Parapineal ablation eliminates laterotopic habenular efferent connectivity. (a-c) Dorsal views of the pineal complex at 3 dpf, visualized in Tg(flh:eGFP); Tg(foxD3:GFP) transgenic larvae, following laser ablation of parapineal precursor cells at 24–28 hpf. (a) Unablated control larva. (b) Failed ablation control larva, in which the parapineal has not been eliminated. (c) Parapineal-ablated larva, which lacks all parapineal cells. For clarity, pineal cells are pseudocolored blue and parapineal cells pseudocolored green. (a'-c') Three-dimensional reconstructions of habenular axon terminals in the IPN following lipophilic dye labeling of L (red) and R (green) habenular neurons. (a", b", c") Single-depth confocal images through the dorsal part of the IPN. (a"', b"', c"') Single-depth confocal images through the ventral part of the IPN. Following parapineal ablation there is an almost complete loss of L habenular innervation of the dIPN (c"). However, two small tufts of neuropil, containing both L- and R-sided axons, are consistently observed in the rostral dIPN (arrows in (c")). In parapineal-ablated larvae there is an increase in the density of L-sided axon terminals in the vIPN (compare (c"') to (a"') and (b"')). All panels show dorsal views, anterior top.