Effects of the herbicide atrazine in neotropical catfish (Rhamdia quelen)

•Silver catfish health can be compromised on atrazine contaminated water.•Atrazine can be hepatotoxic and nephrotoxic.•The liver showed relevant biochemical, histopathological and physiological changes.•Gills showed changes in pavement cells and chloride cells.•The limit of 2 μg L−1 allowed by Brazilian legislation is not safe to R. quelen.

The exposure to a world-wide used herbicide atrazine (ATZ) (96 h exposure to 2, 10, and 100 μg L−1), was investigated on the freshwater fish Rhamdia quelen through a multi biomarker approach. Liver histopathology revealed leukocyte infiltration, hepatocyte vacuolization like steatosis and necrosis areas, leading to raised lesion index levels in all tested concentrations. The increase of free melanomacrophage numbers was observed. Gill filaments revealed considerable loss of the microridges on pavement cells at 10 and 100 μg L−1 of ATZ, and a significantly increased of chloride cell (CC) number and density on apical surface area at 100 μg L−1 of ATZ. CAT, GST, GPx, and GR activities were inhibited by all tested concentrations. GSH levels were reduced in individuals exposed to 100 µg L−1. Osmoregulatory function was also disturbed. We observed an increase of plasma magnesium concentrations at 10 µg L−1. Additionally the inhibition of branchial carbonic anhydrase activity was observed at 100 µg L−1. In the kidney, carbonic anhydrase activity decreased only in the group exposed to 2 µg L−1. These results suggest that ATZ, represents a potential ecotoxicological hazard and can be hepatotoxic and nephrotoxic even low concentrations. The current study was the first to show the nephrotoxic effect of ATZ in fish. Besides, in Brazil, the environmental protection agency (CONAMA) establishes that the maximum allowed level of dissolved ATZ in water is 2 μg L−1, but the present results showed that this concentration may cause histopathological, biochemical and physiological changes in R. quelen.