Institute of Biomedicine/Anatomy, School of Medicine, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland.
Department of Environmental and Biological Sciences, Faculty of Science and Forestry, University of Eastern Finland, Joensuu, Finland.
PLoS One. 2018 Sep 17;13(9):e0204207. doi: 10.1371/journal.pone.0204207. eCollection 2018.
Fatty acid (FA) signatures (FAS) are important tools to assess the foraging ecology of wild animals. The present study was conducted to assess how well the general FAS and the proportions of individual FA are preserved in fat samples stored at different temperatures (-196, -80, -20, +4 and +20°C). Using three species (laboratory rat, American mink and rainbow trout), FAS were determined immediately upon sampling. Thereafter, eight subsamples per storage temperature from the inner part of the sample unaffected by oxygen and light were re-analyzed after 1, 2, 3, 7, 28, 84 and 168 days. Each time the remaining sample was sealed in its vial after replacing air with nitrogen gas. The results were tested with the mixed model and discriminant analyses. Generally, the FAS were well preserved regardless of storage temperature, and only a few major FA showed significant changes even after the 6-month period at room temperature. After an initial first-day change in proportions, presumably due to post-mortem enzymatic activities, the remaining minor changes could not be clearly attributed to either further autolysis, decomposition or autoxidation. In the discriminant analysis, the species-specific differences dominated and remained distinct even after 6 months. Furthermore, the analysis mostly classified the samples preserved at sub- and above-freezing temperatures separate from each other, and the general deviation from the initial analysis results was present as early as after 1 day. If FAS are to be analyzed in a very precise manner, the analysis should be performed immediately upon sampling. However, FAS remain adequately reliable for long periods of time even without preservation in deep freeze, widening the availability of potential samples for studies on foraging ecology and related disciplines.
脂肪酸（FA）特征（FAS）是评估野生动物觅食生态的重要工具。本研究旨在评估一般 FAS 和单个 FA 比例在不同温度（-196、-80、-20、+4 和+20°C）下储存的脂肪样本中保存得如何。使用三种物种（实验室大鼠、美洲水貂和虹鳟鱼），在采样后立即确定 FAS。此后，从不受氧气和光照影响的样本内部，每个储存温度取 8 个样本，在 1、2、3、7、28、84 和 168 天后重新分析。每次在用氮气替换空气后，将剩余的样本密封在小瓶中。结果用混合模型和判别分析进行测试。一般来说，FAS 无论储存温度如何都保存得很好，即使在室温下放置 6 个月后，也只有少数主要 FA 发生显著变化。在最初的第一天比例变化后，可能是由于死后酶活性，其余的小变化不能明确归因于进一步的自溶、分解或自动氧化。在判别分析中，种间差异占主导地位，即使在 6 个月后仍然明显。此外，分析主要将保存在亚冷冻和以上温度下的样本彼此分开，并且从第一天开始就存在与初始分析结果的一般偏差。如果要非常精确地分析 FAS，则应在采样后立即进行分析。然而，即使没有在深冻中保存，FAS 也可以长时间保持足够的可靠性，从而为觅食生态和相关学科的研究提供更多潜在样本。
