Although tissue fatty acid (FA) composition has been linked to whole-animal performance (e.g., aerobic endurance, metabolic rate, postexercise recovery) in a wide range of animal taxa, we do not adequately understand the pace of changes in FA composition and its implications for the ecology of animals. Therefore, we used a C4 to C3 diet shift experiment and compound-specific δ13C analysis to estimate the turnover rates of FAs in the polar and neutral fractions of flight muscle lipids (corresponding to membranes and lipid droplets) of exercised and sedentary zebra finches (Taeniopygia guttata). Turnover was fastest for linoleic acid (LA; 18:2n6) and palmitic acid (PA; 16:0), with 95% replacement times of 10.8-17.7 d in the polar fraction and 17.2-32.8 d in the neutral fraction, but was unexpectedly slow for the long-chain polyunsaturated FAs (LC-PUFAs) arachidonic acid (20:4n6) and docosahexaenoic acid (22:6n3) in the polar fraction, with 95% replacement in 64.9-136.5 d. Polar fraction LA and PA turnover was significantly faster in exercised birds (95% replacement in 8.5-13.3 d). Our results suggest that FA turnover in intramuscular lipid droplets is related to FA tissue concentrations and that turnover does not change in response to exercise. In contrast, we found that muscle membrane FA turnover is likely driven by a combination of selective LC-PUFA retention and consumption of shorter-chain FAs in energy metabolism. The unexpectedly fast turnover of membrane-associated FAs in muscle suggests that songbirds during migration could substantially remodel their membranes within a single migration stopover, and this may have substantial implications for how the FA composition of diet affects energy metabolism of birds during migration.

中文翻译：

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鸣禽的肌肉脂肪存储和膜中单个脂肪酸的动力学及其功能和生态意义。

尽管组织脂肪酸（FA）的组成与多种动物类群的整体动物性能（例如有氧耐力，代谢率，运动后恢复）有关，但我们仍不足以了解FA组成及其变化的步伐对动物生态的影响。因此，我们使用了从C4到C3的饮食转变实验和化合物特异性的δ13C分析来估计运动斑纹雀和久坐斑马雀（Taeniopygia）的飞行肌肉脂质（对应于膜和脂质滴）的极性和中性部分中FA的转换率guttata）。亚油酸（LA; 18：2n6）和棕榈酸（PA; 16：0）的周转速度最快，其中极性级分的10.8-17.7 d和中性级分的17.2-32.8 d的更换时间为95％，但对于极性级分中的长链多不饱和FAs（LC-PUFAs）花生四烯酸（20：4n6）和二十二碳六烯酸（22：6n3）出乎意料地缓慢，在64.9-136.5 d内有95％的取代。在运动鸟类中，极地分数LA和PA的周转速度显着加快（8.5-13.3 d中95％的替换率）。我们的结果表明，肌内脂质滴中的FA转换与FA组织浓度有关，并且转换不会响应运动而改变。相比之下，我们发现肌肉膜FA转换可能是由选择性LC-PUFA保留和能量代谢中短链FA的消耗共同驱动的。肌肉中与膜相关的FAs出乎意料的快速周转表明，在迁移过程中，鸣禽可能会在单个迁移中途停留时大幅重塑其膜，