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Fig. 3 Jaw and pharyngeal cartilage defects in low mutants and in larvae injected with ap2bMO. Lateral views (A-D) of live larvae show reduced head size and jaw defects (arrows) in AP2-deficient animals at 4 dpf. (E-H) Dissected pharyngeal cartilages from 4 dpf shown in ventral view. Pharyngeal cartilages are absent or reduced in all but the mandibular arch in low mutants (F), and fuse with the anterior basicranial commissure of the skull. The neurocranium (asterisks) is typically not affected. (G) Injection of ap2bMO alone has no effect, but injection into low (H) causes loss of both pharyngeal and neurocranial cartilage. The posterior neurocranium remains intact. cb, ceratobranchial; ch, ceratohyal; hs, hyosymplectic; m, Meckel′s cartilage; n, notochord; pc, parachordals; pq, palatoquadrate. Scale bars: 100 µm.