Neurogenesis is absent in the brains of adult honey bees and does not explain behavioral neuroplasticity

The mushroom bodies, the insect brain structures most often associated with learning, exhibit structural plasticity during adult behavioral development in honey bees. We have investigated whether adult neurogenesis contributes to the plasticity of the mushroom bodies by labeling the DNA of replicating cells with 5-bromo-2'-deoxyuridine (BrdU). Immunocytochemical analysis of brain sections from bees fed or injected with BrdU as well as from bees treated in vitro with BrdU revealed no labeled neuronal nuclei, regardless of age or behavioral status of the worker bee (1-day old, nurse, or forager). Our results demonstrate that neurogenesis in the adult bee brain is a rare event, if it occurs at all. Therefore, the structural changes observed in the bee brain during adult behavioral development must be explained by developmental processes other than neurogenesis.