Participation of the Eyes in the Photosexual Response of Japanese Quail (Coturnix coturnix japonica)

This study examined the role of the eye in the photosexual response with respect to the duration, wavelength, and intensity of light. Intact or blind juvenile, female Japanese quail were exposed to long (16L:8D), intermediate (12L:12D), and short (8L:16D) photoperiods of incandescent or fluorescent light, and the rate of sexual maturation was determined. Female Japanese quail matured on both long and short day-lengths, and blinding did not alter this response. The rate of sexual maturation (age at first egg) was proportional to the duration of the daylength. The onset of sexual maturation occurred later under both 8 and 12 h of incandescent than fluorescent light, and blinding prevented this response. Incandescent light was inhibitory to the rate of sexual maturation, and this effect involved the eye. Intact or blinded, juvenile, male Japanese quail were exposed to long photoperiods (16L:8D) of high and low intensity, and the rate of sexual maturation was determined. Subsequently, the rate of testicular regression of these birds was monitored following a short day (8L:16D) treatment. There was no difference in rate of sexual maturation between blinded and intact males on either high or low intensity lighting. However, exposure of adult males to short days resulted in complete testicular regression in intact males given high intensity light, whereas in intact males on low intensity light the testes only partially regressed. Testicular regression did not occur in any of the blinded birds. Although the eye was not essential for photostimulation and sexual development, in certain conditions it may act as a modifier of the photosexual response. However, the eye appears to be essential for short day-induced testicular regression of quail.