The occurence of black spot disease in Astyanax aff. fasciatus(characiformes: characidae) in the Guaíba Lake basin, RS, Brazil

Black spot disease is common in freshwater fish and is usually caused by the metacercaria stage of digenetic trematodes, normally from the Diplostomidae family. The present study evaluated the prevalence and intensity of this disease in Astyanax aff. fasciatus(Teleostei: Characiformes) in the Guaíba Lake basin (RS, Brazil), including body parts assessment and the points of sampling with higher occurrence of black spots. Fish samples were taken seasonally from December 2002 until October 2004. The samples were collected with the use of a seine net at eleven points. The specimens were fixed in 10% formalin and stored in 70% ethanol. Black spot disease showed a low frequency in the Guaíba lake basin (2.07%) and no specificity to the species Astyanax aff. fasciatus was observed. A high prevalence among the individuals and high intensity of infection levels was found in the ventral and dorsal regions in relation to other body parts (e.g., pectoral, pelvic and anal regions). Among the sampling points studied, we observed a higher prevalence on samples collected at points Gasômetro, Saco da Alemoa and Sinos, located in open areas with less occurrence of mollusks.

A doença dos pontos pretos é comum em peixes de água doce, sendo provocada por metacercárias de trematódeos digenéticos, normalmente da família Diplostomidae. Este estudo avaliou a prevalência desta doença em Astyanax aff. fasciatus (Teleostei: Characiformes) da bacia hidrográfica do lago Guaíba (RS) e avaliou as regiões do corpo e pontos de amostragem de maior ocorrência. As amostragens foram realizadas sazonalmente de dezembro de 2002 até outubro de 2004 e os exemplares coletados com redes de arrasto do tipo picaré em onze pontos da bacia estudada. Os peixes foram fixados em formaldeído a 10% e conservados em etanol 70%. A doença dos pontos pretos demonstrou baixa freqüência para as amostras coletadas na bacia hidrográfica do lago Guaíba (2,07%) e não foi verificada especificidade com a espécie A. fasciatus. Maior prevalência e intensidade de infecção ocorreram nas regiões ventral e dorsal em relação às outras partes do corpo (ex: regiões peitoral, pélvica e anal). Entre os pontos estudados, foi observado elevada prevalência nas amostras coletadas nos pontos Gasômetro, Saco da Alemoa e Sinos, localizados em áreas mais abertas e com menor ocorrência de moluscos.

The occurence of black spot disease in Astyanax aff. fasciatus (characiformes: characidae) in the Guaíba Lake basin, RS, Brazil / Ocorrência da doença dos pontos pretos em Astyanax aff. fasciatus (characiformes: characidae) na bacia do lago Guaíba, RS, Brazil

Black spot disease is common in freshwater fish and is usually caused by the metacercaria stage of digenetic trematodes, normally from the Diplostomidae family. The present study evaluated the prevalence and intensity of this disease in Astyanax aff. fasciatus (Teleostei: Characiformes) in the Guaíba Lake basin (RS, Brazil), including body parts assessment and the points of sampling with higher occurrence of black spots. Fish samples were taken seasonally from December 2002 until October 2004. The samples were collected with the use of a seine net at eleven points. The specimens were fixed in 10% formalin and stored in 70% ethanol. Black spot disease showed a low frequency in the Guaíba lake basin (2.07%) and no specificity to the species Astyanax aff. fasciatus was observed. A high prevalence among the individuals and high intensity of infection levels was found in the ventral and dorsal regions in relation to other body parts (e.g., pectoral, pelvic and anal regions). Among the sampling points studied, we observed a higher prevalence on samples collected at points Gasômetro, Saco da Alemoa and Sinos, located in open areas with less occurrence of mollusks.

A doença dos pontos pretos é comum em peixes de água doce, sendo provocada por metacercárias de trematódeos digenéticos, normalmente da família Diplostomidae. Este estudo avaliou a prevalência desta doença em Astyanax aff. fasciatus (Teleostei: Characiformes) da bacia hidrográfica do lago Guaíba (RS) e avaliou as regiões do corpo e pontos de amostragem de maior ocorrência. As amostragens foram realizadas sazonalmente de dezembro de 2002 até outubro de 2004 e os exemplares coletados com redes de arrasto do tipo picaré em onze pontos da bacia estudada. Os peixes foram fixados em formaldeído a 10% e conservados em etanol 70%. A doença dos pontos pretos demonstrou baixa freqüência para as amostras coletadas na bacia hidrográfica do lago Guaíba (2,07%) e não foi verificada especificidade com a espécie A. fasciatus. Maior prevalência e intensidade de infecção ocorreram nas regiões ventral e dorsal em relação às outras partes do corpo (ex: regiões peitoral, pélvica e anal). Entre os pontos estudados, foi observado elevada prevalência nas amostras coletadas nos pontos Gasômetro, Saco da Alemoa e Sinos, localizados em áreas mais abertas e com menor ocorrência de moluscos.

The occurence of black spot disease in Astyanax aff. fasciatus (Characiformes: Characidae) in the Guaíba Lake basin, RS, Brazil.

