Research Article: Pathological and genotoxic effects of the herbicide oxadiargyl on common carp (Cyprinus carpio) fingerlings

Acute toxicity and effects of sublethal concentrations of oxadiargyl herbicide (3% EC) were examined on DNA damage (Comet assay) and histopathological changes in common carp (Cyprinus carpio) fingerlings with average weight and length of 19.15±1.05 g and 10.09±0.47 cm, respectively. The fish were exposed to 0.1, 0.3 and 0.5 mg/L of the herbicide for 30 days. Estimated 96-h LC50 value for oxadiargyl in common carp was 0.6 mg/L. Histopathologically, no change occurred in different tissues of the control group, while marked lesions were induced in vital organs of fish that their severity was increased with enhancement of the herbicide concentration. Sublethal exposure to different concentrations of oxadiargyl induced: hyperplasia of lamellar epithelium, hyperemia, inflammatory cells infiltration, aneurysm and rod-like structures of secondary lamellae in gill tissues, as well as change in size and number of melanomacrophage centers in kidney and spleen tissues. Necrosis of tubular epithelium, hyperemia, and protein casts were also observed in kidney tissue. Focal necrosis, fragmentation, vaculization and shrinkage of myofibrils, and eosinophilic cytoplasm were observed in muscle tissues of exposed fish. Erythrocyte cells of fish exposed to sublethal concentrations of 0.1, 0.3 and 0.5 mg/L, showed 18.3%, 19.1%, and 31.5% tailed DNA, respectively, significantly higher than the control group (p<0.05). Moreover, exposure to oxadiargyl significantly decreased WBC, RBC, Hb, Hct compared with the control group (p<0.05). In conclusion, these results revealed that oxadiargyl is highly toxic to common carp with genotoxic and hematotoxic effects, as well as adverse effects on histopathology of vital organs.