Recovery rates for baleen whales that were decimated by exploitation vary between species and populations. Age determination is critical for the understanding of recovery trends and population structure, but determining age in free-ranging individuals remains challenging. Recent research has suggested that the methylation level of some genes in skin samples may provide age determinations with accuracy. We selected nine CpG sites from three genes (TET2, CDKN2A, and GRIA2) and analyzed them in 40 skin samples from known-age individuals pertaining to two different populations of fin whales from the North Atlantic. We observed significant correlations with age in five CpG sites. We used three of these CpG sites to perform an epigenetic age estimation. Predictions had a standard deviation of 2.94, but regression between observed and predicted ages showed a clear underestimation for older fin whales. For further development, we suggest: (1) screening for new CpG sites associated with age that exhibit higher variability between individuals, and (2) including older animals whenever the sampling allows it. We also observed subtle, but significant differences between the two populations studied in one of the CpG sites (TET2_CpG + 21). We attributed these differences to genetic differences or to the dissimilar environments that affect both populations.

中文翻译：

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北大西洋长须鲸中 TET2、GRIA2 和 CDKN2A 基因的 CpG 甲基化频率随年龄和种群之间的变化而变化

因开发而大量灭绝的须鲸的恢复率因物种和种群而异。年龄确定对于了解恢复趋势和种群结构至关重要，但确定自由放养个体的年龄仍然具有挑战性。最近的研究表明，皮肤样本中某些基因的甲基化水平可以提供准确的年龄测定。我们从三个基因（TET2、CDKN2A和GRIA2 ）中选择了九个 CpG 位点) 并对来自北大西洋两个不同长须鲸种群的已知年龄个体的 40 个皮肤样本进行了分析。我们在五个 CpG 位点观察到与年龄的显着相关性。我们使用其中三个 CpG 位点来进行表观遗传年龄估计。预测的标准偏差为 2.94，但观察到的和预测的年龄之间的回归表明，对年长的长须鲸的估计明显低估。为了进一步发展，我们建议：(1) 筛选与年龄相关的新 CpG 位点，这些位点在个体之间表现出更高的变异性，以及 (2) 只要​​采样允许，就包括老年动物。我们还观察到在 CpG 位点之一 (TET2_CpG + 21) 中研究的两个种群之间存在细微但显着的差异。