FIGURE 2

FIGURE 2

FSNs have somas in the hindbrain and spinal cord. (A) Left panel: Brightfield and fluorescent merged image adjacent to myomeres one through five, indicating the distribution of the islet2B + somas (cyan) innervating the fin. The FSN somas innervating the fin are located dorsal to the dorsal root ganglion (DRG) neurons visible as clusters (asterisks). Fibers from DRGs also projected to the fin at this stage, but they cannot be traced individually. The lateral longitudinal fasciculus (LLF) extends from the hindbrain into the spinal cord. The transition area between myomeres three and four, historically referred to as the transition between the hindbrain and spinal cord, is indicated in orange. Cells posterior to the boundary are located in the spinal cord, and islet2B + cells in this location are Rohon-Beards. Right panel: Brightfield and fluorescent merged image of a dorsal view of a Tg[islet2B:GFP] fish. The hindbrain and spinal cord boundary is again marked in orange. The organization of the sensory neurons along the lateral margins of rhombomere 7/8 is bounded by the LLF. (B) All of the somas (cyan, left panel) are located posterior to the Mauthner neurons (red, M). Additionally, Mauthner neurons are notably more ventral (B′, M) in the hindbrain than the FSNs (B″, asterisk is DRG). Anterior is to the left, dorsal is up in (A left panel). Anterior is up, dorsal view in (A right panel and B). Scale is 40 microns in (A left panel) and 50 microns in (A right panel and B).