Environmental genotoxicity assessment of an urban stream using freshwater planarians

Pollution is a major concern in urban areas. Due to its biological significance, genotoxicity should be a main focus for pollution biomonitoring, due mainly to the increasing complexity of the chemical environment in which organisms are exposed. Diluvio's Basin (Porto Alegre, RS, Brazil) is a heavily polluted urban ecosystem impacted by urban wastewater. Planarians are useful organism for evaluating environmental genotoxicity because of their high sensitivity, low cost, high proliferative rate and also because of their basal evolutionary position in relation to complex metazoans. Comet assay is a powerful and highly sensitive method of evaluating primary DNA lesions. Based on the unique features of planarians and the current environmental state of Diluvio's Basin, the aim of this work was to evaluate the genotoxic potential of this body of water using comet assay in planarians. Planarians were exposed to the water for 13 days in a laboratory and comet assay was performed in order to screen possible DNA damages. The results indicated an increasing gradient of damage towards basin's mouth. Such a gradient could be related to the gradual increase of pollutants among the different sample sites. Moreover, there seems to be a correlation between the urbanization gradient that exists within the watershed and the genotoxicity. Historical physical-chemical data was also gathered and examined for possible correlations with genotoxicity. Comet assay in planarians is a very promising test for environmental monitoring studies. Its application should be expanded.