Copper Resistance Selection and Activity Changes of Antioxidases in the Flesh Fly Boettcherisca peregrina

Natural populations of Boettcherisca (Sarcophaga) peregrina Robineau-Desvoidy (Diptera: Sarcophagidae) were maintained for 20 generations and reared either on unpolluted diet or on polluted diet containing copper at a median lethal concentration (LC50) determined every five generations. This resulted in two reliable strains: the relative susceptible strain (S) and the copperresistant strain (R). The metal accumulation, growth and development, reproduction, and antioxidant enzymes were analyzed in the two strains. The results showed that compared with the S strain, the R strain showed increased metal accumulation and fecundity of female adults. Regardless of whether larvae were fed on diet with or without Cu(2+), the R strain showed higher activity of superoxide dismutase and glutathione S-transferase than the S strain, although without statistical significance. Moreover, the activity of superoxide dismutase and glutathione S-transferase increased when B. peregrina larvae were exposed to Cu(2+) at 100 µg/g but decreased when they were exposed to Cu(2+) at 800 µg/g. Larval catalase activity in the R strain was higher than in the S strain when larvae were fed on diet with or without Cu(2+), although these differences were significant only at the 100 µg/g concentration. Moreover, the activity of catalase decreased when larvae were exposed to experimental Cu(2+). Beyond all expectations, larval glutathione reductase activity was not significantly different between the two strains but changed slightly when larvae were exposed to experimental Cu(2+). These results indicate that copper resistance in B. peregrina larvae is mediated by superoxide dismutase, catalase, and glutathione S-transferase. These results also help in establishing a physiological link between antioxidase activity and the resistance level of B. peregrina to copper.