Figure 1 – A graph showing the ranges of wavelength detection by the optic cells
Colour vision is a process involving the translation of the wavelength composition of a stimulus into information an organism. It can guide behaviour, and involves photoreceptors of the eye and opsin proteins.
Photoreceptors are composed of two components, one of which is the visual pigment, which is covalently linked to the second component, a chromophore. In primates this chromophore is 11-cis-retinal and is a derivative of vitamin A1. Primate colour vision systems involve two types of photoreceptor cell; rod cells and cone cells.
Rod cells are used for monochrome vision in low light conditions, while cone cells are important for colour vision in higher light conditions, such as daylight and room light levels.
Different primates have different numbers and combinations of visual pigments, which results in great variation amongst primates in their colour vision capabilities.
Lemurs' colour vision appears to differ greatly than that of its closer relatives, possibly explained by the early convergence of lemurs from the rest of the primate phylogeny (Figure 2).
Due to this early divergence, lemurs were established as a family for a long time evolutionarily. All lemurs are native to Madagascar and so their environment is relatively similar.
The numbers of opsin proteins present in each lemur genus along with the activity pattern of each genus (nocturnality vs diurnality) were found.
The results are shown in figure 3. Notably the Brown and Ringtailed lemurs can adopt both a nocturnal and diurnal lifestyle, and nearly all lemurs lack any colour vision for the wavelength associated with red.
A future implication of this work is to study lemurs in captivity to examine whether their living conditions have an impact on their colour vision, and the ethical implications associated with this.
School of Mathematical Sciences, University of NottinghamUniversity Park NG7 2RD
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