Raubenheimer D, Simpson S J
Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
J Exp Biol. 2003 May;206(Pt 10):1669-81. doi: 10.1242/jeb.00336.
We examined correlates of nutrient balancing with dietary range by comparing diet selection and ingestive, post-ingestive and performance-related responses to macronutrient imbalance in two species of grasshopper. One of the two species, Locusta migratoria (the African migratory locust), is a specialist grass-feeder, while the other, Schistocerca gregaria (the desert locust), is a generalist herbivore that includes both grasses and forbs in its diet. In ad libitum conditions, both species composed a balanced intake of the two macronutrients protein and carbohydrate from nutritionally complementary synthetic foods, but the composition of the selected diet differed, with the generalist selecting more protein, but not carbohydrate, than the grass-specialist. The grass-specialist, by contrast, retained ingested nitrogen more efficiently on the ad libitum diets. When confined to nutritionally imbalanced foods, both species regulated ingestion in such a way as to mitigate excesses as well as deficits of the two nutrients. The responses were, however, distinct in the two species, with the generalist feeder ingesting greater excesses of protein than the specialist. The species also differed in their post-ingestive responses to ingested excesses of nutrient, with the generalist but not the specialist using protein-derived carbon as an energy source when fed carbohydrate-deficient foods. The generalist also retained a higher level of body protein when confined to protein-deficient diets. The data suggested one functional reason why the generalist species selected a diet with higher protein content in the ad libitum treatment because, when confined to the nutritionally imbalanced foods, development rate peaked on higher protein foods for the generalist compared with the specialist. Many aspects of these data agree with the prediction that generalist-feeding animals should show greater behavioural and physiological flexibility in their responses to nutrient imbalance than do specialists.
我们通过比较两种蝗虫对常量营养素失衡的饮食选择以及摄食、摄食后和与性能相关的反应，研究了营养平衡与饮食范围的相关性。这两种蝗虫中的一种，即飞蝗（非洲迁徙蝗虫），是一种专门以草为食的动物，而另一种，即沙漠蝗，是一种多食性食草动物，其饮食中包括草和阔叶植物。在自由采食条件下，两种蝗虫都从营养互补的合成食物中摄入了蛋白质和碳水化合物这两种常量营养素的平衡摄入量，但所选饮食的组成有所不同，多食性蝗虫比专食草的蝗虫选择了更多的蛋白质，但碳水化合物的摄入量没有差异。相比之下，专食草的蝗虫在自由采食的饮食中能更有效地保留摄入的氮。当限制在营养不均衡的食物中时，两种蝗虫都通过调节摄食来减轻两种营养素的过量和不足。然而，两种蝗虫的反应有所不同，多食性食草动物摄入的蛋白质过量比专食性食草动物更多。两种蝗虫在对摄入的过量营养素的摄食后反应方面也存在差异，当喂食碳水化合物缺乏的食物时，多食性蝗虫但不是专食性蝗虫会将蛋白质衍生的碳用作能量来源。在限制于蛋白质缺乏的饮食时，多食性蝗虫也能保持较高水平的身体蛋白质。数据表明了多食性物种在自由采食处理中选择蛋白质含量较高的饮食的一个功能原因，因为当限制在营养不均衡的食物中时，与专食性蝗虫相比，多食性蝗虫在蛋白质含量较高的食物上发育速度达到峰值。这些数据的许多方面都与这样的预测一致，即多食性动物在对营养失衡的反应中应该比专食性动物表现出更大的行为和生理灵活性。
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