Effects of dietary nickel on apoptosis of hemocytes of Spodoptera litura (Fabricius) larvae

Effects of dietary nickel on apoptosis of hemocytes of the 6th instar larvae of Spodoptera litura Fabricius were evaluated using flow cytometry and Laser Scanning Confocal Microscopy (LSCM) by feeding S. litura larvae with artificial diets amended with different concentrations of nickel (1, 5, 10, 20 and 40 mg/kg) for 3 generations. Results showed that the hemocyte apoptosis rate of the 1st generation larvae increased with the increasing nickel concentrations in diet, and the apoptosis rate in the treatment with 40 mg/kg nickel was significantly higher than that in other treatments. In the 2nd generation, the highest hemocytes apoptosis rate was recorded in the treatment of the larvae exposed to 5 mg/kg nickel. The apoptosis rates in the larvae stressed by higher concentrations of nickel were lower than that in control. The apoptosis rates in the larvae exposed to nickel for 3 generations showed similar concentration-responses with that in the 2nd generation. However, the apoptosis rates in the larvae stressed with higher levels of nickel were all significantly inhibited in comparison with that in control. Therefore, effects of nickel stress on apoptosis of S. litura larvae were related with the nickel concentration in diets and the larval generations that were stressed by nickel.