Physiological costs of combined cadmium and glyphosate exposure in sub-adult Clarias gariepinus: Evidence from endocrine, metabolic and renal biomarkers

The increasing occurrence of heavy metals and herbicides in aquatic environments raises concern regarding their combined effects on organisms. This study evaluated the physiological responses of sub-adult Clarias gariepinus exposed to fixed-ratio cadmium chloride–glyphosate binary mixtures using endocrine, metabolic, renal, and hepatic biomarkers. A static bioassay used six treatments including control (0.00/0.00 mg/L) and five mixture concentrations: 6.18/12.36, 12.36/24.72, 18.54/37.08, 24.72/49.44, and 30.90/61.80 mg/L cadmium chloride/glyphosate, respectively. Each treatment had three replicates containing ten fish. Blood samples were collected to determine cortisol, glucose, creatinine, urea, aspartate aminotransferase, alanine aminotransferase, calcium, and total protein concentrations. Results revealed significant treatment-dependent increases in cortisol (F = 41.785, P < 0.001), creatinine (F = 17.135, P < 0.001), and glucose (F = 3.135, P = 0.049). Cortisol increased from 12.47 ± 3.88 ng/mL to 66.93 ± 1.91 ng/mL, while creatinine rose from 0.45 ± 0.04 mg/dL to 0.86 ± 0.09 mg/dL. Glucose concentrations increased from 82.49 ± 6.05 mg/dL to 99.17 ± 2.81 mg/dL. Conversely, AST, ALT, urea, calcium, and total protein did not differ significantly (P > 0.05). Pearson correlation demonstrated strong positive relationships between mixture concentration and cortisol (r = 0.845, P < 0.001) as well as creatinine (r = 0.768, P < 0.001). Findings demonstrate that fixed-ratio cadmium chloride–glyphosate mixtures impose physiological costs on sub-adult Clarias gariepinus, primarily through activation of endocrine stress pathways, disruption of energy metabolism, and impairment of renal function. Cortisol and creatinine emerged as sensitive indicators for monitoring toxic impacts in ecosystems.