Dixit Anand S, Singh Namram S
Department of Zoology, North-Eastern Hill University, Shillong 793022, Meghalaya, India.
Department of Zoology, Cotton College State University, Guwahati 781001, India.
J Photochem Photobiol B. 2016 May;158:61-8. doi: 10.1016/j.jphotobiol.2016.02.014. Epub 2016 Feb 26.
Seasonality in daily locomotor activity pattern was investigated in the subtropical tree sparrow by exposing a group of birds to natural day lengths (NDL) for 30days and another group to 12L/12D for 14days followed by transfer to constant dim light (LLdim) for another 15days in four different seasons of the year. Serum testosterone levels were also measured during different seasons. Sparrows, under NDL, exhibited distinct circadian rhythmicity in their locomotor activity with almost similar general pattern in different seasons that restricted mainly to the light hours. However, they showed season-dependent differences in the characteristics of circadian locomotor activity rhythm. Birds, when exposed to 12L/12D, showed entrainment of their locomotor activity rhythm with the activity confined mainly during the light phase. Though, tau (τ) under free run conditions did not show any significant difference, the activity period varied significantly in different seasons. The highest level of testosterone was recorded in the spring season that corresponded with the maximum locomotor activity in spring months. The seasonality in daily locomotor activity correlates with the seasonal changes in testosterone levels suggesting the influence of gonadal steroids on endogenous circadian system which is indicative of adaptation of tree sparrow to local photoperiodic conditions.
通过在一年的四个不同季节里，将一组麻雀暴露于自然日长（NDL）30天，另一组暴露于12小时光照/12小时黑暗（12L/12D）14天，随后再转移到持续昏暗光照（LLdim）下15天，研究了亚热带树麻雀日常运动活动模式的季节性变化。同时还测量了不同季节的血清睾酮水平。在自然日长条件下，麻雀的运动活动表现出明显的昼夜节律，不同季节的总体模式几乎相似，主要局限于光照时间。然而，它们在昼夜运动活动节律特征上表现出季节依赖性差异。当麻雀暴露于12L/12D条件下时，其运动活动节律会与光照同步，活动主要局限于光照阶段。虽然在自由运行条件下，昼夜节律周期（τ）没有显示出任何显著差异，但不同季节的活动期有显著变化。春季记录到的睾酮水平最高，这与春季月份的最大运动活动相对应。日常运动活动的季节性变化与睾酮水平的季节性变化相关，表明性腺类固醇对内源性昼夜节律系统有影响，这表明树麻雀对当地光周期条件的适应性。
