Schleussner G, Gwinner E
Max-Planck-Institut für Verhaltensphysiologie, Erling-Andechs, Federal Republic of Germany.
Gen Comp Endocrinol. 1989 Jul;75(1):54-61. doi: 10.1016/0016-6480(89)90007-5.
Groups of photorefractory male European starlings have been kept under Nanda-Hamner LD schedules ranging from LD 6:6 to LD 6:54 for about 6 weeks. Subsequently, when transferred to LD 13:11, all birds of groups LD 6:18 and LD 6:42 went through a complete cycle of testicular growth and regression. Furthermore, they carried out a postnuptial molt, indicating that they have been able to terminate photorefractoriness under these LD schedules. In contrast, no positive responses could be detected in groups LD 6:6, LD 6:30, LD 6:36, and LD 6:54. Groups LD 6:12, LD 6:24, and LD 6:48 were intermediate in their reactions. Only part of these birds showed gonadal recrudescence when tested for photosensitivity. Changes in plasma testosterone levels were closely related to variations in testicular diameter. These results clearly suggest a strong circadian component in photoperiodic time measurement during the termination of photorefractoriness in the starling. Positive or negative responses were completely in line with predictions derived from the model of external coincidence. A comparison with the results of a similar experiment previously done with photosensitive birds failed to detect basic differences in the interpretation of the various LD cycles. These findings suggest that the same photoperiodic time measurement system is used at both phases of the starling's annual cycle.
将处于光不应期的雄性欧洲椋鸟分成几组，在光暗周期为6:6至6:54（小时）的南达-哈姆纳光暗周期条件下饲养约6周。随后，当转移到13:11的光暗周期时，光暗周期为6:18和6:42组的所有鸟类都经历了一个完整的睾丸生长和退化周期。此外，它们还进行了婚后换羽，这表明它们能够在这些光暗周期条件下终止光不应期。相比之下，在光暗周期为6:6、6:30、6:36和6:54的组中未检测到阳性反应。光暗周期为6:12、6:24和6:48的组反应处于中间状态。在测试光敏性时，这些鸟类中只有一部分出现性腺再发育。血浆睾酮水平的变化与睾丸直径的变化密切相关。这些结果清楚地表明，在椋鸟光不应期终止过程中，光周期时间测量存在强烈的昼夜节律成分。阳性或阴性反应完全符合外部符合模型得出的预测。与之前对光敏鸟类进行的类似实验结果进行比较，未能发现对各种光暗周期解释的基本差异。这些发现表明，在椋鸟年度周期的两个阶段都使用相同的光周期时间测量系统。
