Distribution of rods and cones in the red-eared turtle retina (Trachemys scripta elegans)

Author(s)

Grotzner, Sonia Regina ^[1] ; de Farias Rocha, Fernando Allan ^{[2, 3]} ; Corredor, Vitor Henrique ^[4] ; Passos Liber, Andre Mauricio ^[4] ; Hamassaki, Dania Emi ^[5] ; Oliveira Bonci, Daniela Maria ^[4] ; Ventura, Dora Fix ^[4]

Affiliation

^[1] Univ Fed Parana, Dept Cell Biol, Curitiba, Parana - Brazil

^[2] Fed Univ Para, Inst Biol Sci, Belem, Para - Brazil

^[3] Fed Univ Para, Nucleus Theory & Res Behav, Belem, Para - Brazil

^[4] Univ Sao Paulo, Dept Expt Psychol, Sao Paulo, SP - Brazil

^[5] Univ Sao Paulo, Dept Cell & Dev Biol, Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF COMPARATIVE NEUROLOGY; v. 528, n. 9 DEC 2019.
• Web of Science Citations: 0

Abstract

We have identified the photoreceptors of Trachemys scripta elegans, an intensely studied species that is a model for color vision work. To recognize and count the different photoreceptor types, we labeled them with a combination of morphological and immunohistochemistry markers. The counts for the determination of the density of each photoreceptor type were made in wholemount retinas. The percentages found for each cone type were 29, 23, 21, 12, and 6%, respectively, for L (both types), double, M, S, and ultraviolet cones. The cones were found to be organized horizontally in a visual streak, a linear region with a higher density of photoreceptors that ends temporally in the periphery and more centrally in the nasal side. This region of high density of photoreceptors was not symmetrical along its extension; there was a region with conspicuous central density peaks in the temporal area, suggestive of an area centralis. We also observed a dorsoventral asymmetry in photoreceptor density, with greater density in the ventral region. This asymmetry was observed in cones and rods, but it was more pronounced in the rods. Our results corroborate and extend the findings of previous work in the literature describing the retinal photoreceptors of T. s. elegans and their spatial organization. The higher cone density within the visual streak reflects increased spatial resolution and its existence suggests the possibility of binocular vision. It is remarkable that within this region the entire potential for color vision is also present. (AU)

• FAPESP's process: 14/26818-2 - Development and implementation of visual evaluation methods: clinical applications and animal models
• Grantee: Dora Selma Fix Ventura
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 19/00777-1 - Relationship between circadian habits and visual functions in diurnal and nocturnal snakes (snakes, Colubridae)
• Grantee: André Maurício Passos Liber
• Support Opportunities: Scholarships in Brazil - Post-Doctoral