Condensation morphogenesis is absent in dak-/- larvae. Pre-cartilage condensations in the first arch are larger in dak-/- larvae as judged by sox9a staining at 45hpf (A,B) and 50hpf (C,D). Individual cells within the condensation appear to have a more rounded morphology in dak-/- larvae than in wild-type larvae (compare arrows in C,D). Intercalation and flattening of chondrocytes to give rise to the ceratohyal cartilage in the second arch takes place between 54 and 58hpf in wild-type (E,G), but does not occur in dak-/- larvae (F,H). Chondrocytes begin to secrete cartilage matrix during this time as seen by Alcian Blue staining (G,H). Camera lucida drawings of chondrocytes in wild-type and dak-/- larvae (E′–H′). Scale bars = 10μM.
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