| The morphological type, size, number and density of cells in the ganglion cell layer (GCL) were studied by Nissl-staining, retrograde cell degeneration with axotomy of the optic nerve, retrograde cell labeling of horseradish peroxidase (HRP) and carbocyanine dye (OiI) in the retina of Beijing duck (P1, P8 and P30). It will supply important foundation for elucidating the visual characteristic and special visual mechanism of the waterfowl-Beijing duck. The results were demonstrated as follows:1. The cells in the ganglion cell layer (GCL) were round, oval and polygon in somata. From the central retina to the peripheral zone, the cell size increased as large as 1.7-3.0 times (P8), but the cell density decreased to 36%~47% (P8). The center-peripheral graduation was significant in TP. The total number of cells (P30/P0=1.4) and their sizes (P30/P0=1.3) increased with age, but the cell density on average decreased (P30/P0=0.9).2. One high-density area of the RGCs was observed in the central retina(CA)(P0:8 860 cells/mm2; P8: 7 600 cells/mm2). From the central retina to the peripheral zone, the size of RGCs increased as large as 1.1 ~ 2.2 times (P8), but the cell density decreased to 42%~49% (P8). The center-peripheral graduation was significant in TP. The total number and average density of RGCs (P0:1.3\×106 cells, 5 370 cells/mm2; P8: 1.26×106 cells, 4 620 cells/mm2) decreased with age, but the size of cells increased from P0 (62.16 ±23.28 um2 in CA, 133.74±75.65 um2 in TP) to P8 (69.94±35.95 um2 in CA, 152.87±55.86 um2 in TP).3. According to all sizes of somal area and dentritic field and dentritic branching pattern, the RGCs of Beijing duck were classified into 4 types and 6 subtypes. Type I cells had small somal area (81.25±24.51um2) and dentritic field (14 446±8 702 um2). They were further subdivided into 2 subtypes of Is and Ic. Type II cells had medium-sized soma (201.17±65.99 um2) and dentritic field (60 167±16 896 um2), and contained 2 subtypes of IIs and IIc. Type III cells had medium-sized soma (251.67±90.05um2) and large dentritic field (156 329±43 693 um2), and only contained a subtype of IIIs.Type IV cells had large soma (471.20±72.31 um2) and dentritic field (189 320±42 438 um2), and only contained a subtype of IVc. The proportion of each subtype was28% (Is), 32% (Ic), 14% (IIs), 8% (IIc),13% (IIIs), 5% (IVc). In the central retina (CA), the proportion of small type RGCs was 77.2%, but the large dentritic field RGCs only 10.5% in the temporal periphery (TP). The large dentritic field RGCs (subtype IIIs) were much more than in the central retina of Beijing duck (about 25.4%).4. The dACs of Beijing duck were found in the ganglion cell layer of retina, which had round or oval somata and their somata were small (23.65±3.97 um2 on average). Their karyon were stained homogeneously by cresyl violet. The total number of these cells was 0.64×106 cells and accounted for 17~30% of total cells in GCL. The cell density was 1 720 cells/mm2 on average. However, one high-density area was observed in the central retina (CA, 3 860 cells/mm2). The cell densities in the temporal periphery (TP) and the nasal periphery (NP) were 1 780 cells/mm2 and 1 360 cells/mm2. These results indicated that the size of dACs was no significant difference in the centrality and periphery, but a center-peripheral graduation was detected in the cell density.
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