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Figure 3 | Zoological Letters

Figure 3

From: On the peculiar morphology and development of the hypoglossal, glossopharyngeal and vagus nerves and hypobranchial muscles in the hagfish

Figure 3

Mid to late pharyngular-stage embryos of Eptatretus burgeri . (A–C) Dorsal views of embryos at stages 45, 50, and 53, with the brain and notochord made transparent mainly to visualize the relative positions between pharynx (yellow), otic vesicle (ot) and somites. Dorsal root ganglia of spinal nerves (sp) are shown in orange, medial to the somites. (D–F) Development of the peripheral nerves in the same embryo as shown in A–C. Cranial nerves are shown by different colors. In this reconstruction, the glossopharyngeal and vagus nerves (green) are not always easy to distinguish from each other. Note that, as with the development of the somites, the spinal nerves first arise caudal to the pharynx and later shift rostrally to the mid-otic level at stage 53. (G, H) Reconstructions of the spinal nerves in the head (originally the right side) (G) and rostral part the body (head and pharynx; H) of a pre-hatching–stage E. atami embryo. Spinal nerves are colored orange. Note that in the head the rostral spinal nerves (putative occipitospinal nerves) pass superficial to the branchiomeric nerves, as does the hypoglossal nerve in other vertebrates.

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