Genotoxicity of two pathogenic strains of zoosporic fungi ( Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus

Abstract

In the present work we have described the genotoxic potential of two pathogenic strains of zoosporic fungi ( Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus for the first time by three complementary tests: micronucleus test (MN), nuclear lesions (NL) and comet assay (CA). The groups exposed to the zoosporic fungi subjected to the MN and NL test showed statistically significant differences in MN and NL frequencies with respect to the control one. Also, a significant increase ( p<0.001) in micronuclei and nuclear lesions frequencies were recorded with the increase in exposure time. A correlation was observed between the frequencies of MN and NL, suggesting the importance for recording this anomaly in order to improve the information obtained with the MN test. Therefore, our results suggest that the nuclear lesions found here should be considered indicators of genotoxicity, in addition to the typical micronuclei forms. The result of the comet assay showed a significant difference in the percentages of the damaged DNA in the comet tail (%TDNA) of the treated groups comparing to the control. A significant ( p<0.001) increase in the DNA damage of the treated groups with the increase in exposure time was recorded, confirming the results of the MN and the NL tests. The results of the current study will be useful for future work involving the biomonitoring of regions where Nile tilapia survive. These data allow us to consider O. niloticus niloticus as a good bioindicator of the effects of genotoxic agents that might be present in the aquatic habitat.