Fish inhabiting rice fields: Bioaccumulation, oxidative stress and neurotoxic effects after pesticides application

The present study aimed to evaluate the biological effects triggered by the application of a current-use mixture of pesticides (the herbicide glyphosate, the insecticide bifenthrin, BF, and the fungicides azoxystrobin, AZ, and cyproconazole, CYP) on two native fish (Markiana nigripinnis and Astyanax lacustris) inhabiting a rice field. We analyzed pesticide residues in water, sediment and fish samples 21 days before and after a fumigation event. Additionally, organismic indices, oxidative stress and neurotoxicity biomarkers in fish at both sampling periods were compared. After fumigation, glyphosate, BF, AZ and CYP were detected in water and sediment samples, being also bioaccumulated in both fish species. A decreasing condition factor in A. lacustris and a higher liver somatic index in M. nigripinnis were observed as well. Overall, results showed that, after the application of the pesticide mixture, antioxidant mechanisms failed to prevent oxidative damage in the liver and gills of M. nigripinnis. Meanwhile, A. lacustris showed a different response: an inhibition of the antioxidant defenses without tissue lipid oxidative damage. Furthermore, acetylcholinesterase activity after spraying was significantly reduced in brain and muscle tissues of A. lacustris and in the brain of M. nigripinnis. Our results show that currentuse pesticides, like glyphosate, BF, AZ and CYP, pose health risks on native fish populations inhabiting rice fields.