Twining Cornelia W, Brenna J Thomas, Lawrence Peter, Shipley J Ryan, Tollefson Troy N, Winkler David W
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853;
Division of Nutrition, Cornell University, Ithaca, NY 14853;
Proc Natl Acad Sci U S A. 2016 Sep 27;113(39):10920-5. doi: 10.1073/pnas.1603998113. Epub 2016 Sep 16.
Once-abundant aerial insectivores, such as the Tree Swallow (Tachycineta bicolor), have declined steadily in the past several decades, making it imperative to understand all aspects of their ecology. Aerial insectivores forage on a mixture of aquatic and terrestrial insects that differ in fatty acid composition, specifically long-chain omega-3 polyunsaturated fatty acid (LCPUFA) content. Aquatic insects contain high levels of both LCPUFA and their precursor omega-3 PUFA, alpha-linolenic acid (ALA), whereas terrestrial insects contain much lower levels of both. We manipulated both the quantity and quality of food for Tree Swallow chicks in a full factorial design. Diets were either high-LCPUFA or low in LCPUFA but high in ALA, allowing us to separate the effects of direct LCPUFA in diet from the ability of Tree Swallows to convert their precursor, ALA, into LCPUFA. We found that fatty acid composition was more important for Tree Swallow chick performance than food quantity. On high-LCPUFA diets, chicks grew faster, were in better condition, and had greater immunocompetence and lower basal metabolic rates compared with chicks on both low LCPUFA diets. Increasing the quantity of high-LCPUFA diets resulted in improvements to all metrics of performance while increasing the quantity of low-LCPUFA diets only resulted in greater immunocompetence and lower metabolic rates. Chicks preferentially retained LCPUFA in brain and muscle when both food quantity and LCPUFA were limited. Our work suggests that fatty acid composition is an important dimension of aerial insectivore nutritional ecology and reinforces the importance of high-quality aquatic habitat for these declining birds.
曾经数量丰富的食虫鸟类，如树燕（Tachycineta bicolor），在过去几十年中数量持续下降，因此有必要全面了解它们的生态习性。食虫鸟类以水生昆虫和陆生昆虫为食，这两类昆虫的脂肪酸组成有所不同，特别是长链ω-3多不饱和脂肪酸（LCPUFA）的含量。水生昆虫含有高水平的LCPUFA及其前体ω-3多不饱和脂肪酸α-亚麻酸（ALA），而陆生昆虫的这两种物质含量则低得多。我们采用全因子设计，对树燕雏鸟的食物数量和质量进行了控制。食物要么富含LCPUFA，要么LCPUFA含量低但ALA含量高，这样我们就能区分日粮中直接的LCPUFA的影响与树燕将其前体ALA转化为LCPUFA的能力。我们发现，脂肪酸组成对树燕雏鸟的生长表现比食物数量更为重要。与两种低LCPUFA日粮喂养的雏鸟相比，高LCPUFA日粮喂养的雏鸟生长更快、身体状况更好、免疫能力更强且基础代谢率更低。增加高LCPUFA日粮的数量会使各项生长指标都得到改善，而增加低LCPUFA日粮的数量只会提高免疫能力并降低代谢率。当食物数量和LCPUFA都有限时，雏鸟会优先将LCPUFA保留在大脑和肌肉中。我们的研究表明，脂肪酸组成是食虫鸟类营养生态学的一个重要方面，并强化了优质水生栖息地对这些数量减少的鸟类的重要性。
