Fig 1.

A. Serotonin immunostaining of an embryonic lobster brain at hatching. Each dorsal giant neuron (DGN) innervates the ipsilateral olfactory (OL) and accessory (AL) lobe. The intense labeling of the OL and AL is due to the massive DGN projection to these areas. B. Following a 6-hour survival time after BrdU injection, labeled nuclei (red) are found in the lateral proliferation zone (LPZ) immediately adjacent to the AL. Serotonin antibodies label a group of fibers (green; arrowheads) that terminate blindly at the proliferation zone. These fibers have been traced back to the DGN in the adult, juvenile, and larval brains (adapted from Beltz et al., 2001). C. Stacked confocal images illustrate the morphology of normal OL (Ci) when these late embryos are chemically depleted of serotonin. The cells were filled intracellularly with Lucifer Yellow. The arrow in C points to the primary neurite that courses anteriorly to innervate target regions in the medulla terminalis (adapted from Sullivan et al., 2000). Scale bars: A= 200 μm. B, C = 20 μm.