Genotoxic and oxidative stress responses induced by amoxicillin in milkfish Chanos chanos (Forsskål, 1775)

Industrial, healthcare, and agricultural activities have led to increased antibiotic contamination, raising environmental concerns. This study investigated the toxicity of amoxicillin (AMX) in Chanos chanos fingerlings, assessing genotoxicity through micronucleus (MN) and nuclear aberrations (NA) assays and oxidative stress using thiobarbituric acid–reactive species (TBARS) analysis. Fish were exposed to nominal AMX concentrations of 1.746 µg/L (low), 3.453 µg/L (medium), and 5.160 µg/L (high), with samples collected on days 0, 3, 5, 7, and 14. indicated a dose- and time-dependent increase in MN and NA frequency, confirming AMX-induced genotoxicity. MN formation progressively increased across exposure groups, with a significant rise from day 3 onward. Similarly, NA frequency correlated with AMX concentration and duration, peaking at 31.33 NA per 1000 erythrocytes in the highest concentration group on day 14. These findings align with previous research linking AMX exposure to DNA damage and oxidative stress. TBARS analysis revealed that malondialdehyde (MDA) levels ranged from 5.29 to 86.31 nmol/mg tissue, with higher concentrations in high-dose exposure groups. More pronounced MDA elevation was observed at higher AMX concentrations, particularly at and above 3.453 µg/L, suggesting increased oxidative damage under elevated exposure conditions. However, because TBARS reflects lipid peroxidation only, these findings should be interpreted as evidence of oxidative membrane damage rather than complete impairment of antioxidant defense pathways. Taken together, the results suggest that AMX exposure may induce both genotoxic effects and oxidative cellular damage in Chanos chanos , with responses becoming more evident at higher concentrations and longer exposure durations. These findings emphasize the need for stricter regulations on pharmaceutical pollutants to mitigate their long-term impacts on aquatic ecosystems. • Amoxicillin exposure induces genotoxicity in Chanos chanos fingerlings. • Micronucleus and nuclear aberrations increase dose- and time-dependently. • Oxidative stress surpasses defense capacity beyond 3.453 µg/L AMX exposure. • Malondialdehyde levels confirm lipid peroxidation in liver tissues. • Findings highlight AMX’s ecological risks and need for stricter regulations.