Tiwari Jyoti, Sur Sayantan, Naseem Asma, Gupta Preeti, Fatima Shirin, Rani Sangeeta, Malik Shalie
Department of Zoology, University of Lucknow, Lucknow, Uttar Pradesh 226007, India.
Department of Zoology, University of Lucknow, Lucknow, Uttar Pradesh 226007, India; School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Glasgow, United Kingdom.
J Photochem Photobiol B. 2025 Jan;262:113081. doi: 10.1016/j.jphotobiol.2024.113081. Epub 2024 Dec 10.
Animals use photic cues to time their daily and seasonal activity. The role of photoperiod has been much investigated in seasonal responses, but the role of light intensity is less understood in passerine finches. We investigated if and how daytime light intensity influences photoinduced migratory phenologies and hypothalamic mRNA expressions in a Palearctic-Indian migratory finch, redheaded bunting (Emberiza bruniceps). Photoperiodic manipulations were employed to induce winter-nonmigratory (NM), premigratory (PM), and migratory (MIG) states in photosensitive buntings. In each life history state, the birds were further subjected to 0.055 (low), 0.277 (medium), or 1.11 W/m (high) (N = 5 each) light intensity treatment. The low daytime light intensity dampened the locomotor activity rhythm and delayed the onset of Zugunruhe. We found life history-dependant but not light intensity-dependant changes in body mass, fat score, and testis volume. Plasma corticosterone levels were increased under the low-light intensity group in the migratory state. The buntings were foraging throughout the night in the migratory state, aiding body fattening. Front and back sleep were drastically reduced during the migratory phase under all three light intensities. In the migratory state, we found elevated hypothalamic IL1B and IL6 expression in medium and high-light intensity groups, which had significantly reduced sleep duration. In the winter nonmigratory state, the expression of CAMK2 correlated with daytime activity and active wakefulness of buntings. The decreased GHRH expression correlates with the reduction in total sleep in migrating buntings. Overall, daytime light intensity emerges as a key factor that fine-tunes the photoperiodic response and regulates active and sleep behaviour in migratory buntings.
动物利用光信号来安排它们的日常和季节性活动。光周期在季节性反应中的作用已得到大量研究，但光照强度在雀形目鸣禽中的作用却鲜为人知。我们研究了白天光照强度是否以及如何影响古北界-印度迁徙雀类红头鹀（Emberiza bruniceps）的光诱导迁徙物候和下丘脑mRNA表达。采用光周期处理来诱导光敏性鹀进入冬季非迁徙（NM）、迁徙前（PM）和迁徙（MIG）状态。在每种生活史状态下，鸟类进一步接受0.055（低）、0.277（中）或1.11 W/m（高）（每组N = 5）的光照强度处理。低白天光照强度减弱了运动活动节律并延迟了迁徙不安的开始。我们发现体重、脂肪评分和睾丸体积的变化取决于生活史而非光照强度。在迁徙状态下，低光照强度组的血浆皮质酮水平升高。迁徙状态下的鹀类整夜觅食，有助于积累身体脂肪。在所有三种光照强度下，迁徙阶段的前睡眠和后睡眠都大幅减少。在迁徙状态下，我们发现中、高光照强度组的下丘脑IL1B和IL6表达升高，睡眠持续时间显著缩短。在冬季非迁徙状态下，CAMK2的表达与鹀类的白天活动和主动觉醒相关。GHRH表达的降低与迁徙鹀类总睡眠的减少相关。总体而言，白天光照强度成为微调光周期反应并调节迁徙鹀类活动和睡眠行为的关键因素。
