Effects of temperature and dietary sterol availability on growth and cholesterol allocation of the aquatic keystone species Daphnia
Effects of temperature and dietary sterol availability on growth and cholesterol allocation of the aquatic keystone species Daphnia
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DOI：
10.1242/jeb.031401
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发表时间：
2009-10-01
影响因子：
2.8
通讯作者：
Wacker, Alexander
中科院分区：
文献类型：
--
作者：
Sperfeld, Erik;Wacker, Alexander
水温升高会促进蓝藻水华的发生，这可能对水生食草动物有害。特别是，通常占主导地位的甲壳类动物可能会受到负面影响，因为蓝细菌缺乏植物甾醇，甲壳类动物需要植物甾醇来形成膜成分胆固醇，而胆固醇反过来在热适应中发挥作用。在这里，我们确定了温度对沿着膳食胆固醇梯度饲养的关键物种大型溞的生长、繁殖以及膳食甾醇在体组织和卵中的分配的影响。随着膳食胆固醇可用性的增加，D. magna 的质量特异性生长率增加至初始限制水平，该水平随着温度的升高而增加。这表明在较高温度下生长对胆固醇的需求较高，并且可能解释了在最高温度下繁殖的雌性的窝数始终较小的原因。个体的胆固醇含量随着膳食胆固醇的增加而增加；这种增加在较高温度下增强，表明组织（特别是膜）对胆固醇的需求更高。令人惊讶的是，水蚤在温度和膳食甾醇可用性方面表现出不同的分配策略。鸡蛋的胆固醇含量在较高温度下增加，这表明雌性将更多的胆固醇分配给后代，大概是为了确保卵子充分发育。然而，当膳食胆固醇受到限制时，雌性不会将更多的胆固醇分配给卵子。我们的数据表明，在蓝藻水华期间，水蚤潜在的饮食甾醇限制在较高的水温下可能会加剧，这可能会随着全球变暖而发生。
Enhanced water temperatures promote the occurrence of cyanobacterial blooms, which may be detrimental to aquatic herbivores. Especially, the often-dominant crustaceans could be negatively affected because cyanobacteria are deficient in phytosterols, which are required by the crustaceans to form the membrane component cholesterol, which in turn plays a role in thermal adaptation. Here, we determined the influence of temperature on growth, reproduction and the allocation of dietary sterol into somatic tissues and eggs of the keystone species Daphnia magna raised along a dietary cholesterol gradient. Mass-specific growth rates of D. magna increased with the increasing availability of dietary cholesterol up to an incipient limiting level, which increased with increasing temperature. This indicates a higher demand for cholesterol for growth at higher temperatures and may explain the consistently smaller clutch sizes of reproducing females at the highest temperature. The cholesterol content of the individuals increased with increasing dietary cholesterol; this increase was enhanced at higher temperatures, indicating a higher demand for cholesterol for tissues and probably specifically for membranes. Surprisingly, the daphnids showed different allocation strategies with regard to temperature and dietary sterol availability. The cholesterol content of eggs was enhanced at higher temperature, which suggested that females allocate more cholesterol to their offspring, presumably to ensure sufficient egg development. When dietary cholesterol was limiting, however, females did not allocate more cholesterol to their eggs. Our data suggest that during cyanobacterial blooms, a potential dietary sterol limitation of Daphnia can be intensified at higher water temperatures, which can occur with global warming.