dlx1a and dlx2a are required for proper head outgrowth and arch cartilage patterning. (A–D) Lateral views of head morphology in 5-day-old larvae that received the (A) control MO, 0.5 mM; (B) dlx1aMO, 0.5 mM; (C) dlx2aMO, 0.25 mM; (D) an equal combination of dlx1aMO + dlx2aMO 0.25 mM each. (E–P) Cartilage elements stained with alcian blue. (E–H) are lateral views; (I–L) are ventral view. The inset in panel H is a lateral oblique view showing loss of the interhyal by fusion of hyosymplectic and ceratohyal elements (arrowhead). (M–P) Dissected ceratobranchial arch elements, numbered. cb, ceratobranchials; ch, ceratohyal; eth, ethmoid plate; hys, hyosymplectic; ih, interhyal; M, Meckel′s cartilage; pq, palatoquadrate. Arrows (A–D) indicate position of the mouth; asterisk in panel P indicates site of lateral branching. (A–P) Anterior is to the left. Scale bar in panel A: 250 µm; panels E and I: 100 μm; panel H inset, and M: 50 μm.