Pharyngeal arch and neurocranial cartilage patterns in wild-type and Hh-deficient zebrafish larvae. Alcian-stained cartilages were dissected and flat mounted; dorsal views are shown, anterior to the left. (a) The wild-type (WT) pharyngeal arches at 4.5 days postfertilization include: the mandibular arch (arch 1), containing Meckel's cartilage (m) and the palatoquadrate (pq); the hyoid arch (arch 2), containing the ceratohyal (ch) and hyosymplectic (hs); and five more posterior, branchial arches (3-7), each containing a ceratobranchial cartilage. (b) The wild-type neurocranium at 4.5 days postfertilization includes paired trabeculae (t) and an ethmoid plate (e). (c) Neurocranial defects in sonic hedgehog (shh) mutants. Trabecular cartilages fuse (arrows) at the midline. e, ethmoid; n, notochord; t, trabecula. Panels (b) and (c) taken from .