Determining the transfer and transformation of organic matter in food webs is a fundamental challenge that has implications for sustainable management of ecosystems. Fatty acids (FA) offer a potential approach for resolving complex diet mixtures of organisms because they provide a suite of molecular tracers. Yet, uncertainties in the degree of their biochemical modification by consumers, due to selective retention or metabolism, have limited their application. Here, we consolidated 316 controlled feeding studies of aquatic ectotherms (fishes and invertebrates) involving 1404 species–diet combinations to assess the degree of trophic modification of FA in muscle tissue. We found a high degree of variability within and among taxa in the %FA in consumer muscle tissue versus %FA in diet regression equations. Most saturated FA had weak relationships with the diet ( r 2 < 0.30) and shallow slopes ( m < 0.30), suggesting a lack of retention in muscle when fed in increasing amounts. Contrarily, several essential FA, including linoleic (18:2n-6) and α-linolenic acid (18:3n-3), exhibited significant relationships with the diet ( m > 0.35, r 2 > 0.50), suggesting supply limitations and selective retention in muscle by consumers. For all FA, relationships strengthened with increasing taxonomic specificity. We also demonstrated the utility of new correction equations by calculating the potential contributions of approximately 20 prey items to the diet of selected species of generalist fishes using a FA mixing model. Our analyses further reveal how a broad range of fishes and invertebrates convert or store these compounds in muscle tissue to meet physiological needs and point to their power in resolving complex diets in aquatic food webs. This article is part of the theme issue ‘The next horizons for lipids as ‘trophic biomarkers’: evidence and significance of consumer modification of dietary fatty acids’.

中文翻译：

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释放脂肪酸作为鱼类和水生无脊椎动物膳食示踪剂和代谢信号的力量

确定食物网中有机物的转移和转化是一项基本挑战，对生态系统的可持续管理具有影响。脂肪酸 (FA) 为解析生物体的复杂饮食混合物提供了一种潜在的方法，因为它们提供了一套分子示踪剂。然而，由于选择性保留或代谢，消费者对它们的生化修饰程度的不确定性限制了它们的应用。在这里，我们整合了 316 项水生变温动物（鱼类和无脊椎动物）的受控喂养研究，涉及 1404 个物种-饮食组合，以评估肌肉组织中 FA 的营养修饰程度。我们发现消费者肌肉组织中的 FA % 与饮食回归方程中的 %FA 相比，类群内部和类群之间存在高度变异性。大多数饱和 FA 与饮食的关系较弱（r 2< 0.30) 和浅坡 (米< 0.30），表明喂食量增加时肌肉缺乏保留。相反，几种必需的 FA，包括亚油酸 (18:2n-6) 和 α-亚麻酸 (18:3n-3)，与饮食表现出显着的关系（米> 0.35，r 2> 0.50），表明供应限制和消费者对肌肉的选择性保留。对于所有 FA，关系随着分类特异性的增加而加强。我们还通过使用 FA 混合模型计算大约 20 种猎物对选定的多面性鱼类的饮食的潜在贡献，证明了新校正方程的实用性。我们的分析进一步揭示了多种鱼类和无脊椎动物如何在肌肉组织中转化或储存这些化合物以满足生理需求，并指出它们在解决水生食物网中复杂饮食方面的能力。本文是主题“脂质作为‘营养生物标志物’的下一个前景：消费者改变膳食脂肪酸的证据和意义”的一部分。