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|Title:||Neuroanatomical plasticity and division of labor in the honey bee (Apis mellifera)|
|Author(s):||Withers, Ginger Sue|
|Doctoral Committee Chair(s):||Fahrbach, Susan E.|
|Department / Program:||Neuroscience|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||There is an aged-based division of labor in the honey bee colony. Adult workers spend the first several weeks performing tasks within the hive, including caring for brood ("nursing"). They then make a dramatic behavioral transition and begin foraging outdoors. Within the dark hive, tasks are regulated primarily by chemosensory cues. A forager integrates both visual and chemosensory information, to successfully navigate through a dynamic environment. The onset of foraging is a natural, substantial behavioral experience, making the honey bee ideal for studying how the mature nervous system reorganizes to produce novel behavior.
Regional brain volume estimates of 1-day old bees, nurses, and foragers were made to assess the relationship between behavioral development and neuroanatomical plasticity. There was no overall change in the size of the brain, however, selective plasticity was observed in two regions: the olfactory glomeruli; and the mushroom bodies. Nurse bees had the greatest volume of olfactory glomeruli, perhaps reflecting the importance of chemosensory cues in regulating within hive tasks. An entirely different pattern occurred within the mushroom bodies, a region involved in complex behavior and learning. In this region, the ratio of neuropil to cell body volume was increased nearly two-fold in foragers compared with 1-day old bees, suggesting increased synaptic space per cell body.
Foragers are typically older than the other groups studied. To determine whether mushroom body reorganization was associated with behavior or age, a colony of young bees was created. Without older foragers, some young bees accelerate development. 7-day old foragers had the same mushroom body configuration as did older foragers, and were significantly different from 8-day old nurses. Age is therefore a less useful predictor of mushroom body organization than behavior.
Because increased levels of juvenile hormone (JH) are associated with the onset of foraging, the role of JH in mediating mushroom body changes was examined. Bees treated with hormone developed a mushroom body configuration similar to the typical forager, independent of foraging experience. This provides evidence that JH acts to reorganize the mushroom bodies, suggesting a potential mechanism by which this hormone regulates behavior.
|Rights Information:||Copyright 1993 Withers, Ginger Sue|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9411824|