Department of Neurobiology, Physiology and Behavior, University of California Davis, One Shields Avenue, Davis, CA 95616, USA.
Department of Biology, University of Nevada Reno, 1664 North Virginia Street, Reno, NV 89557, USA.
Gen Comp Endocrinol. 2021 Jul 1;308:113784. doi: 10.1016/j.ygcen.2021.113784. Epub 2021 Apr 20.
Glucocorticoids, androgens, and prolactin regulate metabolism and reproduction, but they also play critical roles in immunomodulation. Since the introduction of avian malaria to Hawaii a century ago, low elevation populations of the Hawaii Amakihi (Chlorodrepanis virens) that have experienced strong selection by avian malaria have evolved increased resilience (the ability to recover from infection), while high elevation populations that have undergone weak selection remain less resilient. We investigated how variation in malaria selection has affected corticosterone, testosterone, and prolactin hormone levels in Amakihi during the breeding season. We predicted that baseline corticosterone and testosterone (which have immunosuppressive functions) would be reduced in low elevation and malaria-infected birds, while stress-induced corticosterone and prolactin (which have immunostimulatory functions) would be greater in low elevation and malaria-infected birds. As predicted, prolactin was significantly higher in malaria-infected than uninfected females (although more robust sample sizes would help to confirm this relationship), while testosterone trended higher in malaria-infected than uninfected males and, surprisingly, neither baseline nor stress-induced CORT varied with malaria infection. Contrary to our predictions, stress-induced corticosterone was significantly lower in low than high elevation birds while testosterone in males and prolactin in females did not vary by elevation, suggesting that Amakihi hormone modulation across elevation is determined by variables other than disease selection (e.g., timing of breeding, energetic challenges). Our results shed new light on relationships between introduced disease and hormone modulation, and they raise new questions that could be explored in experimental settings.
糖皮质激素、雄激素和催乳素调节代谢和生殖，但它们在免疫调节中也起着关键作用。自一个世纪前禽流感传入夏威夷以来，经历了禽流感强烈选择的低海拔夏威夷绿雀（Chlorodrepanis virens）已经进化出了更强的恢复力（从感染中恢复的能力），而经历了弱选择的高海拔种群仍然恢复力较弱。我们研究了疟疾选择的变化如何影响繁殖季节夏威夷绿雀的皮质酮、睾丸酮和催乳素激素水平。我们预测，低海拔和感染疟疾的鸟类的基础皮质酮和睾丸酮（具有免疫抑制功能）会降低，而低海拔和感染疟疾的鸟类的应激诱导皮质酮和催乳素（具有免疫刺激功能）会增加。正如预测的那样，感染疟疾的雌性催乳素明显高于未感染的雌性（尽管更大的样本量将有助于确认这种关系），而感染疟疾的雄性睾丸酮呈上升趋势，高于未感染的雄性，而且令人惊讶的是，无论是基础皮质酮还是应激诱导的皮质酮都与疟疾感染无关。与我们的预测相反，低海拔鸟类的应激诱导皮质酮明显低于高海拔鸟类，而雄性的睾丸酮和雌性的催乳素则不受海拔变化的影响，这表明，除了疾病选择（例如，繁殖时间、能量挑战）以外，其他因素决定了夏威夷绿雀在不同海拔高度的激素调节。我们的研究结果为引入疾病与激素调节之间的关系提供了新的认识，并提出了可以在实验环境中探讨的新问题。
