Tardigrade behavioural studies have focused on responses to abiotic environmental conditions. Predator–prey interactions have received some attention, but not how predators and prey might detect one another. Here, we investigate whether a predatory tardigrade species is attracted to, and a potential prey tardigrade avoids, areas previously occupied by the other. In our experiments, Milnesium lagniappe was the predator and Macrobiotus acadianus the prey. Petri dishes with non-nutrient agar were used as experimental arenas. In one treatment, we allowed Macrobiotus to roam over half of the agar for 20 h, while leaving the other half free of Macrobiotus. We then removed the prey and introduced the predator. In the control treatment, no prey were added. Results indicated that Milnesium individuals were significantly concentrated in the area previously occupied by Macrobiotus, whereas no such concentration was evident when Macrobiotus had not been present. A similar protocol was used to test whether Macrobiotus avoided areas previously occupied by the predator. As expected, Macrobiotus were significantly concentrated in the area never occupied by Milnesium, unlike the control treatment. These results suggest that both species can detect the other without physical contact and react accordingly. Given that the experiments were conducted in darkness, detection is probably olfactory.

中文翻译：

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两种水熊（Tardigrada）中的捕食者和猎物检测

Tardigrade行为研究的重点是对非生物环境条件的响应。捕食者与猎物的相互作用已经引起了一定的关注，但掠食者和猎物如何相互检测却未引起注意。在这里，我们调查掠夺性的兽脚类物种是否被其他人先前占领的地区所吸引，并避免了它们的潜在猎物。在我们的实验中，拉尼米尔（Milnesium lagniappe）是捕食者，而Macrobiotus acadianus是猎物。具有非营养琼脂的培养皿用作实验场所。在一种处理中，我们允许Macrobiotus漫游一半以上的琼脂20小时，而另一半则不含Macrobiotus。然后，我们移除了猎物并引入了捕食者。在对照处理中，没有添加猎物。结果表明，Milnesium个体显著集中在先前由占据的面积Macrobiotus，而没有这样的浓度是明显的，当Macrobiotus不在场。使用类似的协议来测试Macrobiotus是否避开了先前被掠食者占据的区域。正如预期的那样，Macrobiotus明显集中在从未被Milnesium占据的区域，不同于对照治疗。这些结果表明，这两个物种都可以在没有物理接触的情况下检测到另一个，并做出相应的反应。由于实验是在黑暗中进行的，因此检测可能是嗅觉。