Department of Zoology, Mizoram University, Aizawl, Mizoram, 976004, India.
Department of Zoology, Mizoram University, Aizawl, Mizoram, 976004, India.
Gen Comp Endocrinol. 2021 Jan 15;301:113654. doi: 10.1016/j.ygcen.2020.113654. Epub 2020 Oct 29.
The majority of birds use environmental cues to time their reproduction. Photoperiod is the most dominant cue, but other environmental factors may play a critical role in successful reproduction. Some previous studies show the effect of temperature on the timing of nest building and reproduction. Here we tested if the temperature can modulate the reproductive responses of tree sparrows. Three experiments were performed on adult male birds. In experiment 1, birds (n = 5/group) were exposed to either high (30 ± 2 °C) or low temperature (20 ± 2 °C). Change in body mass, bill color, and testes volume was recorded every 30 days. In experiment 2, a similar temperature protocol was followed, but birds were euthanized after 30 days. In experiment 3, birds were first exposed to SD (8L:16D) for 30 days but either with high (30 ± 2 °C) or low temperature (20 ± 2 °C). After 30 days, birds were exposed to LD (14L:10D), but half of the high-temperature birds were moved to low temperature, and half of the low-temperature birds were moved to high temperature. After 30 days, all birds were euthanized. In experiment 2 and 3 immediately after euthanization birds, blood samples were collected, serum was used for hormone assay. mRNA levels of thyroid-stimulating hormone-β (Tshβ), type 2 deiodinase (Dio2), type 3 deiodinase (Dio3), gonadotropin-releasing hormone (GnRH) and gonadotropin inhibitory hormone (GnIH) were measured in hypothalamic tissue. Results from experiment 1 show that high temperature attenuates the testicular responses and accelerates the timing of regression. Experiment 2 shows that on day 30, testicular responses are similar, but reproductive genes express differentially in two groups. Experiment 3 shows that exposure to high temperatures during the photosensitive stage affects the testicular response at the poststimulatory state. Together, these findings suggest that high temperature modulates reproductive responses of tree sparrow.
大多数鸟类利用环境线索来调节繁殖时间。光周期是最主要的线索，但其他环境因素在成功繁殖中可能起着关键作用。一些先前的研究表明，温度对筑巢和繁殖时间有影响。在这里，我们测试了温度是否可以调节树麻雀的繁殖反应。对成年雄性鸟类进行了三项实验。在实验 1 中，将 5 只鸟/组分别暴露于高温（30±2°C）或低温（20±2°C）下。每 30 天记录一次体重、喙色和睾丸体积的变化。在实验 2 中，遵循类似的温度方案，但在 30 天后处死鸟类。在实验 3 中，鸟类首先暴露于 SD（8L:16D）30 天，但温度分别为高温（30±2°C）或低温（20±2°C）。30 天后，鸟类暴露于 LD（14L:10D），但一半的高温鸟类转移到低温，一半的低温鸟类转移到高温。30 天后，所有鸟类均被安乐死。在实验 2 和 3 中，鸟类在安乐死后立即采集血液样本，血清用于激素测定。在下丘脑组织中测量了促甲状腺激素-β（Tshβ）、2 型脱碘酶（Dio2）、3 型脱碘酶（Dio3）、促性腺激素释放激素（GnRH）和促性腺激素抑制激素（GnIH）的 mRNA 水平。实验 1 的结果表明，高温会减弱睾丸反应并加速退化的时间。实验 2 表明，在第 30 天，睾丸反应相似，但两组的生殖基因表达不同。实验 3 表明，在光敏感阶段暴露于高温会影响刺激后状态下的睾丸反应。总之，这些发现表明高温调节了树麻雀的繁殖反应。
