LETHAL AND SUBLETHAL GLYPHOSATE EFFECTS ON NON-TARGET FISH SPECIES. BIOMARKERS RESPONSES IN CNESTERODON DECEMMACULATUS

MENÉNDEZ HELMAN R. J.; SALIBIÁN, A; DOS SANTOS AFONSO, M.

Handbook on Herbicides: Biological Activity, Classification and Health & Environmental Implications

Nova Science Publisher, Inc.

Lugar: New York; Año: 2013; p. 85 - 110

Environmental degradation in Latin America has increased in the last three decades. The agricultural frontier of Argentina is spreading out, and this phenomenon has involved a significant increase in the use of biocides. Glyphosate (N-phosphonomethylglycine, PMG) is the most widely used herbicide in this country. Particularly the application of formulated glyphosate increased from 70 million kg in 1999 to more than 210 million in 2011. Although this herbicide is considered as "environmentally friendly" with moderate persistence, the mobility and fate will be conditioned by the chemical and biological profile of the environment, and regarding that, several authors have determined environmentally relevant levels of glyphosate and its metabolites in surface water. The risk associated with the use of PMG, could be assessed by the evaluation of the impact on a non-target species: Cnesterodon decemmaculatus, a Neotropical endemic teleost, widely distributed in the region. Experimental results would indicate that glyphosate (active ingredient, analytical grade, acid form) does not present a high level of toxicity (LC50-96h > 100 mg.L-1) on C. decemmaculatus. However, the toxicity of one of the glyphosate-based herbicide formulation was found to be significantly higher (LC50-96h = 29 mg.L-1). These results are consistent with other evidences that indicate a remarkable increase in the toxicity of formulations regarding to the active ingredient in freshwater teleosts. Several scientists have focused their research on the identification of biomarkers of environmental stress in non-target species. These could be specific and early signals of the toxic-organism interaction. In this regard, the utility of morphological and biochemical parameters as quantitative bioindicators of xenobiotic exposure has been shown. Within this framework, we measured the impact of sublethal exposure of Cnesterodon decemmaculatus to PMG on antioxidant defenses (catalase activity) and neurotoxicity (acetylcholinesterase activity). After acute exposure, PMG caused changes in the enzyme activities: an increase in the activity of catalase and an inhibition of the acetylcholinesterase activity. These results are the first report indicating that sublethal PMG affect these biomarkers in a native teleost species.