Fig. 10

Fig. 10 Retinal development between 72 and 96 hpf. The left column shows sections from 72 hpf fish, the right from 96 hpf fish. Each horizontal pair of photos (a and b, c and d, etc.) have the same magnification, given by the scale bar on the right. (a, b) Transverse sections through the heads passing through the centers of the eyes. Dorsal is up. The brain (B), mouth (M), retina (R), and lens (L) are indicated. The boxes labeled e and f indicate the regions shown in e and f. (c, d) More highly magnified views of the eyes in the preceding micrographs. The various layers are indicated: pigmented epithelium (PE), outer nuclear layer (ONL), outer plexiform layer (OPL), inner nuclear layer (INL), inner plexiform layer (IPL), ganglion cell layer (GCL), and optic fiber layer (OFL). The older eye is larger and slightly more developed. The dark lines indicate the boundaries of the functional retina, the sector containing both plexiform layers and photoreceptor outer segments. Lateral to the functional retina lie the lens, the iris (I), and the retinal germinal zone (GZ). (e, f) More highly magnified views (see boxes in a and b) showing the outer segments (brackets) and the medial rectus muscle (MR) enveloped by dashed lines. In the older fish, the outer segments are longer and the medial rectus is larger and has more myofibrils (e.g., curved arrows). (g, h) Tangential sections through the outer nuclear layer of the nasal retina, showing the transversely cut cone nuclei (Nu) in the central field of both panels and the inner segments (IS) in the surrounding area.