Luciano Fogaça de Assis Montag

Seasonal changes in the gonadossomatic index, allometric condition factor and sex ratio of an auchenipterid catfish from eastern Amazonia

The aim of the present study was to evaluate the seasonal pattern of the gonadosomatic index (GSI), condition factor (K), and sex ratio in the catfish Auchenipterichthys longimanus (Siluriformes: Auchenipteridae) as an approach to identify its reproductive period. A total of 589 A. longimanus specimens (251 males and 338 females) were captured in the rivers of the Caxiuana National Forest, in the Brazilian state of Para, between July, 2008 and July, 2009. Among the male specimens, 171 were classified as adults and 80 as juveniles, while there were 249 adults and 89 juvenile females. Using a sinusoidal equation, analysis of the GSI revealed a reproductive asynchrony between the genders, with males attaining their highest GSI values in January, while females peaked in March. For males, the sinusoidal regression for GSI values was significant only when used the complete data set (P=0.001), wears no trend was identified for bimonthly means (P=0.136). For females, by contrast, significant values were obtained for both the complete data set (P=0.012) and bimonthly GSI means (P=0.026). For the condition factor, the sinusoidal equation returned significant seasonal variation in both raw data (P=0.02) and with mean values (P=0.00) for males, but only with raw data for females (P=0.04), which appears to reflect variation in the energy budget between genders. With regard to the sex ratio, more reproductive females were captured than males in January and March, 2009, which suggests a pattern of segregation related to the reproductive process. These parameters are fundamental to the assessment, protection, and management of natural fish stocks, as well as providing guidelines for the development of conservation strategies.

A New Species of Corydoradinae Catfish (Ostariophysi: Siluriformes: Callichthyidae) from Rio Solimões Basin, Brazil

Abstract A new species of Corydoras from the Rio Urucu basin, a right-bank tributary of the Rio Solimões is described. The new species shares a distinctive pigmentation pattern with Corydoras arcuatus, C. gracilis, and C. narcissus, composed of a uniform light ground color on the body, and a dark, arched stripe from tip of snout to caudal-fin base along the upper portion of the dorsolateral body plates. The new species is readily distinguished from these congeners by the absence of a continuation of the arc-like stripe onto the snout. It also differs from Corydoras gracilis and C. narcissus by the posterior part of the arc-stripe reaching the base of the lower caudal-fin rays, and from C. arcuatus and C. narcissus by the distinctly rounded profile of the snout in lateral view, a greater preadipose distance, and the position of the posterior limit of the cleithrum. Despite the general resemblance, investigation about the position of the new species in light of previous phylogenetic hypotheses concerning this subfamily indicates that the arc-striped coloration pattern was independently acquired.

Reproductive characteristics and the weight-length relationship in Anableps anableps (Linnaeus, 1758) (Cyprinodontiformes: Anablepidae) from the Amazon Estuary

The present study analyzed the length-weight relationship and some aspects of the reproductive biology of Anableps anableps from the mouth of the Maracana River, in the Brazilian state of Para. The specimens were collected using two 30 m-long gillnets with 15 and 20 mm mesh size, as well as a 1 m-diameter hand net with a 10 mm mesh. A total of 865 specimens were collected, from which an adult sex ratio of 2.12 females per male was recorded (χ² = 13.07; p<0.05). Females presented positively allometric growth, whereas males were negatively allometric. In the additional analyses, the gonads of 371 female specimens were observed microscopically. Gonadal development was classified in three stages: immature (5.0%), maturing (12.0%), and mature (83.0%). Embryonic development was classified in five phases, according to the size of the embryo and the vitelline sac. Mean fecundity was 12 eggs/embryos per female (range: 1-37 eggs/embryos). A significant relationship was recorded between the standard length of females and ovaries weight (R² = 0.257; p < 0.001), and the number of embryos carried (R² = 0.573; p < 0.001). Mean body length of females at initial sexual maturation (L50) was estimated at 11.7 cm. The species reproduced throughout the year.

