Effects of ZnO nanoparticles in the Caspian roach (Rutilus rutilus caspicus).

Area of Science:

• Environmental toxicology
• Nanoparticle risk assessment
• Aquatic vertebrate ecotoxicology

Background:

• Limited understanding of zinc oxide nanoparticle (ZnO NP) toxicity concerning exposure concentration and duration.
• Focus on nanoparticle size effects has overshadowed other critical exposure parameters.
• Need for comprehensive studies on ZnO NP effects in aquatic organisms.

Purpose of the Study:

• Investigate the impact of varying ZnO NP exposure concentrations and durations on Zn compartmentalization in Rutilus rutilus caspicus (Caspian roach).
• Evaluate the effects of ZnO NPs on biomarker expression and histopathological alterations.
• Assess the efficacy of a depuration period in mitigating ZnO NP toxicity.

Main Methods:

• Determined concentration-response curves and median lethal concentration (LC50) for ZnO NPs.
• Exposed Caspian roach to ZnO NP suspensions at LC50 and 0.1x LC50 for 4 and 28 days.
• Conducted a 14-day depuration period post-exposure and analyzed Zn accumulation, biomarker activity, and histopathology.
• Compared ZnO NP effects with equivalent zinc sulfate (ZnSO4) concentrations.

Main Results:

• Highest Zn accumulation occurred in gills after sub-acute exposure (28 days), followed by liver, kidney, and muscle.
• Zn from ZnO NPs showed higher accumulation in gills, liver, and muscle compared to ZnSO4.
• Biomarker activity significantly increased post-exposure but returned to baseline after depuration.
• Histopathological analysis revealed dose- and duration-dependent lesions in gills, liver, and kidney, which partially regressed after depuration.

Conclusions:

• Exposure concentration and duration are critical factors in ZnO NP toxicity, influencing Zn bioaccumulation and adverse effects in aquatic vertebrates.
• While depuration can reverse some toxicological endpoints, complete recovery is not always achieved, indicating potential long-term impacts.
• Findings contribute to a better understanding of ZnO NP risk assessment in aquatic ecosystems, emphasizing the interplay between exposure parameters and biological responses.