Ecotoxicological impacts of benzo[a]pyrene on Ctenopharyngodon idella larvae: hemato-immunological disruption, genotoxicity, and histopathological alterations

Introduction: Environmental pollutants are increasingly recognized as critical modulators of fish immune-associated alterations, with significant implications for aquaculture sustainability. Benzo[a]pyrene (B[a]P), a persistent polycyclic aromatic hydrocarbon, represents a major aquatic contaminant capable of inducing immunotoxic effects in early life stages of fish. Methods: ) were exposed to 1, 10, and 100 µmol/L B[a]P for 14 days to investigate the impact of B[a]P on hemato-immunological alterations, cytotoxicity, genotoxicity, and histopathological responses in immune-related organs. Results: B[a]P induced hematological and cellular alterations associated with possible immunotoxic effects in grass carp larvae. Hematological disruption was accompanied by increased erythrocyte apoptosis, reflecting cytotoxic stress. Genotoxic damage was evident through elevated DNA strand breaks, micronuclei formation, and nuclear abnormalities, suggesting compromised cellular integrity. Histopathological analysis revealed severe alterations in the liver and spleen, including lymphoid depletion, vascular congestion, and pronounced melanomacrophage center (MMC) activation with hemosiderin accumulation, highlighting immune-associated alterations. Conclusion: Collectively, these findings demonstrate that B[a]P acts as a potent environmental immunotoxicant that disrupts immune-associated biomarkers, induces cytogenotoxic damage, and impairs key immune organs in fish larvae. This study provides insights into how environmental contaminants modulate fish possible immunotoxic effects and underscores the importance of pollution management strategies to support disease resistance and sustainable aquaculture practices.