Dixit Anand S, Singh Namram S, Bamon Iadalangki
Department of Zoology, North-Eastern Hill University, Shillong-793022, Meghalaya, India.
Department of Zoology, Cotton University, Guwahati-781001, India.
Photochem Photobiol Sci. 2017 Jul 1;16(7):1146-1152. doi: 10.1039/c6pp00271d. Epub 2017 Jun 7.
Experiments were performed on the subtropical tree sparrow (Passer montanus) to investigate the involvement of an endogenous circadian rhythm in photoperiodic time measurement during the initiation of gonadal growth and functions and also to study the photic entrainment of the circadian activity rhythm. Groups of photosensitive birds of both sexes were exposed to different "night-interruption" light-dark regimes of 24 h duration viz., G1 - 6L/5D/1L/12D, G2 - 6L/6D/1L/11D, G3 - 6L/7D/1L/10D, G4 - 6L/8D/1L/9D, G5 - 6L/10D/1L/7D, G6 - 6L/12D/1L/5D, G7 - 6L/14D/1L/3D and G8 - 6L/16D/1L/1D for 30 days in which 17 h long nights were interrupted by 1 h light pulse falling at different ZTs (i.e., 11, 12, 13, 14, 16, 18, 20 and 22). A control group, for each sex, was maintained under 7L/17D. The birds of all groups behaved as though they had been exposed to a stimulatory photoperiod except those of G1, G8 and the control. Furthermore, the serum levels of testosterone in males and estradiol-17β in females ran almost parallel to changes in the gonadal size. Birds, when exposed to 12L/12D, showed entrainment of their locomotor activity rhythm with the activity confined mainly during the light phase. However, various characteristics of the activity rhythm differed significantly upon transfer of birds to various night interruption regimes. These results suggest the involvement of the endogenous circadian rhythm in photoperiodic time measurement during the induction of gonadal growth and functions in the tree sparrow. Also, there is photic entrainment of the locomotor activity rhythm that shows variations in various circadian characteristics under different night interruption cycles suggesting that the photoinducible phase is differentially sensitive to light.
以亚热带树麻雀（Passer montanus）为实验对象，研究内源性昼夜节律在性腺生长和功能启动过程中的光周期时间测量中的作用，并研究昼夜活动节律的光诱导。将不同性别的光敏鸟分组，暴露于24小时时长的不同“夜间中断”明暗周期，即G1 - 6小时光照/5小时黑暗/1小时光照/12小时黑暗、G2 - 6小时光照/6小时黑暗/1小时光照/11小时黑暗、G3 - 6小时光照/7小时黑暗/1小时光照/10小时黑暗、G4 - 6小时光照/8小时黑暗/1小时光照/9小时黑暗、G5 - 6小时光照/10小时黑暗/1小时光照/7小时黑暗、G6 - 6小时光照/12小时黑暗/1小时光照/5小时黑暗、G7 - 6小时光照/14小时黑暗/1小时光照/3小时黑暗和G8 - 6小时光照/16小时黑暗/1小时光照/1小时黑暗，持续30天，其中17小时长的夜间被在不同时间（即11、12、13、14、16、18、20和22）落下的1小时光脉冲中断。每个性别设置一个对照组，维持在7小时光照/17小时黑暗条件下。除G1、G8组和对照组外，所有组的鸟表现得就好像它们暴露于刺激性光周期一样。此外，雄性的睾酮血清水平和雌性的雌二醇-17β血清水平几乎与性腺大小的变化平行。当鸟暴露于12小时光照/12小时黑暗时，其运动活动节律出现诱导，活动主要局限于光照阶段。然而，将鸟转移到各种夜间中断周期后，活动节律的各种特征有显著差异。这些结果表明内源性昼夜节律参与树麻雀性腺生长和功能诱导过程中的光周期时间测量。此外，运动活动节律存在光诱导，在不同的夜间中断周期下，其各种昼夜特征表现出变化，这表明光诱导阶段对光的敏感性不同。
