Department of Zoology, University of Lucknow, Lucknow, India.
Department of Physiology, King Georges Medical University, Lucknow, India.
Neuroendocrinology. 2024;114(11):993-1004. doi: 10.1159/000540394. Epub 2024 Jul 25.
Light is the primary source of energy and regulates seasonal changes in physiology and behavior. The role of photoperiod has been much investigated in several bird species, but the role of illumination in seasonal adaptations of passerine finches is less understood. We, therefore, investigated the effects of photoperiod and illuminance on migratory physiology in a Palearctic-Indian migratory finch, redheaded bunting (Emberiza bruncieps).
Photosensitive buntings maintained under short days (8L:16D) were divided into three groups receiving 5, 25, and 100 lux of white daytime illuminance, respectively. Thereafter, using photoperiodic manipulation three life history states, i.e., nonmigratory (NM), premigratory (PM), and migratory (MIG) states were induced in the buntings. The birds in the MIG state were consecutively perfused after seven nights of Zugunruhe (nighttime migratory restlessness) for neuropeptide Y (NPY)-immunohistochemistry, which is involved in a wide range of functions including energy homeostasis, vision, and fat deposition in birds.
We found differential effects of illuminance on locomotor activity and physiology. Photostimulated birds showed intense nighttime activity in the MIG state. We observed premigratory hyperphagia in the birds, with increased food intake in the 100 lux group, which was reflected in the body mass gain in the MIG state. NPY expression on the periphery of the nucleus rotundus suggests its potential role in visual acuity, where the NPY-cell count significantly decreased under 25 lux illumination.
We demonstrate that migrating birds may also experience physiological effects from changes in daytime illumination. We observed illuminance-dependent variations in the quantity of food consumed by the birds. It indicates that the illuminance may also impact the encephalic centers that control food intake.
光是能量的主要来源，调节着生理和行为的季节性变化。光周期在几种鸟类中的作用已经得到了广泛的研究，但光在雀形目雀类季节性适应中的作用还不太清楚。因此，我们研究了光周期和光照度对北极-印度迁徙雀类红头朱雀（Emberiza bruncieps）迁徙生理的影响。
在短日照（8L:16D）下饲养的感光朱雀被分为三组，分别接受 5、25 和 100 勒克斯的白天白光照度。此后，通过光周期操作，将三种生活史状态，即非迁徙（NM）、迁徙前（PM）和迁徙（MIG）状态引入朱雀。处于 MIG 状态的鸟类在经历了七个夜晚的迁徙躁动（夜间迁徙不安）后连续灌注，用于检测神经肽 Y（NPY）免疫组织化学，NPY 参与广泛的功能，包括鸟类的能量平衡、视觉和脂肪沉积。
我们发现光照度对运动活性和生理有不同的影响。受光照刺激的鸟类在 MIG 状态下表现出强烈的夜间活动。我们观察到鸟类在迁徙前出现过度摄食，100 勒克斯组的食物摄入量增加，这反映在 MIG 状态下的体重增加。圆状核周围 NPY 表达表明其在视觉敏锐度中的潜在作用，在 25 勒克斯光照下 NPY 细胞计数显著减少。
我们证明迁徙鸟类也可能受到白天光照变化的生理影响。我们观察到鸟类消耗食物的数量与光照度有关。这表明光照度也可能影响控制食物摄入的脑中枢。
