title: The topography of cone photoreceptors in the retina of a diurnal rodent, the agouti (Dasyprocta aguti).
abstract: The presence, density distribution, and mosaic regularity of cone types were studied in the retina of the diurnal agouti, Dasyprocta aguti. Longwave-sensitive (L-) and shortwave-sensitive (S-) cones were detected by antibodies against the respective cone opsins. L- and S-cones were found to represent around 90 and 10% of the cone population, respectively. There was no evidence for L- and S-opsin coexpression in agouti cones. L-cone densities were highest, up to 14,000/mm2, along a horizontal visual streak located about 2-3 mm dorsal to the optic nerve, and the L-cone distribution showed a dorsoventral asymmetry with higher densities in ventral (about 10,000/mm2) than in dorsal (about 4000/mm2) retinal regions. This L-cone topography parallels the agouti's ganglion cell topography. S-cones had a peak density of 1500-2000/mm2 in the central retinal region but did not form a visual streak. Their distribution also showed a dorsoventral asymmetry with densities around 600/mm2 in dorsal and around 1000/mm2 in ventral retinal regions. The patterning of cone arrays was assessed by the density recovery profile analysis. At all eccentricities evaluated, the S-cone mosaic less efficiently packed than the L-cone mosaic. Rod densities ranged from 47,000/mm2 in peripheral to 64,000/mm2 in central retina, and rod:cone ratios were 4:1-9:1. The comparatively low rod density and high cone proportion appear well adapted to the diurnal lifestyle of the agouti.
authors.affiliation: Departamento de Fisiologia, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil. rochaf@ufpa.br
authors.forename: Fernando Allan de Farias
authors.initials: FA
authors.lastname: Rocha
authors.forename: Peter K
authors.initials: PK
authors.lastname: Ahnelt
authors.forename: Leo
authors.initials: L
authors.lastname: Peichl
authors.forename: Cézar A
authors.initials: CA
authors.lastname: Saito
authors.forename: Luiz Carlos L
authors.initials: LC
authors.lastname: Silveira
authors.forename: Silene Maria A
authors.initials: SM
authors.lastname: De Lima
mesh_terms: D000818:Animals; D002452:Cell Count; D055253:Color Vision; D055358:Cone Opsins / Q000096:biosynthesis / Q000648:ultrastructure; D007150:Immunohistochemistry; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology* / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000166:cytology; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000378:metabolism; D017299:Rod Opsins / Q000096:biosynthesis / Q000648:ultrastructure; D012377:Rodentia
chemical_list: D055358:Cone Opsins; D017299:Rod Opsins