Fig. 4

Expression of axon guidance molecules. a–l Lv-netrin is expressed from 12 to 16 hpf in a ring in the vegetal plate (brackets in b–d). Lv-netrin turns on briefly in the apical organ (arrowhead in e). By 22 hpf, Lv-netrin is expressed in the edges of the oral ectoderm near the ciliary band. m–x Lv-semaa is expressed in a ring in the vegetal plate at 14 hpf (bracket in o). At 16 hpf, it is also expressed in the ventral ectoderm (arrowhead in p) and the apical organ. Through 32 hpf, Lv-semaa is expressed in the apical organ and the hindgut. Scale bars = 50um