Abstract: Detoxification enzymes in insects are generally demonstrated as the enzymatic defense against foreign compounds and play significant roles in maintaining their normal physiological functions. In this study, protein contents and carboxylesterase (CarE), acid phosphatase (ACP), alkaline phosphatase (ALP), cytochrome P450-dependent O-demethylase and glutathione S-transferase (GST) activities of Bactrocera tau Walker were determined by biochemical methods. The results showed that protein contents and these detoxification enzyme activities of the fruit fly varied significantly when fed on different diets including cucumber, pumpkin, towel gourd, white gourd and balsam pear. For protein contents, they were highest on balsam pear while lowest on cucumber and white gourd. For these detoxification enzymes, the CarE activity was highest on cucumber and pumpkin, cytochrome P450-dependent O-demethylase and GST activities were highest on balsam pear, but ACP and ALP activities were lowest on cucumber and pumpkin, respectively. In addition, these detoxification enzyme activities were also significantly different in the larval, pupal and adult stages. Adults had the highest CarE activity, and larvae had the highest ALP, cytochrome P450-dependent O-demethylase and GST activities, but the lowest ACP activity. Generally, these detoxification enzyme activities in the pupal stage were lower than those in the larval and adult stages except for ACP. Based on the above results, it was inferred that these detoxification enzyme activities were closely related to host plant species and developmental stages of this fruit fly.

Key words: Bactrocera tau, diet-insect interaction, detoxification enzyme activity