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. 2018 Aug 8;56(6-7):e23219. doi: 10.1002/dvg.23219

Figure 3.

Figure 3

(a) Adult quail and (b) duck heads in lateral view showing the mandibular adductor muscles that close the jaw (yellow dashed lines). The duck mandibular adductor inserts more laterally and proximally, and integrates into a pronounced coronoid process along the side of the lower jaw (black arrow) whereas the quail mandibular adductor inserts more dorsally and distally. Modified from Tokita and Schneider (2009). (c) Lateral view of cleared and stained quail and (d) duck embryos at stage 41. Cartilage is blue and bone is red. In duck, the coronoid process forms as a secondary cartilage (white arrow) on the lateral side of the surangular bone along the lower jaw skeleton. A corresponding cartilage is absent in quail (white asterisk). (e) In quck chimeras, jaw muscles come from the duck host whereas skeletal and connective tissues come from quail donor neural crest. Jaw anatomy on the donor side is transformed to something more like that found in quail. The mandibular adductor is narrower, inserts dorsally along the surangular, and as in quail, does not contain secondary cartilage. (f) In contrast, on the host side of quck, the mandibular adductor muscle is broader and inserts laterally on the surangular bone, and secondary cartilage forms within the insertion (white arrow) like that normally observed in duck. (g) Trichrome‐stained section of duck in lateral view showing the mandibular adductor muscle at its insertion (black arrow and stained purple), which is wide and triangular shaped along the surangular bone (stained blue). (h) On the host side of quck, the insertion looks the same as in duck whereas (i) on the donor side of quck (white asterisk) and in (j) quail the insertion is relatively thin. (k) Coincident with the eventual formation of secondary cartilage in duck but not quail, the chondrogenic transcription factor Sox9 is expressed highly in the insertion (white arrow) of duck and (l) on the host side of quck, but not in the insertion (m) on the donor side of quck (white asterisk) or (n) in quail. Modified from Solem et al. (2011)