Effects of waterborne cadmium exposure on hematological parameters, oxidative stress, and stress-related genes in crucian carp ( Carassius auratus )

Cadmium (Cd) is a non-essential and highly toxic heavy metal widely present in aquatic environments. However, studies investigating the toxic effects of Cd on crucian carp ( Carassius auratus ) are relatively few. This study aimed to evaluate the toxic effects of Cd by assessing hematological parameters, antioxidant responses, and the expression of stress-related genes in C. auratus exposed to waterborne Cd. A total of 180 healthy C. auratus (19.43 ± 1.5 cm and 170.00 ± 3.04 g) were exposed to Cd at concentrations of 0, 2, and 4 mg/L for 8 weeks, with three replicates per treatment. The exposure to Cd resulted in significant reductions in red blood cell (RBC) count, hemoglobin (Hb) concentration, and hematocrit (Hct) values. Moreover, the levels of total superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GPx) in the liver also decreased significantly, whereas malondialdehyde (MDA) content was increased significantly. The expression levels of CAT , copper (Cu)/zinc (Zn)-superoxide dismutase ( Cu/Zn-SOD ), heat shock protein 70 ( HSP70 ), heat shock protein 90 ( HSP90 ), and metallothionein ( MT2) genes were significantly upregulated. Overall, Cd exposure adversely affected the hematological parameters, induced oxidative stress, and altered the expression levels of stress-related genes. This study not only provides new insights into the toxic effects of Cd in C. auratus but also contributes to environmental monitoring research.