Pineal gland - pituitary (alpha-MSH) interrelationships in fur priming and reproductive cycles in mink (Mustela vison).

Our investigations show that blindness, either natural or surgically induced results in a lack of fur priming and sexual development. Definite genetic color phase differences were observed in the sensitivities of the biological clocks for initiating fur priming, testicular development and time of breeding and whelping. Finely-bred dark mink molted and their pelts primed later in the fall than did either pastel or opaline mink. Testicular development was earlier and more extensive for the opaline, but was intermediate for the pastels and slower and least extensive for the finely-bred dark mink. The dark mink, however, bred earlier than did either the pastel and opaline strains. Hedlund (deaf, white) mink pelted about the same time as the pastels and opalines, but they bred and whelped later than the above three strains of mink. Plasma alpha-MSH levels were inversely related to testosterone levels and testicular development. It was high in all three strains (darks, pastels and opalines) during both the spring and autumnal molts, but was low during testicular development and breeding.