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The site (intraocular vs. extraocular) of the biological clock driving a rhythm in melatonin content in the eyes of Japanese quail was investigated by alternately patching the left and right eyes of individual birds, otherwise held in constant light, for 12-hr periods. This patching protocol, therefore, exposed each eye to a light-dark cycle (LD 12:12) 180 degrees (12 hr) out of phase with the LD cycle experienced by the other eye. The optic nerves to both eyes were transected prior to initiating the patching protocol. The ocular melatonin rhythm (OMR) of the left eyes of quail could be entrained by this procedure 180 degrees out of phase with the rhythm expressed by the right eyes. Since optic nerve section would have deprived any putative extraocular clocks of photic entrainment information, the results show conclusively that the clock driving the OMR is located within the eye itself. In addition, the OMR of Japanese quail is remarkably unaffected by removing two potential neural inputs to the eye (sympathetic innervation from the superior cervical ganglia, and input from the isthmo-optic nucleus of the midbrain); this suggests that these inputs are not required to maintain the OMR. Finally, the clock driving the OMR of one eye does not appear to be coupled to the clock driving the OMR in the other eye, since permanently patching one eye abolished the ability of the patched eye to re-entrain to an 8-hr shift in the phase of an LD 12:12 cycle, whereas the exposed eye rapidly re-entrained to the phase-shifted cycle.

The quantitative relationship between cloacal gland size and testes weight during the stages of initial growth, involution and recrudescence is described. Cloacal gland foam was found to be a reliable indicator of testes size and function. The mean testes weight associated with the first presence of cloacal gland foam was 377 mg. and this occurred at a mean age of 29 days. The physical measurement of the cloacal gland provides a valuable noninvasive method of predicting testicular activity especially suited for long term experiments involving multiple measurements where a few coturnix may be used repeatedly (as their own control) rather than periodic killing of a large group of animals.

The single and combined effects of pinealectomy and bilateral ocular enucleation on sexual maturation and the photo-gonadal response of male and female coturnix (Japanese quail, Coturnix coturnix japonica) were studied. Observations were made on cloacal gland activity in males and rate of egg production in females. Immature males and females were exposed to short (6L:18D) photoperiods until sexually mature. Thereafter, a period of either short days (6L:18D) or total darkness was used alternately with long days (16L:8D) to induce gonadal regression or recrudescence, respectively. These alternating periods were continued until the birds were 59 weeks old.Neither the presence of the eyes nor the pineal gland were essential to gonadal maturation and function in the coturnix. Accelerated sexual maturity of males was observed after enucleation, and pinealectomy did not alter this response. Enucleated coturnix were resistant to photo-induced gonadal regression, and pinealectomy did not prevent this response. Thus, the eyes appeared to be necessary for the termination of egg production and cloacal gland activity due to shortened photoperiods. The data indicated an extraocular modification of the photo-induced gonadal activity but did not implicate the pineal as a functional mediator of these responses.