Commissural organization and brain segmentation in insects

摘要: Recent molecular data obtained in grasshopper and Drosophila suggest that the anterior insect brain comprises three neuromeres: (1) protocerebrum (PC); (2) deutocerebrum (DC); (3) tritocerebrum (TC). In contrast to embryonic neuromeres ventral nerve cord (VNC) each of which possess two commissures, PC TC only one, while DC does not appear a commissure at all. A reason for this asymmetry is likely be presence stomodeum, exerts profound influence on gross morphology developing brain, but also, as an inductive factor, its axon scaffold. Immunocytochemical anatomical studies adult deutocerebral neurons project commissural axons across midline association with both protocerebral tritocerebral commissures (TCC). This implies foregut bisects topologically within itself not, traditionally thought, between TC. Genetic experiments confirm these observations provide evidence different regulatory mechanisms being responsible formation opposed VNC.