Sequence of development of the dorsal fin starting from hatching until the end of the larval period in Notopterus notopterus. (a) shortly after hatching, day 7, first mesenchyme condensation; (b) dorsal fin bud appears, day 8; (c) distinct dorsal fin bud and regression of embryonic fin fold, day 12; (d) well-developed dorsal fin anlage with 9 distinct radials and muscles, 7 fin rays, 17 days; (e) differentiated dorsal fin and regressed fin-fold of a stage 31 larva, 24 days; (f) dorsal fin in transition to a juvenile, 8–9 differentiated lepidotrichia, 36 days. Also note the progressive folding of myomeres and strengthening of myosepta; arrowhead points to developing dorsal fin. Scale bar = 2 mm.