Figure 1.
Methods used for measurement of male red coloration and female red sensitivity.
(A) Color tetrahedron based on stickleback spectral sensitivity functions with each of the four corner points representing the exclusive excitation of a single cone (UV, S, M, L). The three independent coordinates x, y and z define the position of a spectral color in the three-dimensional space. Chromaticity was determined as the distance between a measured color point (orange dot) and the achromatic origin (grey dot) and represents the degree of chromatic difference between both locations. (B) Schematic representation of the optomotor setup used to measure visual sensitivity of female threespine sticklebacks. Test fish were exposed to a rotating stimulus pattern under three different stimulus wavelengths in the orange-red spectral region (590, 610 and 630 nm) generated by interference filters. To determine threshold sensitivity levels light intensity was increased in five steps by using a series of ND filters (see text for details).
Figure 2.
Spectral data on male red coloration and female red sensitivity.
(A) Spectral reflectance for the cheek region of 25 reproductively active males. Plotted is the mean of the reflectance intensities (black line) ± standard deviation of the mean (shaded area). Reflectance was measured relative to a 98% white reference standard. (B) Mean relative sensitivity of daughters at three wavelengths of long-wave light (590, 610 and 630 nm) as measured in optomotor response tests. Error bars indicate standard deviation of the mean.
Figure 3.
Comparison between red color expression in fathers and the red sensitivity of their daughters (n = 25).
Relationship between daughters' relative sensitivity at 590 nm and fathers' (A) red chroma (after negative reciprocal transformation) and (B) chromaticity, respectively. The lines are the least square regressions [(A): Y = 0.413x+1.897, R2 = 0.547, F = 27.80, P<0.0001; (B): Y = 3.997x−0.211, R2 = 0.373, F = 13.70, P<0.01].