COMPARISON OF TOPOGRAPHICAL PATTERNS OF GANGLION AND PHOTORECEPTOR CELL-DIFFERENTIATION IN THE RETINA OF THE ZEBRAFISH, DANIO-RERIO

Earlier studies suggested retinal differentiation in the zebrafish com mences ventrally rather than centrally as is the case in other vertebr ates. Here we describe the topographical spread of cell differentiatio n for ganglion cells, double cones and rods in the zebrafish retina be tween 36 and 72 hours postfertilization (hpf), by using immunohistoche mical markers in retinal wholemounts. Staining for all three cell type s commenced within the ventral retina on the nasal side of the optic n erve and choroid fissure, at 38 hpf for ganglion cells and 50 hpf for double cones and rods. Within 3 to 4 hours, the staining of ganglion c ells and double cones spread in a continuous wave-like fashion into th e nasal region of the ventral retina. After this time, the staining pa tterns for ganglion cells and double cones progressed dorsally into th e central and temporal retina. Finally, stained somata of ganglion cel ls were observed within the temporal-ventral region by similar to 48 h pf, more than 8 hours later than the first ganglion cells within the n asal retina. The topographical spread of double cone staining was slig htly less orderly. After staining had extended into the nasal retina b etween 50 and 54 hpf, a small group of stained double cones often appe ared at the temporal edge of the choroid fissure by 56 hpf, simultaneo usly with initial staining observed dorsal and temporal to the optic n erve. The topographical spread of rod staining in the ventral retina w as more symmetrical. After rod staining appeared near the nasal edge o f the choroid fissure at 50 hpf, rods accumulated within a localized p atch nasal to the fissure. Approximately 5 hours after initial rod sta ining, scattered rod staining appeared on the temporal side of the cho roid fissure (similar to 55-57 hpf). Rods increased rapidly within the ventral retina, and a dense symmetrical patch extended out from the c horoid fissure into the nasal and temporal regions of the ventral reti na by 70 hpf. A scattered pattern of rod staining also occurred within the dorsal retina at this time. (C) 1996 Wiley-Liss, Inc.