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 Caxiuanã National Forest, in the Brazilian state of Pará, 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.O objetivo deste estudo foi avaliar alterações sazonais no índice gonadossomático (IGS%), fator de condição (K) e proporção sexual, a fim de determinar o período de atividade reprodutiva do bagre Auchenipterichthys longimanus (Siluriformes: Auchenipteridae), a partir da análise de exemplares coletados em igarapés da Floresta Nacional de Caxiuanã, estado do Pará, Brasil. Através de coletas bimestrais entre julho de 2008 e julho de 2009, foram capturados 589 exemplares de A. longimanus, sendo 251 machos e 338 fêmeas. Dentre os machos, 171 exemplares foram classificados como adultos e 80 foram jovens, e dentre as fêmeas, 249 eram adultas e 89 jovens. Por meio do estabelecimento de uma equação senoidal, a análise do IGS% evidenciou uma assincronia reprodutiva entre os sexos, pois os machos obtiveram maiores valores de IGS% em janeiro e as fêmeas apresentaram seu pico em março. Para os valores de IGS% de machos, a equação senoide mostrou-se significante somente para os valores brutos (P=0,001), sendo não identificada uma tendência com os valores médios do IGS% (P=0,136). Para as fêmeas, os valores de significância da equação senoide para o IGS% foram obtidos tanto para os dados brutos (P=0,012) quanto para os dados médios (P=0,026). Para o Fator de Condição, a equação senoide demonstrou variação nos valores brut...

Relationship between length and weight (LWR) is used to describe aspects concerning the life cycle of fish, but does not considers possible changes during the lifetime mainly due to the sexual maturation. Thus, this study aims to identify the size at first maturity of Auchenipterichthys longimanus (Siluriformes: Auchenipteridae) and infer if the reproductive engagement could change growth pattern, concerning the LWR. Estimates of the size at first maturity (L 50 ) were made by visual identification of gonadal development and through the gonadosomatic index (G SI ). L 50 was estimated as 12.5 cm for males and 13.0 cm for females when applied visual identification of gonads development. L 50 estimates increased to 13.05 cm for males and 13.7 cm for females when estimated from G SI values. LWR was adjusted by using a regular power function and through the polyphasic growth model, with proportionality and allometric coefficients changing in a two phases. The results indicate differences in the growth pattern concerning males and females, as well as polyphasic growth. The change in the growth pattern of the polyphasic LWR was estimated at 11.42 cm for males and 12.53 cm for females, suggesting that changes in the growth pattern can sign-out the attainment maturity in this catfish.O estudo da relação entre peso e comprimento é usado para investigar muitos aspectos do ciclo de vida dos peixes, mas não considera que o padrão de crescimento pode mudar durante o tempo vida, principalmente devido à maturação sexual. Desta forma, este estudo objetivou identificar o tamanho de primeira maturação do bagre Auchenipterichthys longimanus (Siluriformes: Auchenipteridae) e testar se início do engajamento reprodutivo pode ser responsável por mudanças no padrão de crescimento da espécie, concernindo à relação peso/comprimento. Estimativas de tamanho de primeira maturação sexual (L 50 ) foram realizadas por meio da identificação visual dos estágios de maturação e pelos valores do Índice Gonadossomático (IGS). O L 50 foi estimado em 12,5 cm para machos e 13,0 cm para fêmeas quando aplicados a identificação visual dos estágios de maturação. A estimativa do L 50 aumentou para 13,05 cm para machos e 13,7 cm para fêmeas quando aplicados os valores de IGS. A relação peso/comprimento foi ajustada utilizando uma função potência e pelo modelo de crescimento polifásico, com coeficientes de proporcionalidade e alométrico diferentes para duas fases. Os resultados indicam diferenças no padrão de crescimento de machos e fêmeas, além de um crescimento polifásico para ambos os sexos. A mudança no padrão de crescimento foi estimada em 11,42 cm para machos e 12,53 cm para fêmeas, sugerindo que essas mudanças podem estar associadas ao início da vida reprodutiva desse bagre.

Feeding habits of the midnight catfish Auchenipterichthys longimanus collected in rivers of the Caxiuanã National Forest (Eastern Amazonia, Brazil) were investigated through the different hydrological periods (dry, filing, flood and drawdown). A total of 589 specimens were collected throughout seven samplings between July 2008 and July 2009, of which 74 were young males, 177 adult males, 89 young females and 249 adult females. The diet composition (Alimentary index - Ai%) was analyzed by a non-metric multidimensional scaling (nMDS) and by the analysis of similarity (ANOSIM), which included 37 items grouped into nine categories (Aquatic insects, Other aquatic invertebrates, Arthropods fragment, Fish, Plant fragment, Seeds, Terrestrial insects, Other terrestrial invertebrates, and Terrestrial vertebrates). We also calculated the niche breadth (Levins index) and the repletion index (RI%). Differences in the diet composition between hydrological seasons were registered, primarily on diet composition between dry and flood season, but changes related with sex and maturity were not observed. The midnight catfish showed more specialists feeder habit in the flood period (March 2009) and more generalist habits in the dry season (November 2008). The amount of food eaten by A. longimanus based on repletion index (RI%), did not differ significantly from sex and maturity. However, we evidenced differences in RI% when comparing the studied months. These results provide important biological information about the trophic ecology of auchenipterids fish. In view of the higher occurrence of allochthonous items, this research also underpins the importance of riparian forests as critical environments in the maintenance and conservation of wild populations of fish in the Amazon basin.

We have investigated micronuclei and other nuclear abnormalities in peripheral blood erythrocytes of saddle cichlid, Aequidens tetramerus, in order to evaluate the genotoxic and mutagenic effects of copper sulfate. Specimens (n = 4) were subjected to copper sulfate 7,975 mg.L-1 with an equal control group (n = 4).The Mann-Whitney test was used to compare nuclear abnormality frequencies between control and treatment groups. Results showed statistically significant difference of altered cells amongst the exposed acarás and the control group. Our results emphasize the importance of the micronucleus test in the assessment of genotoxic effects in fish, which can be used as bioindicators of the exposure of human populations to chemicals with a genotoxic potential found in drinking water. RESUMO Neste trabalho, investigamos a freqüência de micronúcleos e outras anormalidades nucleares em eritrócitos periféricos do acará-sela Aequidens tetramerus, com o objetivo de avaliar os efeitos genotóxicos e mutagênicos do sulfato de cobre. Quatro espécimes foram submetidos ao sulfato de cobre 7,975 mg.L-1 e outros quatro constituíram o grupo controle. As freqüências de anormalidades nucleares foram comparadas pelo teste de Mann-Whitney. Os resultados apresentaram diferença estatisticamente significativa de células alteradas entre os acarás expostos e o grupo controle. Nossos resultados reforçam a importância do teste do micronúcleo na avaliação de efeitos genotóxicos em peixes, os quais podem ser utilizados como bioindicadores da exposição de populações humanas a produtos químicos com potencial genotóxico presentes na água de consumo.