3D standard brain of the sphinx moth Manduca sexta: sex-dimorphism and development
Basil El Jundi, Wolf Hütteroth, Joachim Schachtner
Tierphysiologie, Philipps-Universität Marburg
The basic properties of brain circuits are specified during development while shaping of the circuits occurs postnatal. Important tools to study changes in brain structure independent of individual variations are 3D standard atlases of defined brain areas. We use M. sexta to study brain development and plasticity, especially of areas involved in processing of olfactory information. In insects, odor information is first processed in the antennal lobes (AL) and then conveyed to higher brain centers. The AL are, similar to the vertebrate olfactory bulbs, organized in neuropilar substructures called glomeruli. The AL of M. sexta display a sex-dimorphism reflected by three specialized glomeruli which are in both sexes easy to identify by their shape, size and location. One aim of this study was to analyze whether this sex-dimorphism is restricted to the AL or is also present in other brain areas. Based on immunostainings against synapsin we reconstructed and standardized 15 brain areas plus seven ordinary glomeruli from 12 females and 6 males. Analysis of the data revealed no sexdimorphism in the ordinary glomeruli, while all other brain areas are substantially larger in females. During metamorphosis the brain undergoes considerable remodeling including new formation of neuropils, e.g. AL. To further understand mechanisms involved in the metamorphic transition of the brain, we chose 11 defined stages for brain reconstruction and generated a 4D visualization of brain development.