Acute Toxicity of Anthracene on Behavior, Blood Biochemistry, and Organ Histopathology in Nile Tilapia, Oreochromis niloticus

ABSTRACT Anthracene is a widely detected polycyclic aromatic hydrocarbon in aquatic ecosystems, posing significant health risk to freshwater fish. However, acute effects of anthracene covering multiple health biomarkers in a commonly cultured and consumed freshwater fish Nile tilapia ( Oreochromis niloticus ) remain poorly understood. Therefore, this study evaluates the acute effects of anthracene on behavioral, mortality, hematological, and histological changes in key organs of Nile tilapia. The fish were exposed to anthracene for 96 h at nominal concentrations of 0, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 mg/L under semi‐static conditions. Behavioral changes and mortality were recorded at 6 h of interval, and survived fishes were sacrificed to evaluate hematological and histological endpoints after 96 h. Cumulative mortality increased with both increase in concentrations and progression of exposure duration, and probit analysis revealed 96‐h LC 50 as 2.153 mg/L. Behavioral abnormalities including surface gulping, hyperventilation, and hypoactivity appeared earlier and more frequently at higher concentrations. Blood glucose level (mg/dL) increased significantly ( p < 0.05), and hemoglobin level (g/dL) decreased from 0.4 mg/L onwards compared to the control. Besides, among the erythrocytic cellular deformities, twin cell, tear drop, elongated shapes increased significantly from 0.4 mg/L, but others such as fusion and spindle were pronounced from 0.8 mg/L compared to the control. In the case of nuclear abnormalities, micronucleus formation was found significantly enhanced from the 0.2 mg/L, but the others (i.e., binucleus, notched nuclei, nuclear bud, and nuclear bridge) increased from 0.4 mg/L and the following groups. Gill pathologies such as clubbing, lamellar degeneration, telangiectasis, and fusion emerged from intermediated doses (0.2–0.8 mg/L), but most pronounced at 6.4 mg/L. Liver lesions including melano‐macrophage center (MMCs), blood congestion, degeneration of bile duct, vacuolization, and necrosis emerged from 0.2 to 0.4 mg/L and intensified with increasing doses. Besides, renal alterations were detected as blood congestion and vacuolization at 0.2 mg/L, melano‐macrophage center at 0.4 mg/L, necrosis, and dilation of Bowman's capsule at 0.8 mg/L and above concentrations, intensified with higher doses. Moreover, intestine showed progressively severe lesions with increasing concentration including shortening of villus length, vacuolization, displacement of epithelium from laminar propria, hyperplasia, and beheading of villi. These findings collectively indicate anthracene as a potent toxicant capable of inducing severe mortality, behavioral disturbances, hematological alterations and tissue damage in major organs of Nile tilapia, highlighting potential ecological risks and need for continued monitoring of PAHs contamination.