Feeding ecology of Auchenipterichthys longimanus (Siluriformes: Auchenipteridae) in a riparian flooded forest of Eastern Amazonia, Brazil

Neste estudo foram investigados os habitos alimentares do bagre Auchenipterichthys longimanus coletados em rios da Floresta Nacional de Caxiuana (Amazonia Oriental, Brasil) ao longo de diferentes periodos hidrologicos (seco, enchendo, cheio e vazando). Foram coletados 589 especimes durante sete amostragens, entre julho de 2008 e julho de 2009, dos quais 74eram machos jovens, 177 machos adultos, 89 femeas jovens e 249 femeas adultas. A composicao da dieta, analisada pelo Indice de Importância Alimentar (IAi%) foi avaliada por um escalonamento multidimensional nao-metrico (nMDS) e pela analise de similaridade (ANOSIM), que incluiu 37 itens alimentares agrupados em nove categorias (insetos aquaticos, outros invertebrados aquaticos, fragmento de artropodes, peixe, fragmento de planta, sementes, insetos terrestres, outros invertebrados terrestrese vertebrados terrestres). Tambem foram obtidos a amplitude de nicho (Indice de Levins) e o Indice de Replecao (IR%) da dieta do bagre. Foram observadas diferencas na composicao da dieta entre os periodos hidrologicos, principalmente relacionada a estacao seca e cheia, mas nao houve variacao na composicao da dieta entre os sexos e maturidade. No periodo de cheia (especificamente no mes de marco/2009) o bagre mostrou uma alimentacao mais especialista enquanto que no periodo de seca (novembro/2008) os valores de amplitude de nicho classificaram-no com habitos mais generalistas quanto a alimentacao. A quantidade de alimentos ingeridos por A. longimanus com base no Indice de Replecao (IR%), nao diferiram significativamente entre o sexo e maturidade. No entanto, foram evidenciadas diferencas quando comparados os meses estudados. Estes resultados fornecem informacoes biologicas importantes sobre a ecologia trofica de peixes da familia Auchenipteridae. Tendo em vista a maior ocorrencia de itens aloctones na dieta deste bagre, esta pesquisa tambem reforca a importância das matas ciliares em ambientes criticos na manutencao e conservacao das populacoes selvagens de peixes na bacia amazonica.

Feeding ecology of Dash-dot Tetra Hemigrammus belottii(Steindachner 1882) (Characiformes: Characidae) in the streams of the Urucu River basin, central Amazonia, Brazil

O presente estudo descreve a dieta da especie Hemigrammus belottii (Characiformes: Characidae) coletados na bacia do Rio Urucu no municipio de Coari, Amazonas, (Brasil), buscando responder o seguinte questionamento: Qual a influencia dos periodos hidrologicos (seco e chuvoso) e da distribuicao espacial na dieta de H. belottii? Os especimes tiveram seus estomagos retirados e os itens alimentares pesados e identificados para posteriores analises relacionadas a intensidade alimentar, pelo Indice de Replecao (IR%) e pelo indice de importância alimentar (IAi%). Foi analisado um total de 227 especimes, com comprimento padrao medio de 16,54 mm ± 5,6 mm. Baseado no IR% verificou-se para H. belottii uma maior intensidade alimentar durante o periodo da seca. A dieta da especie foi composta predominantemente pelos itens Formicidae (IAi% = 69,6), fragmento de exoesqueleto aloctone (IAi% = 17,7) e Coleoptera (IAi% = 6,0), com sua composicao se mostrando independente de periodos hidrologicos e de sua distribuicao espacial, que pode ser atribuido a alta disponibilidade de itens alimentares utilizados pela especie durante o ano todo. De um modo geral H. belottii evidenciou um habito alimentar insetivoro generalista, com predominio de itens de origem aloctone.

Length-weight relationship and reproduction of the guppy Poecilia reticulata (Cyprinodontiformes: Poeciliidae) in urban drainage channels in the Brazilian city of Belém

This paper describes the length-weight relationship, size at first maturation (L), and breeding season of Poecilia reticulata found in drainage channels on the campus of the Federal University of Para (UFPA) in the Brazilian city of Belem. A total of 1.936 specimens (942 males and 994 females) were collected in monthly samples of the study area between June, 2006, and March, 2007. Females were significantly longer and heavier than males. The length-weight relationship for males was established by the equation Pt = 5 × 10-5 × Ct2.397 and for females by Pt = 3 × 10-6 × Ct3.419. The estimated value of L was 17.5 mm for males and 20.4 mm for females, suggesting that males initiate reproductive activity at a smaller size than females. The abundance of mature females did not vary significantly among months, and there was little variation in the sex ratio, which was close to parity overall. Despite the adverse conditions encountered in the UFPA drainage system, P. reticulata appeared to have adapted its biological processes adequately.

