Impact of chronic exposure to ternary metal mixtures on behavioral and cellular responses in <i>Nauphoeta cinerea</i> nymphs

There is a growing concern about the impact of environmental contamination by metals on insects owing to their biodiversity and important ecological roles. We investigated the neurobehavioral traits, cellular responses, and levels of metals in tissues of Nauphoeta cinerea nymphs exposed, separately and in ternary mixtures, to arsenic (15 and 7.5 mg/L), copper (15 and 7.5 mg/L), and zinc (100 and 50 µg/L), in drinking water for 35 consecutive days. Results showed that the diminutions in locomotor parameters (maximum speed, motility time, and distance traveled), motor and turning capabilities (path efficiency, turn angle, and body rotation) and the increase in anxiety-like behavior (total time freezing and freezing episodes) were more pronounced in individual metal exposure than triple metal mixtures groups. Barring zinc alone group, acetylcholinesterase activity decreased significantly in all the treatment groups compared to the control. The diminutions in glutathione level and antioxidant enzyme activities were partially attenuated in the fat body, midgut, and head of insects in the triple metal mixtures groups. Further, the levels of nitric oxide, hydrogen peroxide, lipid peroxidation, and reactive oxygen and nitrogen species were higher in individual metal exposed insects than the ternary mixture groups. The concentrations of arsenic, copper, and zinc in the fat body, midgut, and head of insects were significantly higher in individual metal exposure groups than the ternary metal mixtures groups. Collectively, the detrimental effects of elevated ecological concentrations of arsenic, copper, and zinc were more pronounced in insects exposed to individual metal than those in ternary mixtures groups.