Nematodes as important source for omega-3 long-chain fatty acids in the soil food web and the impact in nutrition for higher trophic levels

几种土壤无脊椎动物，特别是线虫，但也弹尾目和捕食螨，被指定为ω-3家族的长链多不饱和脂肪酸（ω3 LC-PUFA）的来源。这些化合物在动物中具有重要的生理意义，通常被认为在陆地食物网中不广泛存在。我们的研究表明，富含ω3 LC-PUFA的线虫饲料对弹尾目和螨类的适合度有显著的促进作用，从而增加了生物量和繁殖。这表明，ω3 LC PUFA的生物合成是昂贵的，尽管具有从头合成的能力，但通过食物摄取对消费者是有利可图的。有趣的是，在同一生境中，能够从头合成ω3 LC-PUFA的类群与不能从头合成的密切相关类群之间存在共存关系。新项目现在提出问题--这种从头合成的生理和生态优势是什么？它还旨在缩小所需酶机制的知识差距。为了实现这些目标，我们将结合联合收割机生物化学（脂肪酸去饱和酶的酶活性）和生理学（应激抗性、竞争强度和学习行为）方法，以更深入地了解ω3 LC-PUFA不依赖食物供应的重要性。结果将通过实地调查的经验数据来完成，该实地调查比较了从头合成ω3 LC-PUFA的遗传先决条件与在不同土壤生境中收集的相应线虫物种的生活策略。因此，拟议的项目将证明ω3 LC-PUFA作为土壤食物网相互作用的重要驱动力的作用。

Several soil invertebrates, especially nematodes but also collembola and predatory mites, were assigned as a source of long-chain polyunsaturated fatty acids of the omega-3 family (ω3 LC-PUFAs). These are well recognized compounds of great physiological importance in animals, and commonly are regarded as not widely available in terrestrial food webs. Our studies showed that the fitness of Collembola and mites significantly benefited from ω3 LC-PUFA rich nematode diet, resulting in increased biomass and reproduction. This suggest that the biosynthesis of ω3 LC PUFA is costly and uptake by food is profitable for consumers, despite capability for de novo synthesis. Interestingly, co-existence in the same habitat occurs between taxa that can de novo synthesize ω3 LC-PUFAs with closely related taxa that cannot.The new project now asks - what are the physiological and ecological advantages of this de novo synthesis? It further aims to close knowledge gaps in the required enzymatic mechanisms. To achieve these goals, we will combine biochemical (enzymatic activity of fatty acid desaturases) and physiological (stress resistance, competition strength and learning behavior) approaches to gain deeper understanding in the importance of a food independent supply with ω3 LC-PUFA. The results will be completed by empirical data from a field survey comparing the genetic prerequisites to de novo synthesize ω3 LC-PUFA with life strategy of the corresponding nematode species collected in different soil habitats. Thereby, the proposed project will prove the role of ω3 LC-PUFA as an important driving force for interactions in the soil food web.