RESUMOOs efeitos de substâncias genotóxicas sobre o genoma de peixes tem sido objeto de muitos estudos, sobretudo daqueles que buscam estabelecer a resposta dos genes aos estímulos ambientais. O presente trabalho teve como objetivo realizar um estudo sobre mutagenicidade e genotoxicidade em peixes elétricos da espécie Eingenmannia virescens, pela exposição ao benzeno (50ppm), utilizando as técnicas da Freqüência de Micronúcleos (MNs) e o Ensaio do Cometa. Foram coletadas amostras do sangue de dez peixes em diferentes tempos de exposição: T 0 , 24h, 48h, 72h, 96h e 360h (15 dias). Para a análise das lâminas no Teste do MN, foram contadas 1.000 células e estipulada a freqüência de ocorrência de MNs. Para análise do Ensaio do Cometa a contagem foi feita estipulando quatro classes de danos: I -II -III -IV, e para a análise estatística foram atribuídos valores numéricos (ranques) de 0 a 3, respectivamente, verificando diferenças significativas para a soma dos ranques em todos os tempos de exposição em relação ao T 0 . No Teste do Micronúcleo não foi possível detectar efeitos mutagênicos significativos nos eritrócitos analisados. No entanto, para o Ensaio do Cometa os resultados sugerem ação genotóxica do benzeno, devido a um aumento gradual no número de células com maiores classes de danos de acordo com maior tempo de exposição, indicando um efeito tempo-dependente. Estes resultados sugerem maior sensibilidade do Ensaio do Cometa que o Teste do MN. PALAVRAS-CHAVETeste do Micronúcleo; Ensaio do Cometa; peixes elétricos; eritrócitos Eingenmannia virescens, under to benzene exposure (50ppm), utilizing Micronuclei Test (MNs) and Comet Assay techniques. Ten fish blood samples were collected in different times of exposure : T 0 , 24h, 48h, 72h, 96h and 360h (15 days Avaliation of mutagenicity and gentotoxicity in Eigenmannia virescens (Teleostei: Gymnotiformes) exposed to benzene ABSTRACT The effects of genotoxic substances on fishes genome have been object of many studies, especially those which attempt to establish the responses of genes to environmental stimulus. The objective of this study was to evaluate the mutagenicity and genotoxicity in electric fishes of species

In this study we address the genotoxicity and putative mutagenic effects of benzene (BZN) in the erythrocytes of the electric fish Apteronotus bonapartii (Gymnotiformes, Apteronotidae) using the micronucleus test (MN) and comet assay, under controlled laboratory conditions. Electric fish were collected in the Solimões River, Manaus-AM, Brazil, and the specimens were exposed to 10 and 25 ppm concentrations of BZN, in 150L tanks. Blood samples were collected at 0 (T 0), 24, 48, 72 and 96 hours of exposure. For the concentration of 10 ppm BZN, the number of comets was significantly higher than T 0 levels after exposure of 48 hours, whereas the nuclear abnormalities (including MN) did not show any increase in relation to the controls (T 0) up to 96 hours. For the 25 ppm BZN, MN rates presented a significant increase after 72 hours, whereas other types of nuclear abnormalities increased in frequency after various exposure times, ranging from 24 to 72 hours. The number of comets increased significantly from 24 hours onwards for 25 ppm BZN. Both assays also showed a gradual increase in the number of damaged cells after longer exposure periods, indicating a time-dependent effect, especially at the highest BZN concentrations tested. This investigation reinforces the potential use of the endemic South American electric fish as a suitable genotoxicity biological model for biomonitoring purposes in the Amazon.

The relationship between the genes and the effects attributed to them has been object of many studies, especially those seeking to establish the response of genes to environmental prod. The aim of this work was to establish a standard system to monitor effluents by using juvenile Nile tilapia (Oreochromis niloticus) as a bioindicator of genotoxicity, utilizing micronuclei test and comet assay. For this, the fish were exposed during 24, 48, 72 and 240 hours (10 days), to water samples collected at two sites of the Itajaí-Açú River: Ilhota and Blumenau, in the Santa Catarina State, Brazil. For positive control the herbicide 2,4-D (75 ppm) was utilized, and the negative control of each fish were the values obtained before the exposure to the river water, termed time zero (T 0). Water samples from both sites of the Itajaí-Açú River showed significant genotoxic effects in erythrocytes of the exposed fishes. The comet assay was a more sensitive test to detect genotoxic damage in shorter exposure times (24 and 48 hours) than the micronuclei test.

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