Pondaven Philippe, Gallinari Morgane, Chollet Sophie, Bucciarelli Eva, Sarthou Géraldine, Schultes Sabine, Jean Frédéric
Laboratoire des Sciences de l'Environnement Marin, LEMAR, UMR UBO-CNRS 6539, Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, Place Nicolas Copernic, 29280 Plouzané, France.
Protist. 2007 Jan;158(1):21-8. doi: 10.1016/j.protis.2006.09.002. Epub 2006 Nov 1.
In aquatic environments, diatoms (Bacillariophyceae) constitute a central group of microalgae which contribute to about 40% of the oceanic primary production. Diatoms have an absolute requirement for silicon to build-up their silicified cell wall in the form of two shells (the frustule). To date, changes in diatom cell wall silicification have been only studied in response to changes in the growth environment, with consistent increase in diatom silica content when specific growth rates decrease under nutrient or light limitations. Here, we report the first evidence for grazing-induced changes in cell wall silicification in a marine diatom. Cells grown in preconditioned media that had contained both diatoms and herbivores are significantly more silicified than diatoms grown in media that have contained diatoms alone or starved herbivores. These observations suggest that grazing-induced increase in cell wall silicification can be viewed as an adaptive reaction in habitats with variable grazing pressure, and demonstrate that silicification in diatoms is not only a constitutive mechanical protection for the cell, but also a phenotypically plastic trait modulated by grazing. In turn, our results corroborate the idea that plant-herbivore interactions, beyond grazing sensu stricto, contribute to drive ecosystem structure and biogeochemical cycles in the ocean.
在水生环境中，硅藻（硅藻纲）是微藻的核心类群，约占海洋初级生产力的40%。硅藻绝对需要硅来构建其硅化细胞壁，细胞壁由两个壳（壳套）组成。迄今为止，硅藻细胞壁硅化作用的变化仅在其对生长环境变化的响应中得到研究，当在营养或光照限制下特定生长速率降低时，硅藻的硅含量会持续增加。在此，我们首次报道了海洋硅藻中摄食诱导的细胞壁硅化作用变化的证据。在含有硅藻和食草动物的预处理培养基中生长的细胞，其硅化程度明显高于在仅含有硅藻或饥饿食草动物的培养基中生长的硅藻。这些观察结果表明，摄食诱导的细胞壁硅化作用增强可被视为在摄食压力可变的生境中的一种适应性反应，并证明硅藻中的硅化作用不仅是对细胞的一种组成性机械保护，也是一种受摄食调节的表型可塑性特征。反过来，我们的结果证实了这样一种观点，即植物 - 食草动物相互作用，除了严格意义上的摄食之外，也有助于推动海洋生态系统结构和生物地球化学循环。
