Micronucleus Test and Comet Assay in Erythrocytes of the Amazonian Electric Fish Apteronotus bonapartii Exposed to Benzene

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 Solimoes 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 (T0), 24, 48, 72 and 96 hours of exposure. For the concentration of 10 ppm BZN, the number of comets was significantly higher than T0 levels after exposure of 48 hours, whereas the nuclear abnormalities (including MN) did not show any increase in relation to the controls (T0) 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. Keywords: Comet assay, Micronucleus test, Apteronotus bonapartii, Benzene, Biomonitoring, Electric fish, Amazon