Black spot disease is common in freshwater fish and is usually caused by the metacercaria stage of digenetic trematodes, normally from the Diplostomidae family. The present study evaluated the prevalence and intensity of this disease in Astyanax aff. fasciatus (Teleostei: Characiformes) in the Guaíba Lake basin (RS, Brazil), including body parts assessment and the points of sampling with higher occurrence of black spots. Fish samples were taken seasonally from December 2002 until October 2004. The samples were collected with the use of a seine net at eleven points. The specimens were fixed in 10% formalin and stored in 70% ethanol. Black spot disease showed a low frequency in the Guaíba lake basin (2.07%) and no specificity to the species Astyanax aff. fasciatus was observed. A high prevalence among the individuals and high intensity of infection levels was found in the ventral and dorsal regions in relation to other body parts (e.g., pectoral, pelvic and anal regions). Among the sampling points studied, we observed a higher prevalence on samples collected at points Gasômetro, Saco da Alemoa and Sinos, located in open areas with less occurrence of mollusks.

Histopathological alterations observed in the liver of Poecilia vivipara (Cyprinodontiformes: Poeciliidae) as a tool for the environmental quality assessment of the Cachoeira River, BA.

Histopathological alterations in liver have been widely used as a tool in studies for monitoring environmental quality. To evaluate the environmental quality in the Cachoeira river, five spots were monitored between the municipal districts of Itapé and Ilhéus, using liver histological analysis. The species chosen for analysis was Poecilia vivipara due to the fact that it is one of the most abundant in the sampling. The routine technique of inclusion and impregnation in paraffin was used, and the cuts were stained with Hematoxylin and Eosin (H & E). Histopathological alterations in the liver were evaluated semi-quantitatively and based on the severity of the lesions. The results of the histopathological alteration frequency together with the average taken from the Histopathological Alteration Index from points 1 (Vila de Itapé) and 2 (Fazenda Santa Amélia) showed that in this area the environment is more threatened because of some stressor agent, possibly contaminants that seem to be acting in the environment and endangering the health of fish. The statistic results demonstrated that there were no significant differences among points 1, 2 and 4, which means they are very similar to one another, and are ecologically endangered.

Histopathologic alterations observed in fish gills as a tool in environmental monitoring.

The gills of fish have a great external contact surface and are particularly sensitive to chemical and physical changes in the aquatic environment. The aim of this study was to examine the histopathologic alterations in the gills of Astyanax fasciatus and Cyanocharax alburnus and to determine if there is a correlation between the severity of the alterations and environmental degradation and if this biological system can be used as a tool for evaluating water quality in monitoring programmes. The gills of 107 specimens of Astyanax fasciatus and 116 of Cyanocharax alburnus were collected seasonally and processed using routine histologic techniques for fixing and embedding in paraffin and staining of sections with haematoxylin and eosin. The main alterations observed in both species were alteration of the structure of the epithelium, vacuolisation, hyperplasia of the epithelium of the primary lamella, epithelial lifting, and alteration of the structure and occurrence of aneurysms in the secondary lamella. The locations Gasometer and F. do Celupa were the ones that showed the highest frequencies of moderate and severe alterations as the highest "histopathologic alterations index" means. The most severe alterations were found to be related to the most impacted environment, indicating the presence of stressors in the water.

Effects of bacterial infestation caused by human wastes on the skin structures of Mugil platanus Günther, 1880 (Mugilidae).

Manifestation of infectious pathologies in fishes usually increases in environments where organic wastes are disposed. Specimens of Mugil platanus Günther, 1880 and water samples collected at three points of the Tramandaí river were analyzed during a one year period. The macroscopic observation revealed ulcerations in the caudal peduncle area covered with a mass of amorphous and whitened tissues. Histopathologic analysis showed the presence of negative gram bacteria, probably responsible for alterations of the normal structure of the epidermic tissues. Non-parametric statistical analysis for ammonia concentration showed a significant variation among the three collected spots as well as in the multiple comparison between two spots. In this study, we describe cutaneous lesions observed in Mugil platanus specimens and tested their correlation with environmental ammonia concentration.

Effects of bacterial infestation caused by human wastes on the skin structures of Mugil platanus Günther, 1880 (Mugilidae) / Efeitos da infestação de bactérias provocada por resíduos humanos na pele de Mugil platanus Günther, 1880 (Mugilidae)

Manifestation of infectious pathologies in fishes usually increases in environments where organic wastes are disposed. Specimens of Mugil platanus Günther, 1880 and water samples collected at three points of the Tramandaí river were analyzed during a one year period. The macroscopic observation revealed ulcerations in the caudal peduncle area covered with a mass of amorphous and whitened tissues. Histopathologic analysis showed the presence of negative gram bacteria, probably responsible for alterations of the normal structure of the epidermic tissues. Non-parametric statistical analysis for ammonia concentration showed a significant variation among the three collected spots as well as in the multiple comparison between two spots. In this study, we describe cutaneous lesions observed in Mugil platanus specimens and tested their correlation with environmental ammonia concentration.

A manifestação de patologias infecciosas em populações de peixes costuma ser incrementada em ambientes onde são lançados despejos orgânicos. Exemplares da espécie Mugil platanus Günther, 1880 coletados em três pontos do rio Tramandaí foram utilizados para análise das alterações, e amostras de água foram tomadas durante o período de um ano para verificação da presença de bactérias. A observação macroscópica revelou ulcerações na região do pedúnculo caudal revestidas por uma massa de tecido amorfo e esbranquiçado. A análise histopatológica mostrou a presença de bactérias gram negativas, que provavelmente foram as responsáveis pela alteração da estrutura normal dos tecidos de revestimento do corpo. O resultado da análise estatística não paramétrica para a concentração de amônia mostrou variação significativa entre os três pontos amostrados bem como nas comparações múltiplas entre os pontos dois a dois. Este trabalho descreve as lesões cutâneas observadas em Mugil platanus e testa sua correlação com a concentração de amônia.