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21 hpf Development

[ Back to Pharyngeal development: Pre-skeletal]

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21 hpf
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By 514 hpf, growth of the bony elements of the pharyngeal skeleton have almost completely engulfed cartilage elements and also expanded across the ventral portion of the gills. Elements shown here include Meckel’s (Mk), palatoquadrate (pq), basihyal (bh), ceratohyal (ch), interhyal (ih), and hyosymplectic (hs) cartilages, and premaxilla (pm), maxilla (mx), dentary (d), anguloarticular (aa), retroarticular (ra), quadrate (q), ventral hypohyal (hhv), ceratohyal bone (chb), branchiostegal rays 1-3 (bsr1, 2, 3), urohyal (uh), symplectic (sy), preopercle (pop), interopercle (iop), subopercle (sop), and opercle (op) bones. Becoming visible here between 14 dpf and 21 dpf are the infraorbital 1 (inf1) and metapterygoid (mpt) bones, likely derived from the first pharyngeal arch, and the epihyal (eh) bone, derived from the second pharyngeal arch. Also visible are the scleral (sc) cartilage of the eye and the cleithrum (cl) bone of the pectoral fin skeleton.