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. 2016 Jul 12;5:e15675. doi: 10.7554/eLife.15675

Figure 6. The spectral filtering of the C-type oil droplet is nearly optimal for color discrimination in bright light conditions.

Examples of the spectral sensitivity values of the LWS (red), MWS (green), SWS2 (blue) and SWS1 cones (purple) of (a) chicken (VS) and (b) zebra finch (UVS) used to model color discrimination. To find the optimal C-type oil droplet spectral filtering, we held all other values constant while varying droplet filtering over a wide range, resulting in shifts in the magnitude and wavelength of peak sensitivity of the SWS2 cone (gray lines). We then predicted the total number of colors that each of the hypothetical visual systems (c–d) could discriminate in bright (yellow lines), dim, (gray lines), and very dim light conditions (black lines). We repeated these analyses for a total of (e) 7 VS species and (f) 11 UVS species, and calculated total number of discriminable colors predicted for each C-type oil droplet λcut value under each of the three lighting conditions. The curves represent the mean ± S.D. total discriminable colors as a proportion of the model maximum for each lighting condition: bright (yellow lines), dim, (gray lines), and very dim conditions (black lines). The points above the curves are the observed λcut of the C-type droplets in each VS and UVS species and the predicted number of discriminable colors relative to the modeled optimum. (g) The mean ± S.D. increment spectral sensitivity of the visual systems of the VS species with the typical oil droplet configuration (solid line) or with mismatched C-type oil droplet filtering typical of UVS species (broken line). (h) The mean ± S.D. increment spectral sensitivity of the visual systems of the UVS species with the typical oil droplet configuration (solid line) or with mismatched C-type oil droplet filtering typical of VS species (broken line).

DOI: http://dx.doi.org/10.7554/eLife.15675.017

Figure 6—source data 1. The number of discriminable colors predicted using the receptor noise-limited model with species-specific ocular media transmittance, spectral sensitivity measures, and varying positions of the C-type oil droplet filtering cutoff.
The increment spectral sensitivity values calculated for the 11 UVS and 7 VS species with matched and mismatched C-type droplet filtering.
DOI: http://dx.doi.org/10.7554/eLife.15675.018
elife-15675-fig6-data1.xls (202KB, xls)
DOI: 10.7554/eLife.15675.018

Figure 6.

Figure 6—figure supplement 1. Color discrimination differs significantly between VS and UVS species and lighting conditions.

Figure 6—figure supplement 1.

The number of discriminable colors predicted for the actual visual system parameters of 7 VS and 11 UVS species in bright (open circles) and dim (black points) light conditions. The red and black lines indicate the mean values for each visual system in bright and dim light conditions, respectively. The p-values denote the statistical comparisons described in the text. N.S. indicates that there is no significant difference between the conditions.
DOI: http://dx.doi.org/10.7554/eLife.15675.019