Development and ultrastructure of <i>Drosophila</i> larval VNC.

<p>The development process of <i>Drosophila</i> larval VNC (<b>A–I</b>). VNC appearance and length are not significantly different in the periods of L1–2 (<b>A</b>), L1–12 (<b>B</b>), L1–22 (<b>C</b>) and L2–2 (<b>D</b>). The length of VNC in the L2–12 period (<b>E</b>) was longer than the L2–2 period (<b>D</b>), and once again with no obvious difference between L2–12 period and L2–22 period (<b>F</b>). The shape and the length of VNC display an obvious change during the L3–2 (<b>G</b>), L3–12 (<b>H</b>) and L3w (<b>I</b>) periods. White arrow indicates the brain, and black arrow indicates VNC. The ultrastructure of neuropils at low magnification in L1–2 period (<b>J</b>), L1–12 period (<b>K</b>) and L3w period (<b>L</b>). The VNC neuropil is wrapped by inner glial cells, and they were filled with nerve fibers and neurites (<b>J</b>–<b>L</b>). The size of neurites and neuropil in L1–2 period (<b>J</b>) are not obviously different than the L1–12 period (<b>K</b>), but size of neurites and neuropil in the L3w period (<b>K</b>) is bigger than L1–2 period (<b>J</b>) and L1–12 period (<b>K</b>). Most of the neurites are in S phase and T phase in L1–2 period (<b>J</b>) and L1–12 period (<b>K</b>). The black triangle indicates the neuronal soma, the white triangle indicates the inner glial cell and the thick arrow indicates nerve fiber. The large black box is enlarged from the small white box in the same diagram, and indicates the CV_I neurite. Scale Bar A–I: 50 µm; J–K: 5 µm; L: 10 µm.