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Figure 4 | Zoological Letters

Figure 4

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

Figure 4

Developmental changes in the morphology and topography of coelomic cavities. (A) 3D-reconstructed stage-50 embryo of Eptatretus burgeri showing the position of the coelomic cavity (dark pink). Light pink indicates Tbx1/10A-positive myoblasts in pharyngeal arches. The coelomic cavity consists of the pericardium and peritoneal cavity, which are well defined and separate from each other at the caudal end of the pharynx. This morphology represents the generalized configuration of the coelomic cavity in vertebrate embryos. (B, C) Left lateral (B) and left caudal (C) views of a stage-53 embryo. Note that the junction between the pericardium (pc) and peritoneal cavity (pnc) corresponds to the level of the 10th pharyngeal pouch (p10) or the caudal end of the posteriorly shifted pharynx. (D) Parasagittal section showing the pharyngeal-pericardial region. (E) The same section as C at higher magnification. Note that the pronephros (pneph) is constantly found in the rostral part of the peritoneal cavity, and caudal to the pharynx. (F, G) Two transverse sections cut at the levels shown in B, reconstructed from serial parasagittal sections of the stage-53 embryo showing the pericardium (pc in E) and peritoneal cavity (pnc in F). (H) Reconstruction of a stage-53 E. burgeri embryo showing the developmental pattern of the venous system (purple). (I, J) Parasagittal sections of a stage-53 E. burgeri embryo (I) and a pre-hatching–stage E. atami embryo (J) showing the peribranchial venous system. Note that the venous system expands to form a sinus surrounding the gill pouches of the pre-hatching stage, just like a peribranchial coelom.

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