At 31 (A–D) and 48 (E and F) hpf, mct8 morphants have fewer hindbrain and spinal cord neurons. A, Immunodetection of Zn8 in the hindbrain of 31-hpf wild-type zebrafish embryos microinjected with either CTRMO or MCT8MO. Arrowheads in A denote hindbrain interneurons, and red asterisks indicate trigeminal neurons. Scale bars, 50 μm. B, Expression of pax2a in 31-hpf wild-type zebrafish embryos microinjected with either CTRMO or MCT8MO. Black arrowheads indicate otic vesicle expression of pax2a. Scale bars, 100 μm. C, Immunodetection of acetylated β-tubulin in segments 4 to 10 of the spinal cord in 31-hpf wild-type zebrafish embryos microinjected with either CTRMO or MCT8MO. Scale bars, 50 μm. D, Expression of pax8 in 31-hpf wild-type zebrafish embryos microinjected with either CTRMO or MCT8MO. Arrows indicate first pax8-positive hindbrain interneurons. Scale bars, 50 μm. (e) Spinal cord expression of pax8 in 48-hpf wild-type zebrafish embryos microinjected with either CTRMO or MCT8MO. Scale bars, 200 μm. The boxed area in E corresponds to a higher-magnification image in F. Scale bars, 50 μm (F).