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Leonardo Dutra Henriques, Paulo R Goulart, Julio C Oliveira, Daniela M O Bonci, Givago S Souza, Luiz Carlos L Silveira, Olavo F Galvão, Dora Fix Ventura; Opsin gene identification and evaluation of color vision in an albino capuchin monkey (Sapajus/Cebus sp). Invest. Ophthalmol. Vis. Sci. 2014;55(13):2364.
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© ARVO (1962-2015); The Authors (2016-present)
Albinism is characterized by a deficit of melanin production, leading to reduced or absent pigmentation of some organs. Anatomic differences described for an Old World Monkey include lack of fovea, high concentration of ganglion cells on the expected foveal area and higher crossing of visual pathways, but it was not clear how those differences would affect vision and specifically color vision. We investigated color discrimination in an albino capuchin monkey (Sapajus sp, formerly Cebus) using a modified version of the Cambridge Colour Test and compared it with healthy Sapajus data. Behavioral phenotypic characterization was compared with opsin gene genotype.
The animal was trained via positive reinforcement (190-mg banana pellet) to touch over an approximately square target (5cm2) on a pseudoisochromatic display, independently of hue and position and then exposed to the test condition. For the test target chromaticity varied along 20 equidistant vectors, with background chromaticity fixed at the achromatic point of the CIE 1976 diagram (u’= 0.1977, v’= 0.4689). Target chromaticity varied between 1100x10-4 and 20x10-4 u’v’ units along each vector, following a staircase procedure. The orientation of the best-fit ellipse generated for the 20 threshold points guided phenotypic characterization (Fig. 1). Exons 3 and 5 of the X-linked opsin genes were analysed in order to infer the spectral sensitivity of M/L cones.
The albino subject successfully learned the visual discrimination task, and produced color discrimination thresholds typical of deuteranopy (Fig. 2). The genetic analysis showed an SYT allele expressing an opsin with λ peak at 560-563nm, consistent with results described for other non-albino deuteranope Sapajus (Goulart et al., 2013).
There were no color vision or opsin gene differences between the albino variant and healthy deuteranopic subjects of Sapajus. Behavioral and genetic data obtained in this rare specimen will be complemented by ophthalmological and electrophysiological measures for a complete characterization of the animal's visual capabilities.
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