To assess whether amphipods' habitat choice and feeding preference for a specific seaweed species are based on nutritional value or structural complexity, and to evaluate the role of chemical cues in the amphipod choice, we carried out laboratory experiments using amphipods (Ampithoe marcuzzii) and seaweeds from different divisions (Chlorophyta, Ochrophyta, and Rhodophyta). To evaluate feeding preference, we carried out a multiple-choice experiment offering six species of seaweeds to amphipods. To assess whether habitat choice by amphipods is guided exclusively by seaweed complexity, we conducted an assay offering seaweeds and complexity-like mimics (artificial plants) to amphipods, quantifying their choices. To evaluate whether seaweeds' secondary metabolites acted as chemical cues affecting seaweed choice by the amphipods, we used the same plastic mimics, one of which was brushed with crude extracts from the most-consumed seaweeds and a control. The consumption of Gracilaria cervicornis by amphipods was around three times higher than that of the other offered species, likely due to its paucity of chemical and physical defenses. The highest contents of nitrogen and crude proteins in this species may have contributed to its high consumption. Amphipods also used G. cervicornis as a shelter more than its mimic, but exhibited no preference between other seaweeds and their mimics, indicating that a more palatable refuge is preferred. This idea was corroborated when amphipods were able to detect chemical cues of G. cervicornis painted over a plastic mimic of similar structure and preferred it over the control mimic, which had the same complexity but no chemicals. Our results suggest that amphipods use chemical cues to identify high-quality habitat regarding refuge (complexity) and food source (nutritional value).

中文翻译：

---

食物来源或避难所：海藻片脚类动物选择背后的原因是什么？

为了评估片脚类动物对特定海藻物种的栖息地选择和摄食偏好是否基于营养价值或结构复杂性，并评估化学线索在片脚类动物选择中的作用，我们使用片脚类动物（Ampithoe marcuzzii) 和来自不同部门的海藻（绿藻门、绿藻门和红藻门）。为了评估摄食偏好，我们进行了一项多项选择实验，向片脚类动物提供六种海藻。为了评估片脚类动物的栖息地选择是否完全受海藻复杂性的指导，我们进行了一项分析，向片脚类动物提供海藻和类似复杂性的模拟物（人造植物），量化它们的选择。为了评估海藻的次生代谢物是否作为影响片脚类动物选择海藻的化学线索，我们使用了相同的塑料模拟物，其中一个用来自消耗最多的海藻和对照的粗提取物刷过。食用江蓠端足类动物的数量大约是其他物种的三倍，这可能是由于其缺乏化学和物理防御能力。该物种中最高含量的氮和粗蛋白质可能是其高消耗量的原因。片脚类动物也更多地使用G. cervicornis作为庇护所，而不是它的模仿者，但在其他海藻和它们的模仿者之间没有表现出偏好，这表明更可口的庇护所是首选。当片脚类动物能够检测到G. cervicornis 的化学线索时，这个想法得到了证实涂在类似结构的塑料模拟物上，并且比控制模拟物更喜欢它，后者具有相同的复杂性但没有化学物质。我们的结果表明，片脚类动物使用化学线索来识别关于避难所（复杂性）和食物​​来源（营养价值）的高质量栖息地。