Herbivory is a fundamental process regulating the functioning of the ecosystems both in land and marine systems. Few decades ago, herbivory was thought to play only a minor role in seagrass dominated areas, while currently its importance has risen. However, the complex interrelationships between seagrasses and their consumers are not yet fully understood. For instance, seagrasses can tune up morphological, biomechanical, nutritional, and chemical traits in order to reduce the palatability of their leaves and therefore curtail tissue losses, but the final tradeoff of such changes may depend on herbivore guilds. This work focuses on the relative importance of nutritional versus chemical traits in the feeding behavior of the sea urchin Paracentrotus lividus, a temperate generalist mesograzer, over two sympatric seagrass species (Cymodocea nodosa and Zostera noltei). To do that, a set of no-choice and multiple-choice feeding assays were conducted using freeze-dried plants agar-based diets (i.e. whole nutritional properties), polar extracts of both species (i.e. soluble sugars and phenolic natural products), purified phenolic natural products, and also three different concentrations of soluble sugars. Later, a chemical identification and quantification of the phenolic natural products present in the extracts were performed to assess their ecological role as deterrents. Results clearly indicated that the feeding behavior of this generalist herbivore, once overlooked the structural, morphological and biomechanical traits, is mainly determined by nutritional properties, while the presence of phenolic compounds has only a minimal effect on its feeding behavior. In addition, although this study showed that sugars had a positive effect over P. lividus consumption rates, we demonstrated for the first time the deterrent properties of rosmarinic acid and the sulphated flavonoids produced by Z. noltei, which were able to reduce the attractive effect of sugars in the feeding preference of this generalist herbivore.

食草是调节陆地和海洋系统生态系统功能的基本过程。几十年前，人们认为食草动物在海草占主导地位的地区只扮演次要角色，而现在它的重要性已经上升。然而，海草与其消费者之间复杂的相互关系尚未完全了解。例如，海草可以调整形态、生物力学、营养和化学特性，以降低其叶子的适口性，从而减少组织损失，但这些变化的最终权衡可能取决于食草动物行会。这项工作的重点是营养与化学特征在海胆Paracentrotus lividus摄食行为中的相对重要性, 温带通才 mesograzer, 超过两种同域海草物种 ( Cymodocea nodosa和Zostera noltei）。为此，使用冻干植物琼脂饲料（即全营养特性）、两种物种的极性提取物（即可溶性糖和酚类天然产物）、纯化的植物进行了一组无选择和多选择的喂养试验。酚类天然产物，以及三种不同浓度的可溶性糖。后来，对提取物中存在的酚类天然产物进行了化学鉴定和量化，以评估它们作为威慑物的生态作用。结果清楚地表明，这种多面食草动物的摄食行为，曾经被忽视了结构、形态和生物力学特征，主要由营养特性决定，而酚类化合物的存在对其摄食行为的影响很小。此外，P. lividus消耗率，我们首次证明了迷迭香酸和Z. noltei产生的硫酸化黄酮类化合物的威慑特性，它们能够降低糖对这种多面性食草动物的摄食偏好的吸引力。