EMBRYONIC BRAIN TRACT FORMATION IN DROSOPHILA-MELANOGASTER

During embryogenesis in insects, the axon-scaffold of the brain is bui lt around the embryonic foregut which separates the anlagen of the bra in hemispheres. Here, we investigate this process in Drosophila and sh ow that the major longitudinal and horizontal tracts of the embryonic brain form superficially near the interface between the foregut and em bryonic brain hemispheres. We identify three types of cellular structu res which might be involved in tract formation. These are rows of glia l cells at the medial brain margin, cellular bridges composed of neuro nal somata and the epithelial surface of the foregut itself. The close proximity to the outgrowing axons suggests that the structures at the brain-foregut interface may play a role in the morphogenesis of embry onic brain tracts in Drosophila.