de uma área não impactada de várzea e da UHE Balbina. Os resultados mostraram um padrão sazonal de reprodução durante a enchente, indicando a importância da sequência seca/enchente/cheia para o sucesso reprodutivo das espécies em ambientes de várzea e da precipitação para as espécies em reservatório. Ainda, foi observado mudança na intensidade reprodutiva da assembleia nas duas situações e nas táticas reprodutivas das espécies do reservatório. Eventos climáticos drásticos podem influenciar a atividade reprodutiva, o recrutamento e consequentemente a manutenção dos estoques pesqueiros, assim como a interrupção do curso natural de um rio pode provocar mudanças nas táticas reprodutivas de espécies como mecanismo adaptativo ao novo ambiente.

Changes in reproductive tactics in fishes can be caused by several factors such as natural climate changes or those caused by the construction of large projects as it is the case of hydroelectric plants. In order to evaluate environmental conditions on fish reproduction, a few reproductive parameters such as size at first maturation (L50), smallest ripe female captured, maximum female size (L∞), relative size at first maturation (L50/L∞) and reproductive intensity (IR) were determined for fish assemblages in a non impacted floodplain area and in a neotropical reservoir, Balbina hydroelectric plant. The results showed a seasonal pattern of fish reproduction during the rising of the water and indicate the importance of the flood pulse to the reproductive success of species in the floodplain as well as precipitation for the species in the reservoir. Still, changes in the reproductive intensity in both sites and in the reproductive parameters of the reservoir fishes could be observed. Drastic climate events may influence the reproductive activity, recruitment, and consequently the maintenance of fish stocks, as well as the interruption of the natural course of a river can cause changes in the reproduction of species as an adaptive mechanism to the new environment formed.

Efeito das modificações ambientais naturais e antropicas na reprodução de peixes amazônicos / Effect of natural and anthropogenic changes in Amazonian fish reproduction

Alterações de táticas reprodutivas em peixes podem ser provocadas por vários fatores como as mudanças ambientais naturais ou aquelas provocadas pela construção de grandes empreendimentos como o caso de hidrelétricas. Para verificar como as condições ambientais impostas influenciam na reprodução dos peixes, parâmetros reprodutivos populacionais como tamanho médio de primeira maturação sexual (L50), menor fêmea madura capturada, tamanho máximo da fêmea (L∞), tamanho relativo da primeira maturação (L50/L∞) e intensidade reprodutiva (IR), foram determinados para assembleias de peixes de uma área não impactada de várzea e da UHE Balbina. Os resultados mostraram um padrão sazonal de reprodução durante a enchente, indicando a importância da sequência seca/enchente/cheia para o sucesso reprodutivo das espécies em ambientes de várzea e da precipitação para as espécies em reservatório. Ainda, foi observado mudança na intensidade reprodutiva da assembleia nas duas situações e nas táticas reprodutivas das espécies do reservatório. Eventos climáticos drásticos podem influenciar a atividade reprodutiva, o recrutamento e consequentemente a manutenção dos estoques pesqueiros, assim como a interrupção do curso natural de um rio pode provocar mudanças nas táticas reprodutivas de espécies como mecanismo adaptativo ao novo ambiente.(AU)

Changes in reproductive tactics in fishes can be caused by several factors such as natural climate changes or those caused by the construction of large projects as it is the case of hydroelectric plants. In order to evaluate environmental conditions on fish reproduction, a few reproductive parameters such as size at first maturation (L50), smallest ripe female captured, maximum female size (L∞), relative size at first maturation (L50/L∞) and reproductive intensity (IR) were determined for fish assemblages in a non impacted floodplain area and in a neotropical reservoir, Balbina hydroelectric plant. The results showed a seasonal pattern of fish reproduction during the rising of the water and indicate the importance of the flood pulse to the reproductive success of species in the floodplain as well as precipitation for the species in the reservoir. Still, changes in the reproductive intensity in both sites and in the reproductive parameters of the reservoir fishes could be observed. Drastic climate events may influence the reproductive activity, recruitment, and consequently the maintenance of fish stocks, as well as the interruption of the natural course of a river can cause changes in the reproduction of species as an adaptive mechanism to the new environment formed.(AU)

Diversidad de peces en la cuenca del Alto Yuruá (Ucayali, Perú)

El presente estudio compara los patrones de diversidad de peces en la Cuenca del Alto Yurúa. El área de estudio comprendió tres sub cuencas: Beu, Breu y Yurúa, todas sin impacto antropogénico. Mediante pesca con redes de arrastre a orilla, se colectaron 10564 individuos y se identificaron 185 especies de peces. En escala regional, el promedio del índice de diversidad Shannon (H') para Beu fue de 2,02; para Breu 1,84 y para Yuruá 1,75. Según el análisis de rarefacción, Yurúa tuvo la riqueza de especies esperada más alta (91 spp.) en comparación con Beu (87) y Breu (68). En la escala local, los ambientes lóticos presentaron mayor riqueza y diversidad que los lénticos. La diversidad promedio (H') fue mayor en lóticos (Beu 2,04; Breu 1,90; y Yurúa 1,86), comparados con lénticos de los mismos (Beu 1,66; Breu 1,86; y Yurúa 1,82). La mayor diversidad de peces observada en ambiente lóticos podría explicarse por que la mayoría de peces amazónicos tienen el comportamiento de desplazarse por los canales principales de los ríos, mientras que los lagos pueden presentar condiciones de estrés estacional (alta presión de depredación y bajas concentraciones de oxígeno disuelto).

The present study compares the patterns of fish's diversity of the Alto Yurúa Basin. The study area included three sub basins: Beu, Breu and Yurúa, all without anthropogenic impact. Fishing was carried out with trawls, 10564 individuals were collected and 185 fish's species were identified. In regional scale, the average of the Shannon diversity index (H') for Beu was of 2,02; for Breu 1,84 and Yuruá 1,75. The rarefaction analysis shows to Yurúa with the highest species richness (91 spp.), in comparison with Beu (87) and Breu (68). In the local scale, the diversity average (H') was highest in lotic environments (Beu 2,04; Breu 1,90; and Yurúa 1,86), compared with respective lentics environments (Beu 1,66; Breu 1,86; and Yurúa 1,82). The highest diversity of fishes observed in lotic environments could be explained because the most of Amazonian fishes have the behavior to travel by the main channels of the rivers, while the lakes can have stress seasonal conditions (high depredation pressure and low concentrations of dissolved oxygen).