Responses of continuous cadmium exposure on some biological and physiological performance of cotton bollworm Helicoverpa armigera

A detailed effect of continuous exposure of Cd on an important pest of crops like Helicoverpa armigera is lacking in the current literature. The cadmium was provisioned at 1.25, 2.5 and 5 mg/kg in the artificial diet and fed to newly hatched larvae for at least three subsequent generations. The total developmental period and fecundity were severely affected with no larval hatching in treated insects. Total haemocyte count and differential haemocyte count (i.e., granulocytes and plasmatocytes) were decreased significantly compared to controls in treated insects. The antioxidant system (i.e., catalase, glucose-6-phosphate dehydrogenase, superoxide dismutase and peroxidase), and the two detoxifying agents glutathione-s-transferase showed increased activity compared to controls. The results of the acetylcholinesterase assay showed a decrease in activity. Increased rate of aspartate aminotransferase, alanine aminotransferase, uric acid and decreased rate of alkaline phosphatase and lactate dehydrogenase in the first generation but showing an increasing trend in next two generations. The acid phosphatase activity was increased in the first two generations but significantly reduced in the third generation. The discrepancy in all physiological activities corresponded with the histological study of midgut infrastructure. It is inferred from the obtained results that cadmium continuous exposure affects every system of any organism that may perform irreparable damages.