Benefit of pulsation in soft corals
Benefit of pulsation in soft corals
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DOI：
10.1073/pnas.1301826110
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发表时间：
2013-05-28
影响因子：
11.1
通讯作者：
Genin, Amatzia
中科院分区：
文献类型：
--
作者：
Kremien, Maya;Shavit, Uri;Genin, Amatzia
Xeniidae 科的软珊瑚的触手表现出独特的、有节奏的脉动（电影 S1），拉马克在近 200 年前首次注意到这一点。然而，人们对这种永久的、耗费能量的运动的适应性益处知之甚少。使用原位水下粒子图像测速，我们发现脉动运动将水向上推并增强穿过珊瑚-水边界层的混合。引起的向上运动有效地防止了邻近珊瑚虫对水的再过滤，而混合的加强以及向上的流动大大增强了珊瑚的光合作用。对普通珊瑚 Heteroxenia fuscescens 进行的一系列受控实验室实验表明，脉动期间的净光合作用速率比珊瑚静止、非脉动状态期间高出一个数量级。当环境水中的氧气浓度被人为提高时，这种增强作用减弱，这表明光合作用的增强是由于珊瑚组织中氧气流出量增加所致。通过降低内部氧浓度，脉动缓解了高氧浓度条件下核酮糖-1,5-二磷酸羧化酶加氧酶 (RuBisCO) 对 CO2 的亲和力降低的问题。脉动的 H. fuscescens 的光合作用-呼吸比明显高于非脉动的软珊瑚和石珊瑚的光合作用-呼吸比。尽管脉动通常用于海洋移动动物的运动和过滤，但它在无柄（底部附着）物种中的出现仅限于古老的刺胞动物门的成员，在该门中，脉动用于加速水流和增强生理过程。
Soft corals of the family Xeniidae exhibit a unique, rhythmic pulsation of their tentacles (Movie S1), first noted by Lamarck nearly 200 y ago. However, the adaptive benefit of this perpetual, energetically costly motion is poorly understood. Using in situ underwater particle image velocimetry, we found that the pulsation motions thrust water upward and enhance mixing across the coral-water boundary layer. The induced upward motion effectively prevents refiltration of water by neighboring polyps, while the intensification of mixing, together with the upward flow, greatly enhances the coral's photosynthesis. A series of controlled laboratory experiments with the common xeniid coral Heteroxenia fuscescens showed that the net photosynthesis rate during pulsation was up to an order of magnitude higher than during the coral's resting, nonpulsating state. This enhancement diminished when the concentration of oxygen in the ambient water was artificially raised, indicating that the enhancement of photosynthesis was due to a greater efflux of oxygen from the coral tissues. By lowering the internal oxygen concentration, pulsation alleviates the problem of reduced affinity of ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) to CO2 under conditions of high oxygen concentrations. The photosynthesis-respiration ratio of the pulsating H. fuscescens was markedly higher than the ratios reported for nonpulsating soft and stony corals. Although pulsation is commonly used for locomotion and filtration in marine mobile animals, its occurrence in sessile (bottom-attached) species is limited to members of the ancient phylum Cnidaria, where it is used to accelerate water and enhance physiological processes.