Complex Cd–Pb Multigenerational Exposure Improves the Growth and Food Utilization of the Cutworm Spodoptera litura

Abstract

Concurrent exposure to cadmium (Cd) and lead (Pb) is prevalent in the environment, but information on the long-term impacts of complex Cd–Pb exposure on herbivorous insects, especially at low doses, is scant. We studied the effects of complex Cd–Pb exposure (4.06 mg/kg Cd and 12.5 mg/kg Pb) on the growth and food utilization of the herbivorous insect Spodoptera litura for 10 continuous generations. Cd or Pb ingestion, excretion and accumulation by insect at the different developmental stages was determined for ten generations. The weighted scores calculated by the analytic hierarchy process (AHP) on the basis of the parameters of survival, growth and food utilization indicated that complex Cd–Pb exposure had positive impacts on the insects, regardless of generations. Compared with Cd (4.06 mg/kg Cd) and Pb (12.5 mg/kg Pb) alone, complex Cd–Pb exposure showed antagonistic interactions. After exposure to complex Cd–Pb, although larvae significantly increased heavy metal uptake along with the elevated ECD and ECI, insects enhanced heavy metal excretion via the feces and puparium; consequently, heavy metal accumulation in the insect body significantly decreased. With increasing generations, the positive impacts of complex Cd–Pb stress on insects became increasingly obvious, and the uptake of Cd or Pb decreased while the excretion of Cd or Pb increased, which demonstrated that insect tolerance to Cd–Pb exposure at low concentrations increased over generations.

Transcriptome Analysis Reveals Antioxidant Defense Mechanisms in the Silkworm Bombyx mori after Exposure to Lead

“…Superoxide dismutase (SOD) is a ubiquitous enzyme family that catalyzes the dismutation of superoxide anions effectively. A study by Adesina [ 60 ] reported that SOD activity in insects treated with herbal insecticide formulations increased with the concentration and exposure time. Increased concentrations of active components in all treated samples stimulated SOD production, resulting in higher dismutation of superoxide anions (O 2− ).…”

Changes in the Biology and Susceptibility of Weevil (Cylas formicarius) to the Insecticide Spinetoram as a Response to Cadmium Contamination

“…However, in this study, the cadmium contents in sweet potato chips and weevils were not determined for all treatments, which need to be further clarified in the subsequent studies on Cd accumulation. In addition to appetite, heavy metals have other toxic effects on insects; in severe cases, they have adverse effects on the growth index, development duration, and mortality rate [ 15 , 46 , 47 ]. Exposure of insects to Cd 2+ can delay development [ 28 , 32 ].…”

“…Evaluation of the impacts of heavy metal exposure on herbivorous insects is particularly important for assessing eco-toxicological risk in food chains [ 46 ]. In addition, the development of insect heavy metal tolerance has probably led to the increase in their tolerance to pesticides [ 7 , 43 ], which may reduce the efficiency of pest chemical control and bring new challenges to pest control in the farmland with heavy metal pollution [ 46 ]. In this study, weevil resistance to spinetoram increased after exposure to a low level of Cd 2+ , but the sensitivity to B. bassiana was not affected by Cd contamination.…”

“…Microbial control may be more suitable for pest control in heavy metal-polluted areas than chemical control [ 7 ]. Admittedly, the cross-tolerance was tested under controlled conditions, which enhances our understanding of the effects of single heavy metal on insects but may not accurately reflect the characteristics of natural communities because heavy metal pollution in the field generally involves a variety of heavy metals, and their impacts on insects are more diversified and complicated [ 46 , 56 , 57 ]. Therefore, it is more meaningful to combine indoor experiments with field investigations to explore the insect resistance or tolerance under heavy metal exposure.…”