The effect of dirithromycin on some biological and biochemical characteristics of Galleria mellonella L.(Lepidoptera: Pyralidae)

The effect of a macrolid antibiotic dirithromycin on survivorship, development, sex ratio, male and female adult longevity, fecundity and hatchability of greater wax moth Galleria mellonella L. were investigated by rearing the first instar larvae on artificial diets in the laboratory condition. The effect of this antibiotic on important oxidative stress indicators; lipid peroxidation product, malondialdehyde (MDA) and protein oxidation products, protein carbonyl (PCO) contents and a detoxification enzyme, glutathione S-transferase (GST) activity in the midgut of 7th-instar larvae (last larval stage) of the insect were also investigated. The insect was reared from first-instar larvae on an artificial diets containing dirithromycin at 0.001, 0.01, 0.1 or 1.0% to adult stage. Relative to the control, the diets containing dirithromycin concentrations significantly resulted in decreased survivorshipin development stages (7th-instars, pupae and adults) of the insect. The highest concentration of dirithromycin (1.0%) significantly decreased adult yield from 81.9 ± 4.11 to 15.2 ± 3.63%. This concentration produced 5.5% male, 9.7 ± 3.60% famale. The highest dirithromycin concentration also significantly prolonged developmental time of the insect. This concentration significantly delayed pupal development by 4 days, and adult development by 2 days in comparison to control. Dirithromycin had no significant effect on male and female adult longevity. Dirithromycin at all concentrations resulted in significantly decreased fecundity. The highest concentration of this antibiotics lowered egg number from 83.4 ± 0.89 to 32.6 ± 2.82, hatchability from 72.5 ± 4.82 to 33.7 ± 9.97%.Dirithromycin significantly increased MDA and PCO contents in midgut of 7th-larval instar. This macrolid antibiotic at highest dietary concentration significantly increased MDA content from 0.054 ± 0.002 to 0.19 ± 0.02 nmol/mg protein (3.5-fold), PCO content from 113.53 ± 4.4 to 640.84 ± 48.2 nmol/mg protein (6-fold) in comparison to control. However, only 0.1 and 1.0% dirithromycin significantly resulted in increased GST activity (7-fold). These concentrations increased GST activity from 2.24 ± 0.8 to 16.01 ± 3.0 and 16.68 ± 4.0 ? mol/mg protein/min respectively.This study showed a concentration-dependent variation in biological traits of the insect, and oxidative status and detoxification capacity of midgut. The results also showed these biological and oxidative effects might be altered in response to the perceived levels of dirithromycin-induced oxidative stress. We concluded that the lethal and sublethal effects of dirithromycin are likely to have a significant impact on oxidative and antioxidative status of midgut as well as biological traits of pest insects.