mef2cab1086 bone phenotypes and skeletal motion suggest a unique track of tissue orthogonal to the opercle. (A,B) Confocal projections of osteoblasts (sp7:EGFP) and bones (Alizarin Red) from live 6 dpf zebrafish. In A, the opercle (op) branchiostegal ray (br), cleithrum (c) and ceratobranchial 5 (cb5) bony elements are labeled and the eye, ear and mouth (m) are indicated for reference. In B, op and br bone phenotypes in wild types (WT), mef2cab1086 mutants with bone phenotypes resembling wild type (mef2cab1086 mild), and mutants with bony expansions (mef2cab1086 severe) are shown in this composite image. Arrows indicate a narrow track of extra bone. Images are projections of several confocal sections. (C) ‘Skeletonized’ time-lapse movies tracking the location and direction of ectopic growth (arrows). The major direction of op growth is along the y-axis. (D) Overlays of skeletonized time-lapse recordings from wild types and mutants. (E) Excerpts from a movie in which the head skeleton cartilage (sox9a:EGFP) and bone (sp7:EGFP) were imaged in the same fluorescent channel from a non-anesthetized larva and outlined (red). The same animal was imaged 0.1 s later and the head skeleton was outlined again (green) and overlaid on the first image revealing skeletal motion. All images are lateral views, anterior is towards the left and dorsal is upward in all panels. Scale bars: 100 µm.