Boissin-Agasse L, Boissin J, Ortavant R
Biol Reprod. 1982 Feb;26(1):110-9. doi: 10.1095/biolreprod26.1.110.
Evidence of a circadian photosensitive phase in male mink, whose annual reproductive cycle is characterized by the recrudescence of testicular development in autumn, was based on the study of testicular response after interrupting the dark period by light breaks (0.5 h) offered at various times. In this mammal, the experimental short days 4L:20D and 8L:16D stimulated testicular growth. Short photoperiods, including a main light period of 3.5 h and an additional 0.5 h light break 7.5 h after the beginning of the main photoperiod, were as effective as 8L:16D in stimulating testicular development. On the other hand, when a 0.5 h light break occurred 11.5 or 15.5 h after the beginning of the main photoperiod, the same inhibiting effect on testicular activity was obtained as for long photoperiods. However, when 0.5 h light breaks were given 19.5 after the beginning of the main light period, some minks recognized, as "dawn", the onset of the shorter of the two light periods offered. Thus our results proved the existence of a special phase in the day cycle in which light inhibited testicular development in the mink which appears to be a short-day animal. One explanation of the difference between long-day and short-day animals would be the following: if for long-day animals exposure to light during the photosensitive phase led to gonadostimulation, in short-day mammals, like mink, it exerted an inhibiting influence on testicular growth.
雄性水貂的年度繁殖周期以秋季睾丸发育重新开始为特征，其昼夜光敏感阶段的证据基于对在不同时间通过短暂光照（0.5小时）打断黑暗期后睾丸反应的研究。在这种哺乳动物中，实验性短日照4L:20D和8L:16D刺激了睾丸生长。短光周期，包括3.5小时的主要光照期和主要光照期开始后7.5小时额外的0.5小时光照中断，在刺激睾丸发育方面与8L:16D一样有效。另一方面，当在主要光照期开始后11.5或15.5小时出现0.5小时的光照中断时，对睾丸活动产生了与长光周期相同的抑制作用。然而，当在主要光照期开始后19.5小时给予0.5小时的光照中断时，一些水貂将提供的两个较短光照期的开始识别为“黎明”。因此，我们的结果证明了在昼夜周期中存在一个特殊阶段，在这个阶段光照抑制了水貂的睾丸发育，水貂似乎是一种短日照动物。对长日照动物和短日照动物之间差异的一种解释如下：如果对于长日照动物来说，在光敏感阶段暴露于光照会导致性腺刺激，那么在短日照哺乳动物中，如水貂，光照会对睾丸生长产生抑制作用。
