Schnitzler Iris, Pohnert Georg, Hay Mark, Boland Wilhelm
Max-Planck-Institut für Chemische Ökologie, Carl-Zeiss-Promenade 10, 07745, Jena, Germany.
School of Biology, Georgia Institute of Technology, 30332-0230, Atlanta, GA, USA.
Oecologia. 2001 Feb;126(4):515-521. doi: 10.1007/s004420000546. Epub 2001 Feb 1.
Terpenoids, polyphenols, and C metabolites are broadly distributed among brown seaweeds. Terpenoids and polyphenols have often been investigated as chemical defenses against herbivores, while there are only few investigations of the fatty-acid-derived C hydrocarbons and C sulfur compounds as potential defenses. We investigated effects of C sulfur metabolites from the cosmopolitan brown alga Dictyopteris membranacea on feeding and fitness of the herbivorous amphipod Ampithoe longimana. In choice tests between freshly collected thalli of D. hoytii (which lacks C sulfur compounds) and D. membranacea (which contains C sulfur compounds) amphipods consumed about 4 times more of the species lacking the C sulfur compounds. The same feeding preference was observed when these plants were finely ground and embedded in an agar matrix to destroy morphological differences. When a diet made from field-collected thalli of D. membranacea containing C sulfur compounds was tested against a diet made from a laboratory culture of D. membranacea that had lost the ability to produce C sulfur compounds, the same magnitude of preference was observed for the population lacking the sulfur compounds. In addition to the C sulfur compounds, a water-soluble C9-oxo acid that appears to be a by-product in the biosynthesis of the C metabolites also suppressed amphipod feeding to a comparable extent. Both classes of compound may contribute to the effective chemical protection of D. membranacea. When juvenile amphipods were reared for 28 days on artificial diets containing the above compounds, their survivorship (≤10%) closely resembled that of a starved treatment, but differed dramatically from a control treatment (60%) consisting of the same food, but without the metabolites. Most other classes of brown algal secondary metabolites are defensive against a broad spectrum of larger herbivores, but relatively ineffective against the amphipod studied here. In contrast, the fatty-acid-derived sulfur compounds and the C9-oxo acid strongly deter Ampithoe-like mesograzers but appear less effective against other herbivores, suggesting that these metabolites could be ecologically important in defending zygotes and germlings against these small consumers.
萜类化合物、多酚和含碳代谢物广泛分布于褐藻中。萜类化合物和多酚常被作为对食草动物的化学防御机制进行研究，而关于脂肪酸衍生的碳氢化合物和碳硫化合物作为潜在防御机制的研究却很少。我们研究了全球分布的褐藻膜网翼藻中碳硫代谢物对草食性双足虾长肢长臂虾摄食和健康状况的影响。在新鲜采集的霍氏网翼藻（不含碳硫化合物）和膜网翼藻（含碳硫化合物）的藻体之间进行的选择试验中，双足虾对不含碳硫化合物的藻体的消耗量约为含碳硫化合物藻体的4倍。当将这些植物磨碎并嵌入琼脂基质以消除形态差异时，也观察到了相同的摄食偏好。当用含有碳硫化合物的野外采集的膜网翼藻藻体制成的食物与由失去产生碳硫化合物能力的膜网翼藻实验室培养体制成的食物进行测试时，对缺乏硫化合物的群体观察到了相同程度的偏好。除了碳硫化合物外，一种水溶性的C9 - 氧代酸似乎是含碳代谢物生物合成中的副产物，它也能在相当程度上抑制双足虾的摄食。这两类化合物可能都有助于膜网翼藻的有效化学保护。当幼年双足虾在含有上述化合物的人工饲料上饲养28天时，它们的存活率（≤10%）与饥饿处理的存活率非常相似，但与由相同食物但不含代谢物的对照处理（60%）有显著差异。大多数其他种类的褐藻次生代谢物对广泛的大型食草动物具有防御作用，但对这里研究的双足虾相对无效。相比之下，脂肪酸衍生的硫化合物和C9 - 氧代酸强烈地阻止了类似长臂虾的中层食草动物，但对其他食草动物的作用似乎较小，这表明这些代谢物在保护合子和幼苗免受这些小型消费者的侵害方面可能具有重要的生态意义。
