Female preference for colour-enhanced males: a test of the sensory bias model in medaka, a drab fish

Sexual selection research has long focused on the evolution of female mate preferences. Most of the models that have been developed posit that mate preferences evolve in a mating context. In contrast, the sensory bias model proposes that mate choice preferences arise in a non-mating context, as a by-product of natural selection acting on a female’s perceptual system. Recent research has shown that many species of fishes, from across a large clade including poeciliids, goodeids, and medaka, have a bias for long wavelength (LW) colors (yellow, orange, red) in a non-mating context. Even species that do not have LW-colored ornaments, apparently because they have been lost secondarily, retain this latent bias for LW colors. Here, we predicted that female Oryzias latipes (Japanese medaka), a drab species with a latent preference for LW colors, would show a mate choice preference for males with an artificial secondary sexual trait—a colored stripe added to their flank. We confirmed that female...