Stress in paradise: effects of elevated corticosterone on immunity and avian malaria resilience in a Hawaiian passerine

Vertebrates confronted with challenging environments often experience an increase in circulating glucocorticoids, which result in morphological, physiological, and behavioral changes that promote survival. However, chronically elevated glucocorticoids can suppress immunity, which may increase susceptibility to disease. Since the introduction of avian malaria to Hawaii a century ago, low elevation populations of Hawaii Amakihi (Chlorodrepanis virens) have undergone strong selection by avian malaria and evolved increased resilience (the ability to recover from infection), while populations at high elevation with few vectors have not undergone selection and remain susceptible. We investigated how experimentally elevated corticosterone affects the ability of high and low elevation male Amakihi to cope with avian malaria by measuring innate immunity, hematocrit, and malaria parasitemia. Corticosterone implants resulted in a decrease in hematocrit in high and low elevation birds but no change...当脊椎动物面临挑战性环境时，其循环糖皮质激素（glucocorticoids）水平通常会升高，进而触发形态、生理及行为层面的适应性改变，以提升生存几率。然而，长期升高的糖皮质激素会抑制机体免疫功能，进而增加个体对疾病的易感性。自一个世纪前禽疟疾（avian malaria）传入夏威夷后，低海拔种群的夏威夷旋蜜雀（Chlorodrepanis virens）已受到禽疟疾的强烈定向选择，并演化出更高的抗性（即从感染中恢复的能力）；而病媒昆虫稀少的高海拔种群未经历此类选择，仍对疾病保持易感状态。本研究通过检测先天免疫功能、血细胞比容（hematocrit）及疟疾原虫血症（malaria parasitemia）水平，探究实验性升高的皮质酮（corticosterone）对高、低海拔雄性夏威夷旋蜜雀应对禽疟疾能力的影响。皮质酮植入处理使高、低海拔个体的血细胞比容均出现下降，但未观察到其他变化……