Figure 1

The anterior arch mutants. A, C, E, G, I, K), morphology at 4dpf. B, D, F, H, J, L), flat mounted alcian blue stained pharyngeal cartilages. Red asterisks indicate the location of the joint between the M and PQ cartilages. Black asterisks indicate the joint between the CH and hyosymplectic cartilages. A, B) wild type. C, D) HM reduction mutant wom^hi2914. E, F) HM reduction allele sec61a^hi1058. G, H) HM reduction allele sec61a^hi2839B. I, J) anterior arch mutant csnk1a1^hi2069. M* and CH* are readily identified but dysmorphic. K, L) Meckel's and PQ reductions in mutant dys^hi3812. Most homozygous dys/dys animals show 'strong' reductions in the PQ such that only a posterior region of PQ is readily identifiable. M cartilage and the SY region are also strongly reduced. Joint fusion of the CH and HM region are also often present. M, N, O) Typically less than 5% of dys/dys animals show 'mild' reductions or joint fusions. M) Mild dys/dys animal showing only M-PQ and CH-HM joint fusions. N) Mild dys/dys animal showing intermediate PQ splitting in the presence of a well formed M that is fused to the anterior region of the PQ. O) Mild dys/dys animal showing complete PQ splitting but identifiable anterior and posterior PQ regions. The nos/foxI1 and laz/pbx4 mutants have been previously described and are therefore not shown.