Duffy J E, Paul V J
UOG Station, University of Guam Marine Laboratory, 96923, Mangilao, GU, USA.
Oecologia. 1992 Jun;90(3):333-339. doi: 10.1007/BF00317689.
Many coral-reef seaweeds and sessile invertebrates produce both secondary chemicals and mineral or fibrous skeletal materials that can reduce their susceptibility to consumers. Although skeletal materials often have been assumed to function as physical defenses, their deterrent effectiveness may derive from their reduction of prey nutritional quality as well as from noxiousness of the skeletal material itself. To test the relative importance of prey nutritional quality and chemical defenses in susceptibility to predation, we offered reef fishes on Guam a choice of artificial foods varying in nutritional quality (4% versus 22% protein) and in secondary chemistry (spanning approximately natural concentration ranges). Field feeding assays were performed with pachydictyol A from the pantropical brown seaweed genus Dictyota, manoalide from the Micronesian sponge Luffariella variabilis, and a brominated diphenyl ether from the Micronesian sponge Dysidea sp. The results indicated that chemical defenses were less effective in high- than in low-quality foods. In paired assays with metabolite-free controls, all three compounds at natural concentrations significantly reduced feeding by reef fishes only in assays using low-quality food, and not in assays with high-quality food. When fishes were offered an array of artificial foods varying in both food quality and metabolite concentration, food quality significantly affected fish feeding in all three cases, while secondary chemistry was significant in only one. Thus differences in nutritional quality, within the natural range among reef organisms, can be comparable to or greater in importance than secondary chemistry in affecting feeding preferences of their consumers. Reduced nutritional quality may be an important selective advantage of producing indigestible structural materials, in addition to their roles as physical support and defense, in coral reef organisms.
许多珊瑚礁海藻和固着无脊椎动物会产生次生化学物质以及矿物质或纤维状骨骼物质，这些物质可以降低它们对消费者的易感性。尽管骨骼物质通常被认为起到物理防御的作用，但其威慑效果可能源于其对猎物营养质量的降低以及骨骼物质本身的毒性。为了测试猎物营养质量和化学防御在被捕食易感性中的相对重要性，我们在关岛为珊瑚礁鱼类提供了营养质量不同（蛋白质含量4%与22%）以及次生化学性质不同（跨越大约自然浓度范围）的人工食物供其选择。我们用来自泛热带褐藻属网地藻的厚叶藻醇A、来自密克罗尼西亚海绵可变裸海绵的 manoalide以及来自密克罗尼西亚海绵瘤状海绵的一种溴化二苯醚进行了野外摄食试验。结果表明，化学防御在高质量食物中比在低质量食物中效果更差。在与无代谢物对照的配对试验中仅在使用低质量食物的试验中，而不是在高质量食物的试验中，所有三种化合物在自然浓度下都显著降低了珊瑚礁鱼类的摄食。当为鱼类提供一系列食物质量和代谢物浓度都不同的人工食物时，在所有三种情况下食物质量都显著影响鱼类摄食，而次生化学性质仅在一种情况下有显著影响。因此，在珊瑚礁生物自然范围内营养质量的差异在影响其消费者的摄食偏好方面可能与次生化学性质具有同等重要性或更重要。除了作为物理支撑和防御的作用外，营养质量的降低可能是珊瑚礁生物产生难消化结构物质的一个重要选择优势。
