Fig. 2. Developmental profiles of CHH- and MIH-expressing neurones during embryonic development. All confocal images are single sections, with the exception of D, which is a stacked and flattened projection image. (A) MIH-IR neurones at mid-eye development. Arrowhead, perikarya; arrow, sinus gland. Inset, higher magnification showing groups of four perikarya in each side of the developing eye. (B) CHH-IR neurones at mid-eye development. Note perikarya (arrowhead) and collaterals (arrow). Inset shows higher magnification of four perikarya. (C) Stacked (40• 1.5 µm), dual immunolabelled projection image of MIH (green, FITC) and CHH (red, Cy3) X-organ perikarya, axon tracts and sinus gland. Note that both peptides are not colocalised, but that the merged view through the sinus gland shows some areas of false colocalisation (yellow) due to processing of the image. (D) Expression of CHH in the pericardial organs at mid-eye development. Immunoreactive structures in the anterior and posterior bars of the pericardial organs are arrowed; sg, sinus gland, xo, X-organ. (E) Detail of the CHH-IR structures in the PO and adjacent areas during late eye development just prior to hatching. Note anastomoses between anterior and posterior bars (arrows; a,p), and five pairs of peripheral IR perikarya (left, small arrows). (F) View of posterior thorax and abdomen of a newly emerged zoea. Anterior and posterior bars of the pericardial organs are shown (a,p). Arrows show four small ventral peripheral thoracic perikarya (arrows) and segmentally iterated lateral abdominal perikarya (arrowheads) in lateral positions close to the anterior insertions of the abdominal flexor muscles. (G) Overview of CHH-IR structures in a newly emerged zoea. Arrows show the X-organ (xo), pericardial organs (po), and abdominal cells (ac). (H-K) Development of CHH-IR cells in the abdomen. (H) 4 days before hatching, (I) 2 days before hatching, (J) at hatching. Arrowheads in J show dorsal cells, which develop at this time, and appear to be close to the posterior insertions of the abdominal extensor muscles. Scale bars: 200 µm (A), 50 µm (B-F), 100 µm (G), 200 µm (H), 50 µm (I-K). Inserts (B,C): 10 µm.