Effects of low intensity red light on testicular recrudescence in Japanese quail

Experiments were conducted to determine if sighted and blind plumage color mutants of Japanese quail elicit comparable testicular recrudescence when exposed to long daily photoperiods of low intensity red light. Quail exhibiting testicular regression after exposure to 8 hr of light daily for several weeks were blinded via bilateral ocular enucleation. A control group was not enucleated. Two light intensities, 1.4 and 2.8 lx, were applied to half of the birds in each group during a 16 hr daily photoperiod for several weeks. Enucleated birds and birds under the 2.8 lx intensity had greater testis weights than the controls. Birds were also blinded by optic tract sectioning, and a .7 lx red light intensity treatment was included. Greater testis weights were found in birds under higher light intensities. Three plumage pigmentation mutants, sex linked incomplete albino, white and wild-type, were exposed to 8 hr of light daily for either 4 or 8 weeks to induce testicular regression. They were then exposed to the three light intensities for 3 weeks. Higher intensities and albinism resulted in greater testicular recrudescence only when the regression interval was 8 weeks, even though testicular regression appeared after 4 weeks. The absence of eyes or plumage pigmentation, resulting in an increased exposure of the encephalon for extraretinal light reception, may have effected greater testicular recrudescence. Severed optic tracts with tract eyes did not produce this response to light, indicating that the eyes may play a role in mediating the photosexual reflex in quail. Lower intensities may have resulted in reduced tissue penetration and testicular growth. A definite threshold intensity necessary to elicit testis growth was not found.