Smelling Danger – Alarm Cue Responses in the Polychaete Nereis (Hediste) diversicolor (Müller, 1776) to Potential Fish Predation

The harbour ragworm, Nereis (Hediste) diversicolor is a common intertidal marine polychaete that lives in burrows from which it has to partially emerge in order to forage. In doing so, it is exposed to a variety of predators. One way in which predation risk can be minimised is through chemical detection from within the relative safety of the burrows. Using CCTV and motion capture software, we show that H. diversicolor is able to detect chemical cues associated with the presence of juvenile flounder (Platichthys flesus). Number of emergences, emergence duration and distance from burrow entrance are all significantly reduced during exposure to flounder conditioned seawater and flounder mucous spiked seawater above a threshold with no evidence of behavioural habituation. Mucous from bottom-dwelling juvenile plaice (Pleuronectes platessa) and pelagic adult herring (Clupea harengus) elicit similar responses, suggesting that the behavioural reactions are species independent. The data implies that H. diversicolor must have well developed chemosensory mechanisms for predator detection and is consequently able to effectively minimize risk.港湾沙蚕（学名：Nereis (Hediste) diversicolor）是一类常见的潮间带海洋多毛类环节动物，它们栖息于洞穴内，需部分钻出洞穴方可觅食。在此过程中，它们会暴露于各类捕食者的威胁之下。降低捕食风险的途径之一，便是在相对安全的洞穴内部通过化学感知进行检测。本研究通过闭路电视（CCTV）与运动捕捉软件开展实验，结果表明杂色伪沙蚕（H. diversicolor）能够识别与幼欧鲽（Platichthys flesus）存在相关的化学信号。当处于阈值浓度以上的欧鲽驯养海水与添加欧鲽粘液的海水环境中时，沙蚕的钻出次数、钻出时长以及距洞穴入口的距离均显著降低，且未观察到行为习惯化现象。栖息于底栖的欧洲菱鲽幼鱼（Pleuronectes platessa）以及远洋成年大西洋鲱（Clupea harengus）所分泌的粘液，同样能引发类似的行为反应，这表明此类行为反应并非物种特异性的。上述实验结果表明，杂色伪沙蚕（H. diversicolor）具备完善的捕食者化学感知机制，因此能够有效降低自身遭遇捕食的风险。