Fig. 3

Fig. 3 Apoptosis in sensory organs. (A–C) Olfactory organ. (A, B) Transverse sections of 36- (A) and 48-hpf (B) embryos; dorsal is up and lateral is right. (C) Whole-mount of 36-hpf embryo; rostral is left and dorsal is up. (A) The anterior surface of the olfactory organ contains numerous apoptotic cells at 36 hpf. (B) At 48 hpf, the morphology and location of apoptotic cells in intermediate layers suggest that they are dying neurons. Apoptosis is also seen at the margin of the telencephalon, in the prospective olfactory bulb region (arrows). (C) Lateral view of the head at 36 hpf demonstrates clusters of dying cells in the rostral olfactory organ (dotted lines). (D–F) Eye. (D) Whole-mount lateral view of eye at 24 hpf shows large numbers of apoptotic cells in the lens and scattered apoptotic cells in the retina at this age. Rostral is left and dorsal is up. (E) Transverse section at 24 hpf demonstrates that the majority of the apoptotic cells in the lens are at the outer margin, while the retina contains few apoptotic cells (arrow). Lateral is left and dorsal is up. (F) Transverse sectin at 36 hpf reveals numerous apoptotic cells in the retina at various levels and fewer apoptotic cells in the lens than seen at 24 hpf (compare to E). Lateral is left and dorsal is up. (G, H) Neuromasts of trunk lateral line organs. (G) Horizontal section of 36-hpf embryo, showing apoptotic cells within lateral line organs on outer surface of trunk (arrows). (H) Lateral view of single lateral line organ in 72-hpf whole mount; large apoptotic cells are clustered in the central region of the organ. Asterisk indicates pigment cells. Dorsal is up. (I) Apoptotic Rohon–Beard neurons (arrowheads) in a horizontal section of the dorsal spinal cord of a 48-hpf embryo. Rostral is up. Abbreviations: myo, myotome; noto, notochord; oo, olfactory organ; tel, telencephalon. Scale bars, 25 μm for all panels.