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Fig. 6 | EvoDevo

Fig. 6

From: Cartilage diversification and modularity drove the evolution of the ancestral vertebrate head skeleton

Fig. 6

Histology and histochemical properties of lamprey skeletal tissues. Scale bar is approximately 250 μm, and yellow lines indicate the estimated field of view in each panel. Black arrows correspond to hyaline cartilages whereas white arrows indicate mucocartilages. panels B-I are Toluidine Blue staining, panels J-M are Masson Trichrome staining, and panels N-Q are RGB staining. (A) Reference image for 40 dpf lamprey larva. (B) The tissues of the trabecular processes and the external velar bar contrast the features of hyaline and mucocartilage respectively. (C) The external velar bar is compared with features found in the medial flap, indicated by dotted lines. (D) The hyaline cartilages of the epibranchial bar, hypobranchial bar, and the branchial cartilages can be observed. (E) The hyaline cartilages of the parachordal process and the otic capsule are distinct from one another. (F,G) Cellular differences are observed between the mucocartilage of the medial flap and the external velar bar. (H,I) The histology of the ventromedial longitudinal bar is different from that seen in the mucocartilage of the ventrolateral plate and the endostilic cartilage. (J) The mucocartilage of the oral hood stands out in contrast to the adjacent connective tissues and muscle fibers. (K,L) Mucoartilages throughout the pharyngeal reason are largely ubiquitous. (M) The staining of the branchial cartilages is distinct from the adjacent mucocartilage. (N) Similar to Masson Trichrome, the mucocartilage of the oral hood is distinct from the adjacent dermis and muscle fibers. (O) Differences between the hyaline cartilages of the trabecular process and otic capsule are visible under RGB staining. (P) Differences between the internal and external components of the velum are minimal using RGB staining. (Q) Differences between the ventromedial longitudinal bar and the ventrolateral plate are minimal using RGB staining. Keywords: ba: branchial arches; ebb: epibranchial bar; ec: endostilic cartilage; evb: external velar bar; hbb: hypobranchial bar; hy: hyoid; ivb: internal velar bar; lb: lateral bar; mf: medial flap; oc: otic capsule; oh: oral hood; op: oral papilla; pr: parachordal process; so: subotic mucocartilage; tr: trabecular process; vlp: ventrolateral plate; vmlb: ventromedial longitudinal bar

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