Combined effect of pollen quality and thiamethoxam on hypopharyngeal gland development and protein content in Apis mellifera

Pollen diet is essential to nurse bees to develop hypopharyngeal glands (HPGs) and produce royal jelly to feed larvae. The effect of different diet regimes combined with pesticide exposure on the development of HPGs in honeybees was studied. In particular, a high-quality pollen mixture (high pollen diversity and protein content) and a low-quality diet (low pollen diversity and protein content) were combined with the chronic administration of thiamethoxam (10 and 40 mu g/L). The impact of these stressors was evaluated by measuring the size of HPG acini and the total protein content of bee heads in 8- and 12-day-old bees. Bees fed with sub-lethal concentrations of thiamethoxam and with the low-quality diet exhibited smaller and irregularly shaped acini. The total protein content in bee head was also affected by pesticide administration, while the pollen quality did not cause significant modifications. In conclusion, these results highlighted the importance of the food quality, considered as nutritional value and pesticide contamination, for the physiological development of honeybees.