Effects of early developmental stress in Apis mellifera

Early developmental exposure to even low dosages of a stressor can have persistent effects on the individual’s adult morphology, physiology and developmental rate and behavior. Honeybee larvae are particularly susceptible to stressors, but sublethal stress effects on honeybee larvae are insufficiently explored. Such sublethal effects may be a significant contributor to declining honeybee health. We studied the persistent effects of acute early developmental exposure to various sub-lethal dosages of the organophosphate coumaphos, the oxidative stressor paraquat, injection/feeding of lipopolysaccharide, and heat shock applied at the 5^th instar before capping. We choose to focus on the 5^th larval instar as it acts as a transitional point between larvae and pupation and ensures a worker-destined metamorphosis. Daily censuses were made during the pupation period to record any difference in developmental time and early mortality. Fluctuating asymmetry (FA) of emerging individuals was used to assess the early developmental impact of each acute stressor. These same individuals were then screened for stressor-specific biomarkers to evaluate molecular consequences. Daily observations on additionally marked individuals were used to measure differences in longevity and age of first foraging. Finally, we evaluated adult developmental rate by constructing hives composed only of emerging individuals from each treatment group and recording their age of first foraging.