Effects Of Imidacloprid On Activities Of Detoxifying Enzymes And Development On Apis Mellifera

Imidacloprid was widely used recently, inspite of high toxicity to honey bees. Imidacloprid canimpair the olfactory memory and cause obvious abnormal foraging behavior on honeybees, but little isknown on the detoxifying enzymes. The purpose of this work is to study the activities of detoxifyingenzymes and acetylcholinesterase when honeybees were challenged by different doses of imidacloprid.Imidacloprid was administered orally, topically and residual film methods under laboratory condition.Time-effects by sublethal concentrations imidacloprid was also investigated. In addition, influence ofsublethal concentrations imidacloprid on larva development and foraging ability of adult honeybeeworkers were evaluated. Results are summarized as follows:Worker bees were treated with imidacloprid by orally, applied topically on the thorax and residualfilm methods under laboratory conditions. Our results suggested that imidacloprid can enhance theactivity of P450when its dosage ranged from LC5to LC20for treatments applied orally and residualfilm methods, LC10to LC50for treatments applied topically. Compared to control maximum ratios ofP450are2.94,3.31and1.88for orally, applied topically and residual film methods respectively.Furthermore, it has been confirmed that CarE has been enhanced ranging from LC5to LC60in orallymethod and residual film methods, maximum ratios are1.68and1.38respectively. However, GSTs wasobserved that it has been fully enhanced with lower dose and restrained with high concertration duringtopical application, but the orally method has opposite results. Synergistic ratios pretreated with PBO,DEF and DEM were2.14,2.05and1.21, this result confirmed the enzymatic assays and suggested thatP450and CarE may play important roles in the imidacloprid detoxification. Acetylcholinesteraseactivities were restrained with all the three methods at diffenent concentration.Worker bees were treated with LC5concentrations of imidacloprid by orally, applied topically onthe thorax and residual film methods. Results showed that there was no significant difference in theactivity of CarE between imidacloprid treated and the control groups. P450activities fluctuatedsignificantly as time and8h was an important point. GSTs activities fluctuated significantly with thetopically administration. Acetylcholinesterase activities were changed significantly as time, increased atthe beginning, then dereased and increased again at last, the key point of time was6h,8h,10h,16h,20h.Eclosion rate of eggs was significaintly decreased when treated by LC5concentrations of imidacloprid,and the rate was dropped32%when compared to control. But LC5concentrations of imidacloprid hadno effects on pupation and eclosion rate, body weight, nectar and pollen foraging ability.