Colimitation of a freshwater herbivore by sterols and polyunsaturated fatty acids
Colimitation of a freshwater herbivore by sterols and polyunsaturated fatty acids
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DOI：
10.1098/rspb.2008.1540
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发表时间：
2009-05-22
影响因子：
4.7
通讯作者：
Wacker, Alexander
中科院分区：
文献类型：
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作者：
Martin-Creuzburg, Dominik;Sperfeld, Erik;Wacker, Alexander
为食草动物受到两种或多种必需营养素共同限制提供证据的经验数据很少，特别是在生化资源方面。这里提出了一个图形模型，它描述了草食动物在具有两种潜在限制资源的系统中的生长。为了验证这个模型，我们用食草动物大型溞进行了生活史实验，该大型水蚤以小聚蓝细菌为食，并在存在或不存在饱和量的二十碳五烯酸（EPA）的情况下补充越来越多的胆固醇。为了进行比较，D. magna 的饲料中含有不同比例的 S. elongatus 和富含胆固醇和 EPA 的真核藻类 Nannothropsis limnetica。在缺乏甾醇和 EPA 的饮食中，D. magna 的体细胞和种群生长最初受到甾醇缺乏的限制。随着甾醇可用性的增加，EPA 的共同限制变得明显，并且当满足甾醇需求时，生长限制因素从甾醇的限制转变为 EPA 的限制。这些数据意味着食草动物经常同时受到两种或多种必需营养素的限制。因此，必须将共限制的概念纳入评估草食动物营养限制生长动力学的模型中，以准确预测人口变化和人口动态。
Empirical data providing evidence for a colimitation of an herbivore by two or more essential nutrients are scarce, particularly in regard to biochemical resources. Here, a graphical model is presented, which describes the growth of an herbivore in a system with two potentially limiting resources. To verify this model, life-history experiments were conducted with the herbivore Daphnia magna feeding on the picocyanobacterium Synechococcus elongatus, which was supplemented with increasing amounts of cholesterol either in the presence or the absence of saturating amounts of eicosapentaenoic acid (EPA). For comparison, D. magna was raised on diets containing different proportions of S. elongatus and the cholesterol- and EPA-rich eukaryotic alga Nannochloropsis limnetica. Somatic and population growth of D. magna on a sterol- and EPA-deficient diet was initially constrained by the absence of sterols. With increased sterol availability, a colimitation by EPA became apparent and when the sterol requirements were met, the growth-limiting factor was shifted from a limitation by sterols to a limitation by EPA. These data imply that herbivores are frequently limited by two or more essential nutrients simultaneously. Hence, the concept of colimitation has to be incorporated into models assessing nutrient-limited growth kinetics of herbivores to accurately predict demographic changes and population dynamics.