Fig. 3. Developmental profiles of neurones immunoreactive to PDH during embryonic development. All images are stacked flattened projection images (20-40 1 µm slices) (A) PDH-IR neurones 1-2 days after eye anlage formation, five pairs of perikarya can be seen. (B) PDH-IR neurones 2-3 days after eye anlage formation. Note two pairs of anterior-median brain neurones and groups of 2, 4 and 5 perikarya in the eye neuropil. (C) PDH-IR neurones 7-8 days after eye anlage formation. Note that only one pair of anterior-median protocerebral neurones is now evident (arrows) and that single immunoreactive neurones appear in the posterior region of the tritocerebrum (small arrows). (D) PDH-IR neurones in the eye neuropil of a fully developed embryo. Note axons entering and leaving the sinus gland (sg, arrows), and development of a prominent plexus in the lamina ganglionaris (lg). Perikarya numbers (11) remain unchanged. (E) PDH-IR structures 7-8 days after eye anlage formation. Perikarya marked with small arrows correspond to those in C. Note the immunoreactive neurones possibly projecting to the stomatogastric ganglion (arrow), which originate from a small IR structure in the circumoesophageal connectives (arrowheads) Small arrows point to arborising (possibly segmentally iterated) dendrites in the thorax. Abbreviations: lg, lamina ganglionaris; oe, oesophagus; sg, sinus gland. Scale bars: 50 µm.