Studies on the Effect of Cadmium Chloride on the Behavioral and Histopathological Changes in Cyprinus carpio : A Short-Term Bioassay

Cadmium (Cd) is a common heavy metal known for its detrimental impact on aquatic organisms. The presence of this non-essential element in the food chain poses a significant threat to human health due to its biomagnifying effects. The present study was undertaken to investigate the effects of cadmium toxicity on the behavioral and histopathological alterations in the gill, liver and kidney tissues of the common carp species, Cyprinus carpio. Six groups of experimental fish with three replicates were exposed to different concentrations of cadmium chloride i.e., 0, 60, 70, 80, 90 and 100 mg/L respectively for a period of 96 h. The 96 h LC50 value of cadmium chloride for C. carpio was determined to be 74.65 mg/L. Treated fishes with higher doses i.e., 80, 90 and 100 mg/L exhibited increased breathing, accelerated ventilation with rapid opercular movement and air gulping, erratic swimming, collision against wall, loss of equilibrium, jumping, restlessness and sluggishness. Histopathological changes were also observed in gill, kidney and liver tissue. The changes in gills were marked by lamellar fusion, epithelial hyperplasia, epithelial lifting, telangiectasia, lamellar aneurism, blood congestion and necrosis of epithelial cells. The trunk kidney of the exposed fish exhibited glomerular distortion, fibrous edema, infiltration of edematous fluid, expansion of Bowman’s space, hemorrhage, and damage in uriniferous tubules. The liver hepatocytes showed cytoplasmic vacuolation, pyknotic nucleus, hypertrophy of hepatocytes, erythrocyte infiltration, patchy degeneration, enlargement of sinusoids and loosening of hepatic tissues. The findings demonstrated that acute exposure to cadmium has a significant impact on the essential organs and normal behavior, potentially leading to harmful consequences for fish populations.