Multi-biomarker Assessment in a Native Species Psalidodon eigenmanniorum Under Inorganic Mercury and Recovery Scenarios

The increasing contamination of water bodies with mercury raises concerns about its possible effects on aquatic organisms. The combined use of several biomarkers allows researchers to study the impact of a chemical at different levels of biological organization. In the present work, we determined the response of histological (gills and liver), somatic (condition factor and hepato-somatic index), and behavioral (predator–prey relationship, through the presentation of a computer-animated image) biomarkers in the native species Psalidodon eigenmanniorum exposed to 100 µg L−1 of inorganic Hg (IHg) during 96 h. We also assessed whether there was a change in the biomarkers analyzed after 7 days in Hg-free water compared with those exposed to IHg. In exposed fish, IHg caused damage to the gills and liver tissues. The condition factor showed no difference between IHg-exposed organisms and control organisms, while the hepato-somatic index was lower in IHg-exposed fish. As for the behavioral analyses, it was observed that the presentation of a stimulus induced changes in the behavioral responses of fish exposed to IHg, which showed a heightened state of alertness with respect to control. On the other hand, after 7 days in Hg-free water, the organisms generally showed no changes in biomarkers compared with IHg-exposed fish. Our results contribute new data on IHg toxicity in a native species and provide information on the plasticity of damage to reverse itself. Furthermore, this work provides baseline information for environmental assessments in water bodies where mercury is present.