Loss of mesendoderm and fgf8 or fgf3 disrupts otic induction. Lateral views (anterior to left) of otic vesicles in live embryos at 35 hpf. A: Wild-type control. B: Wild-type embryo treated with 100 μM SB431542. C:fgf8-/- mutant. D,E:fgf8-/- mutants treated with 100 μM SB431542 showing either a micro-vesicle (D, arrow) or no morphologically detectable vesicle (E, asterisk). F:fgf3-morphant embryo treated with 100 μM SB431542 showing no morphologically detectable otic vesicle (asterisk). Scale bar = 25 μm.