Abstract

Social-insect colonies often comprise thousands of individuals and have been described as “superorganisms”. The workers, as the main individual ‘unit’ for the functioning of the superorganism, show a highly adaptive behavioral repertoire enabling the colony to express emergent responses to varying environmental conditions. Variations in behavior such as the transition from an indoor worker to a forager, or learning and memory processes, have been correlated with neuroplastic changes in the brain. These changes in turn are influenced by age- and task-related processes and may be controlled by internal programs and environmental stimuli. After having taken volumetric analyses of neuropils as a widely used measure for neuroplasticity to the level of synaptic complexes, we now aim to gain a more detailed understanding of changes in synaptic circuits at the subcellular level. We currently push the limits of the so far achieved resolution in all three dimensions, and apply: 1) The correlative light electron microscopy technique “array tomography” to explore the distribution of synaptic proteins. The resulting identification and localization of molecular key components for neuronal plasticity provides an essential pre-requisite to manipulate behavior at the level of plasticity-related genes. 2) Electron tomography based 3D reconstructions to analyze the connectivity of pre- and postsynaptic partners, vesicle cargos and the precise 3D structure of active zones. We hypothesize that the reorganization of pre- and postsynaptic partners plays an important role in age- and experience-related changes in sensory processing and memory formation. Taken together these new approaches will allow us to further unravel the underlying mechanisms of neuronal plasticity in the hymenopteran brain.