Fig. 4.

Identification of commissures innervated by axons from central complex tracts prior to formation of the fan-shaped body in the grasshopper (a, b) and Drosophila (c – e). a. 3D confocal image following 8B7 labeling shows superimposed axon projections from the z tract (yellow), y tract (cyan) and x tract (magenta) concatenated with the general commissural system (blue), as viewed frontally, and spanning the depths from 80–107μm in the embryonic (e50%) grasshopper brain (c.f. Fig. 3). Colors are false. The projections are localized to anterior commissures: eAC III, eAC VIII, eAC IX; the median commissural system eM; and the dorsal commissure eDC IV. No projections are found in embryonic posterior commissures at this stage. b. Schematic summarizes the pattern of axonal projections from the w, x, y, z system of tracts into identified commisssural fascicles of the grasshopper at e50%. The pattern of projections is lineage specific. Projections from the w tract (dashed yellow) are hypothesized based on the known adult plan (see Boyan et al. 1993). c. Confocal image of the protocerebrum of Drosophila at E16 shows cells of the Z lineage (white) labeled by R9D11-Gal4>UAS-mcd8-GFP with axons (orange) in dorsal fascicles (according to body axis) of the primary brain commissure (com). Fascicles with axons that will contribute to the mature fan-shaped body are indicated (prFB). General label for neurons is via neurotactin/BP106 (cyan). d. As for c above but for cells of the Y lineage (white) with processes (orange) in dorsal fascicles of the primary brain commissure (com). e. Schematic summarizes the pattern of axonal projections from the w, x, y, z system of tracts into identified commisssural fascicles in the brain of Drosophila at E16. Each of the four lineages generates neurons that contribute to different commissural tracts. One tract (prFB), receiving axons from all four lineages, will become incorporated into the fan-shaped body. The other tracts are the embryonic precursors (e) of different commissures (ADC anterior dorsal commissure; ALC antennal lobe commissure; DPCC dorsoposterior commissure of central complex; LALC lateral accessory lobe commissure; SAC superior arch commissure; SEC supraellipsoid body commissure; SuEC subellipsoid body commissure; VPCC ventroposterior commissure of central complex). Scale bar represents 15μm in a, 20μm in c, d