Assessment of acute sublethal effects of clothianidin on motor function of honeybee workers using video-tracking analysis

Abstract Sublethal impacts of pesticides on the locomotor activity might occur to different degrees and could escape visual observation. Therefore, our objective is the utilization of video-tracking to quantify how the acute oral exposure to different doses (0.1–2 ng/bee) of the neonicotinoid "clothianidin" influences the locomotor activity of honeybees in a time course experiment. The total distance moved, resting time as well as the duration and frequency of bouts of laying upside down are measured. Our results show that bees exposed to acute sublethal doses of clothianidin exhibit a significant increase in the total distance moved after 30 and 60 min of the treatment at the highest dose (2 ng/bee). Nevertheless, a reduction of the total distance is observed at this dose 90 min post-treatment compared to the distance of the same group after 30 min, where the treated bees show an arched abdomen and start to lose their postural control. The treated bees with 1 ng clothianidin show a significant increase in total distance moved over the experimental period. Moreover, a reduction in the resting time and increase of the duration and frequency of bouts of laying upside down at these doses are found. Furthermore, significant effects on the tested parameters are observed at the dose (0.5 ng/bee) first at 60 min post-treatment compared to untreated bees. The lowest dose (0.1 ng/bee) has non-significant effects on the motor activity of honeybees compared to untreated bees over the experimental period.