Limnological Institute, University of Konstanz, Mainaustrasse 252, 78464, Constance, Germany.
BMC Ecol. 2018 Dec 14;18(1):57. doi: 10.1186/s12898-018-0213-9.
The relative importance of nutrients derived from different sources for tissue synthesis is crucial for predicting a species responds to changes in food availability. The ecological and physiological strategies that govern the incorporation and routing of nutrients for reproduction are often well understood. However, the role and adaptive value of both species and individual variation during early life-stage remain elusive. In freshwater systems, dietary nutrient allocation to somatic tissue should be favoured when dietary source peaks and resource limitation may hinder flexible resource allocation. We used carbon and nitrogen stable isotopes (δC and δN) to examine metabolic nutrient routing and resource allocation from four dietary sources used to biosynthesize three somatic tissues of emerging subimago Ephemera danica. Aquatic emerging insects, such as the mayfly E. danica, are well suited for such studies. This is because, while burrowing nymph phase is a detritivores feeders with several early life-stages of metamorphosis, adult insects do not feed during this period but do utilize energy.
Constructed models to predict percent proportional contribution of source to tissue showed that terrestrial detritus was the dominant nutrient source for abdomen, head and wing with mean values of 57%, 65% and 73%, respectively. There was evidence for differential resource allocation, as insect partitioned periphyton and sediment (but also seston) elements for tissue synthesis. Utilizing individual-specimen based relationship in isotope value; we derived tissue specific isotopic niche estimates, for the different tissue-source combinations.
Results indicate that tissue selection is crucial for isotopic ecological measurements in arthropods. Mayfly has long been used as bio-indicator of freshwater ecosystems and their larvae show rapid response to environmental changes. In light of the recent evidence of drastic reduction in flying insect mass in Germany, developing a system using isotopic tools to trace nutrient flow in this important taxon will assist conservation and management efforts.
不同来源的营养物质对组织合成的相对重要性对于预测物种对食物供应变化的反应至关重要。通常，控制营养物质用于繁殖的吸收和分配的生态和生理策略是众所周知的。然而，在生命早期阶段，物种和个体变异的作用和适应价值仍然难以捉摸。在淡水系统中，当饮食源达到峰值且资源限制可能阻碍灵活的资源分配时，应该优先考虑将膳食营养物质分配给体细胞组织。我们使用碳和氮稳定同位素（δC 和 δN）来研究新兴 subimago Ephemera danica 的四种饮食源用于合成三种体细胞组织的代谢营养物质吸收和资源分配。水生新兴昆虫，如蜉蝣 E. danica，非常适合此类研究。这是因为，虽然在掘洞的若虫阶段是食碎屑者，有几个早期的变态阶段，但在这个阶段，成虫不进食，但会利用能量。
构建的模型来预测源对组织的比例贡献表明，陆地碎屑是腹部、头部和翅膀的主要营养源，平均值分别为 57%、65%和 73%。有证据表明存在资源分配的差异，因为昆虫将附生藻类和沉积物（但也包括悬浮物）元素分配用于组织合成。利用个体标本的同位素值关系；我们得出了不同组织-源组合的组织特异性同位素生态位估计值。
结果表明，组织选择对于节肢动物的同位素生态测量至关重要。蜉蝣长期以来一直被用作淡水生态系统的生物指标，其幼虫对环境变化表现出快速反应。鉴于最近在德国发现飞行昆虫数量急剧减少的证据，开发一种使用同位素工具追踪这个重要类群的营养物质流动的系统将有助于保护和管理工作。
