Combined effect of pollen quality and thiamethoxam on hypopharyngeal gland development and protein content in Apis mellifera
This study describes the impact of sublethal doses of 4 pesticides on size and morphology of the honeybee worker’s hypopharyngeal glands. This gland plays an essential role in brood care by young workers, and thus colony growth. Contaminating 7 day old caged bees, we sampled after 1 day and 1 week for Captan-, Imidacloprid- and Indoxacarb-treated bees and after 1, 2, 3, 4, 5 and 7 days for Fenoxycarb-treated bees. The glands’ acini 1 week post-treatment were all significantly smaller in treated bees. However, lightand electron microscopy showed hardly any difference between controls and gland cells, treated with Captan, Imidacloprid or Indoxacarb. Yet upon Fenoxycarb-treatment, acini showed a decrease in size, a granular texture and unorganized cytoplasm more quickly than normal. Indeed, after only 7 days, Fenoxycarb-treated glands displayed features typical of the onset of foraging in older bees.