Effects on Detoxification Enzymes in Different Life Stages of Honey Bees ( Apis mellifera L.,Hymenoptera: Apidae) Treated with a Synthetic Pyrethroid (Flumethrin)

The activities of two detoxification enzymes, glutathione S-transferase (GST) with 1-chloro-2,4-dinitrobenzene (CDNB) as substrate, and glutathione peroxidase with tert-butyl hydroperoxide as substrate (GSH-Px[TBH]), were measured in the larvae, pupae and adults of honey bees (Apis mellifera ligustica Spinola) originating from two colonies, one untreated acting as a control group and the other treated with flumethrin. The treatment with flumethrin led to increased GST activity in the larval instars, pupae and nurse bees compared with the control group. In particular, the late fifth larval instars (LS) and the pupal instars showed increased GST activities. GSH-Px[TBH] activities were highest in the early larval instars (L1–L2). Treatment with flumethrin resulted in the induction of GSH-Px[TBH] activity in the L4–L5 instars and LS. In the forager bees, the enzyme activity was lower in the group treated with flumethrin than in the control group. This could have been due to unknown extrinsic environmental factors. In general, the average protein contents were lower in the flumethrin-treated group than in the control group. In the LS and pupal stage, and in the adult worker bees, the differences were significantly lower. This inhibition of growth could be due to metabolic costs resulting from exposure to toxicants.