Genotoxicidade e citogenômica comparativa em peixes de igarapés poluídos de Manaus, Amazonas.

Abstract

Major advances and urban modifications in Manaus, the main city of the western Brazilian Amazon, began in 1970 with the establishment of an Industrial Pole known as Free Zone of Manaus. This accelerated urbanization process led to the occupation of improper urban areas, such as streams, which today serve as garbage dumps and receive industrial and hospital effluents. Several of these substances released daily in urban streams are capable of causing tissue damage in somatic and germ cell genetic material, as well as bioaccumulation of contaminants in the aquatic biota. Thus, we analyzed the genotoxic effects and investigated the chromosomal location of repetitive DNA sequences in fish from different polluted environments, aiming to infer events that favor the permanence of these organisms in urban streams in the city of Manaus. To this end, we studied (i) abiotic limnological profiles, (ii) genotoxic effects, (iii) methylation profiles and (iv) location of repetitive DNA sequences in six species of Amazonian fish and two species of exotic fish from three sites with more critical levels of environmental pollution in the city of Manaus (AM): Mindu stream, Quarenta stream and Tarumã-açu stream. As a negative control, the same species were collected in Catalão Lake, located at the confluence of the Negro and Solimões rivers. Overall, the results show that micronucleus analysis, erythrocyte nuclear abnormalities and the comet assay are important biomarkers for assessing the health of the aquatic ecosystem, especially in species that are exhibiting genetic and epigenetic remodeling due to poor water as a function of the water quality of the urban streams in the city of Manaus-AM, who suffer from environmental pollution. Additionally, the polluted environment may influence DNA methylation, which would have initially evolved as a defense mechanism of organisms against expression of transposable elements. The increase in the amount of Rex transposable elements on the chromosomes, evidenced in this study, represents its influence on the genome modeling of populations living in the polluted environment, where the structure, organization and function of the genome are modified in individuals exposed to environmental pollution. This is probably due to interactions with the transposable elements, which must be under constant adaptive evolution and respond to changing environments in a particular way for each species.