Development of the Early Axon Scaffold in the Rostral Brain of the Small Spotted Cat Shark (Scyliorhinus canicula) Embryo

Figure 2

Development of axon tracts in the embryonic S. canicula brain. Lateral view of whole mount embryonic brain. Scale bars, 100 μm. (a) Stage 23, overview. The MLF neurones have projected well into the rhombencephalon. The scattered MLF neurone population has increased in size (unfilled arrow). The first neurones were present in the dorsal prosencephalon (arrow). (b)–(d) Stage 23, double labelled with Tuj1 (green) and HuC/D (red). (b) Neurones differentiated along the dorsal midline of the mesencephalon to give rise to the DTmesV (arrow). The MLF axon tract was well formed. (c) Three-four neurones appeared dorsally at the epiphysis (arrow). One neurone had projected its axon ventrally, almost reaching the MLF (arrowhead). This axon was a pioneer of the DVDT. Scattered MLF neurones were located rostrally to the initial MLF neurones (unfilled arrow). (d) Basal hypothalamus, where the TPOC neurones (nTPOC) differentiated. Scattered MLF neurones (unfilled arrow). ep: epiphysis; mes: mesencephalon; MLF: medial longitudinal fascicle; nTPOC: nucleus of the tract of the postoptic commissure; op: olfactory pit; pros: prosencephalon; III: oculomotor nerve.

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