Different types of metal oxide nanoparticles (NPs) are being used for wastewater treatment worldwide but concerns have been raised regarding their potential toxicities, especially toward non-targeted aquatic organisms including fishes. Therefore, the present study aimed to evaluate the toxicity of copper oxide (CuO) NPs (1.5 mg/L; positive control group) in a total of 130 common carp (Cyprinus carpio), as well as the potential ameliorative effects of fenugreek (Trigonella foenum-graecum) seed extracts (100 mg/L as G-1 group, 125 mg/L as G-2 group, and 150 mg/L as G-3 group) administered to fish for 28 days. Significant changes were observed in the morphometric parameters: the body weight and length of the CuO-NP-treated fish respectively decreased from 45.28 ± 0.34 g and 14.40 ± 0.56 cm at day one to 43.75 ± 0.41 g and 13.57 ± 0.67 cm at day 28. Conversely, fish treated with T. foenum-graecum seed extract showed significant improvements in body weight and length. After exposure to CuO NPs, a significant accumulation of Cu was recorded in the gills, livers, and kidneys (1.18 ± 0.006 µg/kg ww, 1.38 ± 0.006 µg/kg ww, and 0.05 ± 0.006 µg/kg ww, respectively) of the exposed common carp, and significant alterations in fish hematological parameters and oxidative stress biomarkers (lipid peroxidation (LPO), glutathione (GSH), and catalase (CAT)) were also observed. However, supplementing diets with fenugreek extracts modulated the blood parameters and the oxidative stress enzymes. Similarly, histological observations revealed that sub-lethal exposure to CuO NPs caused severe histomorphological changes in fish gills (i.e., degenerative epithelium, fused lamellae, necrotic lamellae, necrosis of primary lamellae, complete degeneration, and complete lamellar fusion), liver (i.e., degenerative hepatocytes, vacuolization, damaged central vein, dilated sinusoid, vacuolated degeneration, and complete degeneration), and kidney (i.e., necrosis and tubular degeneration, abnormal glomerulus, swollen tubules, and complete degeneration), while the treatment with the fenugreek extract significantly decreased tissue damage in a dose-dependent manner by lowering the accumulation of Cu in the selected fish tissues. Overall, this work demonstrated the ameliorative effects of dietary supplementation with T. foenum-graecum seed extract against the toxicity of NPs in aquatic organisms. The findings of this study therefore provided evidence of the promising nutraceutical value of fenugreek and enhanced its applicative potential in the sector of fish aquaculture, as it was shown to improve the growth performance and wellness of organisms.
Keywords: blood parameters; fenugreek seed extract; freshwater fish; histomorphology; nanoparticle toxicity; oxidative stress.