Urban intensity and runoff effects on oxidative stress and pathological severity in the testes and ovaries of blue crabs, Callinectes amnicola within a tropical lagoon system (Nigeria).

S. The spread of impermeable surfaces in urban coastal areas increases runoff, carrying pollutants that degrade surface water quality and impact the stress responses of coastal fauna. This study investigated oxidative stress and gonad health in male and female Callinectes amnicola (blue crabs) from urban and suburban regions of Lagos Lagoon. Gonadal damage in the crabs was linked to estrogenic metals (Cu, Zn, Pb, Cd) and antioxidant responses (MDA, GSH, GPx, CAT, and SOD). Urban male crabs showed higher oxidative stress, with elevated MDA and lower GSH and CAT levels, alongside regressive gonadal changes due to increased Pb, Cd, and Zn exposure. Suburban crabs, however, displayed more intersex conditions (ovotestes) correlated with elevated Cu levels in lagoon sediment. These results highlight severe testicular disruption in urban males and ovarian dysgerminomas in suburban females, indicating a sex-specific impact of pollution on reproductive health. The study identifies two primary reproductive toxicity risks: (1) male testicular damage and regressive lesions in urban crabs, caused by increased lipid peroxidation and oxidative stress, and (2) female endocrine disruption, with ovotestes in suburban populations potentially leading to nonviable follicles. These findings emphasize that urban blue crabs face significant risks across both sexes, while suburban populations are more affected by female-specific risks. The study underscores the need for targeted environmental management to address the different stressors impacting these populations.