Metabolic stoichiometry and the fate of excess carbon and nutrients in consumers
Metabolic stoichiometry and the fate of excess carbon and nutrients in consumers
复制标题
DOI：
10.1086/426598
复制
发表时间：
2005-01-01
影响因子：
2.9
通讯作者：
Urabe, J
中科院分区：
文献类型：
--
作者：
Anderson, TR;Hessen, DO;Urabe, J
动物遇到营养不平衡的食物时，应释放超出需要量的元素，以维持整体动态平衡。然而，量化这些过度行为并预测它们的命运是有问题的。建立了一个新的消费者化学计量学模型，该模型在代谢预算中纳入了单独的条款，即摄取底物的同化及其相关成本、蛋白质周转、其他基础成本，如渗透调节，以及使用剩余底物进行生产。该模型表明，过量的C和非限制性营养物质的释放通常在食用陆地和水生系统中常见的营养缺乏的牧草的动物的总新陈代谢预算中占有很大比例。维护成本不仅是C，而且是N和P，因此即使在摄入量较低的情况下，食物质量也很重要。许多多面手消费者在他们的饮食中经历了短期和不可预测的波动。模型输出与其中一个消费者--水蚤的数据比较表明，肠道吸收后操作的机制很可能是调节这些生物体中过量的C、N和P的主要手段，特别是与生化或机械工作以及碳和营养物质的排泄脱钩的呼吸作用。这种化学计量学调节的释放通常是有机的，而不是无机的，对生态系统中自养和异养过程的平衡产生重要影响。
Animals encountering nutritionally imbalanced foods should release elements in excess of requirements in order to maintain overall homeostasis. Quantifying these excesses and predicting their fate is, however, problematic. A new model of the stoichiometry of consumers is formulated that incorporates the separate terms in the metabolic budget, namely, assimilation of ingested substrates and associated costs, protein turnover, other basal costs, such as osmoregulation, and the use of remaining substrates for production. The model indicates that release of excess C and nonlimiting nutrients may often be a significant fraction of the total metabolic budget of animals consuming the nutrient-deficient forages that are common in terrestrial and aquatic systems. The cost of maintenance, in terms of not just C but also N and P, is considerable, such that food quality is important even when intake is low. Many generalist consumers experience short-term and unpredictable fluctuations in their diets. Comparison of model output with data for one such consumer, Daphnia, indicates that mechanisms operating postabsorption in the gut are likely the primary means of regulating excess C, N, and P in these organisms, notably respiration decoupled from biochemical or mechanical work and excretion of carbon and nutrients. This stoichiometrically regulated release may often be in organic rather than inorganic form, with important consequences for the balance of autotrophic and heterotrophic processes in ecosystems.