Tapia-Monsalve Romina, Newsome Seth D, Sanchez-Hernandez Juan C, Bozinovic Francisco, Nespolo Roberto, Sabat Pablo
Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile.
Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA.
Oecologia. 2018 Sep;188(1):65-73. doi: 10.1007/s00442-018-4181-8. Epub 2018 Jun 8.
Life in saline environments represents a major physiological challenge for birds, particularly for passerines that lack nasal salt glands and hence are forced to live in environments that do not contain salty resources. Increased energy costs associated with increased salt intake, which in turn increases the production of reactive oxygen species, is likely a major selection pressure for why passerines are largely absent from brackish and marine environments. Here we measured basal metabolic rates (BMR) and oxidative status of free-ranging individuals of three species of Cinclodes, a group of passerine birds that inhabit marine and freshwater habitats in Chile. We used a combination of carbon, nitrogen, and hydrogen isotope data from metabolically active (blood) and inert (feathers) tissues to estimate seasonal changes in marine resource use and infer altitudinal migration. Contrary to our expectations, the consumption of marine resources did not result in higher BMR values and higher oxidative stress. Specifically, the marine specialist C. nigrofumosus had lower BMR than the other two species (C. fuscus and C. oustaleti), which seasonally switch between terrestrial and marine resources. C. fuscus had significantly higher total antioxidant capacity than the other two species (C. nigrofumosus and C. oustaleti) that consumed a relatively high proportion of marine resources. Nearly all studies examining the effects of salt consumption have focused on intraspecific acclimation via controlled experiments in the laboratory. The mixed results obtained from field- and lab-based studies reflect our poor understanding of the mechanistic link among hydric-salt balance, BMR, and oxidative stress in birds.
在盐碱环境中生存对鸟类来说是一项重大的生理挑战，尤其对于缺乏鼻盐腺、因而被迫生活在不含有咸资源环境中的雀形目鸟类而言。与盐分摄入增加相关的能量成本增加，进而增加了活性氧的产生，这可能是雀形目鸟类在半咸水和海洋环境中基本不存在的主要选择压力。在此，我们测量了三种Cinclodes属雀形目鸟类（栖息于智利海洋和淡水栖息地的一组鸟类）自由放养个体的基础代谢率（BMR）和氧化状态。我们结合了来自代谢活跃组织（血液）和惰性组织（羽毛）的碳、氮和氢同位素数据，以估计海洋资源利用的季节性变化并推断海拔迁移情况。与我们的预期相反，海洋资源的消耗并未导致更高的基础代谢率值和更高的氧化应激。具体而言，海洋特化物种黑烟鹡鸰的基础代谢率低于其他两个物种（棕鹡鸰和乌氏鹡鸰），后两者在陆地和海洋资源之间季节性切换。棕鹡鸰的总抗氧化能力显著高于其他两个消耗相对较高比例海洋资源的物种（黑烟鹡鸰和乌氏鹡鸰）。几乎所有研究盐消耗影响的研究都集中在通过实验室控制实验进行的种内适应上。从基于野外和实验室的研究中获得的混合结果反映出我们对鸟类水盐平衡、基础代谢率和氧化应激之间的机制联系了解不足。
