Allocation of essential lipids in Daphnia magna during exposure to poor food quality
Allocation of essential lipids in Daphnia magna during exposure to poor food quality
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DOI：
10.1111/j.1365-2435.2007.01274.x
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发表时间：
2007-08
影响因子：
5.2
通讯作者：
A. Wacker;D. Martin‐Creuzburg
中科院分区：
文献类型：
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作者：
A. Wacker;D. Martin‐Creuzburg
1. 在自然界中，食物状况是暂时变化的，迫使消费者在资源分配过程中进行权衡。特别是，在恶劣的食物条件下，例如在蓝藻繁殖期间，食草动物必须优化它们的资源分配以最大限度地提高适应性，并面临两个决定：(i)个体可能试图将获得的基本资源分配给生殖组织或用于自身维持；（ii）个体可能决定优化其卵的化学质量。2. 由于蓝藻细菌缺乏一些必需的脂质，导致水蚤（一种重要的淡水草食动物）的生长和繁殖力下降，我们研究了实验无毒蓝藻华期间大水蚤的施特劳斯脂质分配，如多不饱和脂肪酸（PUFAs）和胆固醇。3. 一般来说，我们发现母体将特别重要的omega-3 (n-3) PUFAs，特别是二十碳五烯酸（EPA）大量投入到卵子中。EPA在卵中的浓度是体细胞组织的2.4倍，这是一种累积效应，在蓝藻食物条件下没有显著变化。4. 在较差的条件下，D. magna不仅减少了卵的产量，而且原则上也将卵和体细胞组织中先前高浓度的EPA降低了相似的程度。与EPA相比，α-亚麻酸和胆固醇的浓度虽然低于EPA，但在卵中比在体细胞组织中更稳定，在体细胞组织中浓度降低。5. 当食物质量提高时，马格纳大蠊能够完全恢复其体细胞组织和卵中的脂肪酸浓度。6. 本研究表明，其食物中特定脂质的含量明显影响大鼠的资源分配，并表明胆固醇对体细胞生长很重要，而PUFAs主要用于繁殖。由于必需脂质在卵子中的投入减少意味着动物后代在不良食物条件下的适应性降低，这可能对种群动态产生强烈影响，这可能对其他物种也有效。
1. In nature, food conditions change temporally and force consumers into trade-offs during resource allocation. In particular, under poor food conditions, for example during cyanobacterial blooms, herbivores have to optimize their resource allocation to maximize fitness, and face two decisions: (i) an individual might attempt to allocate acquired essential resources to reproductive tissues or use them for its own maintenance; and (ii) an individual might decide to optimize the chemical quality of its eggs. 2. As cyanobacteria feature a deficiency in some essential lipids that leads to a decline in the growth and fecundity of Daphnia, an important freshwater herbivore, we investigated Daphnia magna's Strauss allocation of lipids such as polyunsaturated fatty acids (PUFAs) and cholesterol during an experimental non-toxic cyanobacterial bloom. 3. Generally, we found a substantial maternal investment of the particularly important omega-3 (n-3) PUFAs, in particular eicosapentaenoic acid (EPA), into the eggs. The concentration of EPA was 2·4-fold higher in eggs than in somatic tissue, a cumulative effect, which was not significantly changed under cyanobacterial food conditions. 4. Under poor conditions, D. magna not only decreased the number of eggs produced but, in principle, reduced the previously high concentrations of EPA in both eggs and somatic tissues to a similar degree. In contrast to EPA, the concentrations of α-linolenic acid and cholesterol, although lower than EPA, were more homeostatic in eggs than in somatic tissues, in which concentrations decreased. 5. When food quality was improved, D. magna were able to recover completely the fatty acid concentrations in their somatic tissues and eggs. 6. This study shows that the content of particular lipids in its food clearly affects resource allocation in D. magna, and suggests that cholesterol is important for somatic growth, while PUFAs are primarily needed for reproduction. As a decreasing investment of essential lipids into eggs implies a reduced fitness of the animals' progeny under poor food conditions, this could have a strong impact on population dynamics, which might also be valid for other species.