Fig. 4.
Some secondary lineages acquire additional branches during metamorphosis. (A) Schematic illustrating that a fully extended SAT can produce an off-shoot (SATlate) during metamorphosis, presumably generated by late-born secondary neurons that had not yet produced axonal fibers during larval development. The addition of branches does not affect the overall morphology of the main SAT. ((B) and (C)) Z-projections of confocal sections of brain hemispheres containing BAmv1-MARCM clones (fixed at larval stages in (B); at adult stages in (C)). BAmv1 has two HSATs, a dorsally-directed HSATd and posteriorly-directed HSATp by the L3 stage. In the adult, a third branch, SATlate, is added to HSATd, and extends laterally into the VLPa compartment (neuropil is labeled by anti-DN-cadherin). ((D)–(F)) Z-projections of representative confocal sections of BP106/BP104-labeled pupal brains, highlighting the emergence of the SATlate lateral branch, appearing between st. P24 (data not shown) and P32 (E). Of note, the collateral branch formed during metamorphosis follows a novel trajectory different from other SATs formed by the lineage during larval development. Scale bars: 50 μm ((B)–(G)) and 10 μm ((D)–(F)). Other abbreviations: cell body cluster CC.