Honeybee optomotor behaviour is impaired by chronic exposure to insecticides

Honeybees use wide&[ndash]field visual motion information to
calculate the distance they have flown from the hive, and this information
is communicated to conspecifics during the waggle dance. Seed treatment
insecticides, including neonicotinoids and novel insecticides like
sulfoxaflor, display detrimental effects on wild and managed bees, even
when present at sublethal quantities. These effects include deficits in
flight navigation and homing ability, resulting in decreased survival of
exposed worker bees. Neonicotinoid insecticides disrupt visual motion
detection in the locust, resulting in impaired escape behaviours, but it
had not previously been shown whether seed treatment insecticides disrupt
wide&[ndash]field motion detection in the honeybee. Here, we show
that sublethal exposure to two commonly used insecticides, imidacloprid (a
neonicotinoid) and sulfoxaflor, results in impaired optomotor behaviour in
the honeybee. This behavioural effect correlates with altered stress and
detoxification gene expression in the brain. Exposure to sulfoxaflor led
to sparse increases in neuronal apoptosis, localized primarily in the
optic lobes, however there was no effect of imidacloprid. We propose that
exposure to cholinergic insecticides disrupts the
honeybee&[nprime]s ability to accurately encode
wide&[ndash]field visual motion, resulting in impaired optomotor
behaviours. These findings provide a novel explanation for previously
described effects of neonicotinoid insecticides on navigation and link
these effects to sulfoxaflor for which there is a gap in scientific
knowledge. --