Marko P B, Palmer A R
Biol Bull. 1991 Dec;181(3):363-370. doi: 10.2307/1542356.
Laboratory experiments revealed that the rocky shore gastropod, Nucella lamellosa (Gmelin), could discriminate between the effluents of predatory and non-predatory crabs. N. lamellosa turned away from seawater that had passed over the large predatory crab, Cancer productus Randall. This avoidance behavior was observed in snails from two localities that, based on differences in shell form, presumably experienced different levels of predation intensity. The scent of the non-predatory crabs Pugettia producta (Randall) and Lopholithodes mandtii Brandt had no effect on the turning behavior of snails from either site. Surprisingly, snails from both sites were attracted to the scent of a small shore crab, Hemigrapsus nudus (Dana), but moved at random in response to a common prey item Balanus glandula Darwin. These results suggest that N. lamellosa can assess from a distance the relative risks posed by different species of crabs, and respond appropriately. The unexpected attraction to H. nudus suggests that N. lamellosa may use this effluent to home in from a distance on potential refugia, because H. nudus are often associated with crevices and the undersides of boulders where N. lamellosa would be less vulnerable to larger predators.
实验室实验表明，岩石海岸腹足纲动物，即紫贻贝（Nucella lamellosa，Gmelin），能够区分掠食性螃蟹和非掠食性螃蟹的排泄物。紫贻贝会避开经过大型掠食性螃蟹——太平洋黄道蟹（Cancer productus Randall）的海水。在来自两个地点的蜗牛中都观察到了这种回避行为，基于壳形的差异，推测这两个地点的蜗牛经历了不同程度的捕食强度。非掠食性螃蟹——太平洋扁平蟹（Pugettia producta，Randall）和曼氏拟石蟹（Lopholithodes mandtii Brandt）的气味对来自这两个地点的蜗牛的转向行为均无影响。令人惊讶的是，来自这两个地点的蜗牛都被一种小型海岸蟹——裸掌盾牌蟹（Hemigrapsus nudus，Dana）的气味所吸引，但对常见猎物——藤壶（Balanus glandula Darwin）的反应则是随机移动。这些结果表明，紫贻贝能够从远处评估不同种类螃蟹带来的相对风险，并做出适当反应。对裸掌盾牌蟹的意外吸引表明，紫贻贝可能利用这种排泄物从远处找到潜在的避难所，因为裸掌盾牌蟹通常与裂缝和巨石底部有关，而紫贻贝在这些地方受到大型捕食者攻击的可能性较小。