Edge effects and the impact of wildfires on populations of small non-volant mammals in the forest-savanna transition zone in Southern Amazonia

O efeito de borda e do fogo sobre a comunidade de pequenos mamiferos nao-voadores foi investigada em uma area de transicao entre Cerrado e Floresta em uma area de matriz de soja na Amazonia Oriental. Os individuos foram coletados em 24 transectos, dos quais 16 foram distribuidos em area sem efeito do fogo e oito distribuidos com efeito do fogo. Um total de 11 especies foi registrado, incluindo seis roedores e cinco marsupiais. A especie Hylaeamys megacephalus foi a mais abundante em areas sem efeito do fogo. A abundância e riqueza de pequenos mamiferos nao-voadores apresentaram uma diminuicao em areas queimadas, entretanto o efeito do fogo parece mascarar o efeito de borda nestas mesmas areas. Em relacao ao efeito de borda, sem nenhum efeito de fogo, a relacao entre a abundância de pequenos mamiferos nao-voadores com a distância da borda foi positiva. A relacao entre a diversidade de pequenos mamiferos e efeito de borda pode ser ligada a vegetacao matriz e caracteristicas ecologicas de cada especie.

Forest reserves and riparian corridors help maintain orchid bee (Hymenoptera: Euglossini) communities in oil palm plantations in Brazil

Orchid bees (Apidae, Euglossini) are important pollinators in the Amazon forest. In eastern Brazilian Amazon, secondary forest and pastures are being replaced by oil palm plantations. Here, we tested the role of forest reserves and riparian corridors in maintaining orchid bees. We sampled bees in three different soil-type uses, comparing richness, abundance, and assemblage composition. Estimated richness was lowest in palm plantations than in forest reserves and riparian corridors on diversity of orchid bees. Riparian corridors had the highest abundance, followed by reserves, and oil palm plantations. Bee assemblage also varied with land cover, with the reserves having the most distinct composition. We also identified indicator bees for primary forest. Our results demonstrate riparian corridors and forest reserves can maintain orchid bees in oil palm landscapes.

Length-weight relationship in ten fish species from the Nhamundá River, the Amazon Basin, Brazil

Studies on the length-weight relationship (LWR) of fishes are an important tool to describe several biological aspects of the species. Consequently, these studies are relevant due the necessity of comprehension about fish life cycle. Thus, this study aimed to establish the length-weight relationship of the ten most common fish in the Lower Nhamunda River, left tributary of the Amazon River. The capture of fish was conducted in January 2008 using gill nets. A total of 807 individuals, ten species and three Orders (Characiformes, Siluriformes and Clupeiformes) were analyzed. The parameter b varied from 2.680 to 3.698. The LWR were shown for the first time for two species: Anostomoides laticeps and Ageneiosus polystictus. Finally, this research emphasizes the importance of LWR studies in the Amazon and the use of primary data for fisheries management plans.

Feeding ecology of Serrasalmus gouldingi (Characiformes: Serrasalmidae) in the lower Anapu River region, Eastern Amazon, Brazil

Studies on feeding ecology of fishes are important to understand the relationship between species and environmental seasonal variations. In tropical rivers, these relationships are mainly modeled by hydrological patterns. Thereby, this study aimed to assess the influence of fluviometric variation and life stage (juveniles and adults) in the feeding ecology of Serrasalmus gouldingi in the lower Anapu River region, located in Eastern Amazon, Para, Brazil. Specimens were collected bimonthly, considering four different hydrological periods. We assessed the diet composition, feeding intensity and niche breadth of the species. Thirty-two dietary items were identified and grouped into ten categories. A total of 279 stomachs were analyzed, showing a predominance of fish fragments, followed by fruits and seeds. The diet composition of S. gouldingi differed only between drought and flood season, although it did not differ between juveniles and adults. An increase in feeding intensity was recorded during the rise in the water level, with a lower feeding intensity observed during transitional season. Serrasalmus gouldingi showed lower niche breadth during flood season, attributed to the high consumption of fruits and seeds, presenting an omnivorous diet with high tendency towards piscivory. Although less evident than in other Amazon watersheds, the flood pulse in the lower Anapu River region is an important factor influencing the feeding ecology of the species.