Abstract:
Integrated Biomarkers Response (IBR) index have been developed as a practical and robust tool to assess the
susceptibility to pollutants using multiple biomarker responses. Neonicotinoid insecticides are nowadays one of
the most sold pesticides worldwide. Nevertheless, imidacloprid (IMI) sub-lethal effects such as oxidative stress
(OS) on fishes are scarcely studied. Hence, the aims of this work were: (1) to evaluate exposure- and damage
biomarkers related to OS in the freshwater fish Australoheros facetus exposed to IMI and (2) to apply the IBR
index to achieve a comprehensive understanding of OS in the fish. The results of the present study showed that
all the biomarkers presented different responses in the three monitored tissues: liver, brain and gills. Results for
an initial battery of 19 biomarkers were obtained and for the IBR index only those with significant differences
have been considered. The biomarkers that had the most important weight on the IBR index were SOD activity in
brain and gills, H2O2 concentration in liver, and carbonyl groups concentration in gills in fishes exposed to 100
and 1000 μg L−1 IMI. This index allowed affirming that a short term exposure to environmentally relevant
concentrations of IMI (≥10 μg L−1) produces OS in A. facetus. However, a more deep understanding of some
biomarkers response is necessary to improve the index and for finally apply it in field studies.