Fig. 1. Creation and culture of avian chimeric mandibles. (A) To manipulate temporal information being conveyed between mesenchyme and epithelium, we exploited the divergent maturation rates of quail and duck embryos. Embryos were incubated until stage-matched at Hamburger-Hamilton (HH) 9.5. (B) Unilateral grafts of neural crest from the hindbrain (hb) and midbrain (mb) were transplanted between quail and duck. (C) Quail, duck and chimeras were harvested at various stages. (D) Mandibular primordia were surgically excised and cultured. (E) Quck mandibles contained quail donor mesenchyme (dark gray) alongside duck host mesenchyme (gray) and epithelium (light gray). (F) Skeletal structures derived from the mandibular primordia, visualized by Alizarin Red (bone) and Alcian Blue (cartilage) staining in actual (left) and schematic (right) dorsal view.