Visual pigments and oil droplets in genetically manipulated and carotenoid deprived quail: a microspectrophotometric study.

The spectral absorbances of visual pigments and retinal oil droplets were studied in three groups of Japanese quail (Coturnix coturnix japonica): an unselected control population and two artificially selected strains that exhibited different early approach preferences between blue and red stimuli. The oil droplets were examined with and without prior carotenoid deprivation. Four cone pigments and five oil droplet types were identified, resembling those in other avian species. Carotenoid deprivation eliminated all pigmentation detectable in oil droplets by microspectrophotometry. Placement of chicks on normal diet gradually reintroduced normal pigmentation within the span of about a week. No statistically significant differences were found between normal and genetically selected birds in either visual pigments or oil droplet types, or in their relative proportions. It is concluded that differences in the early colour preferences of quail are unlikely to be a result of variation in the spectral properties of their photoreceptors.