Marine Laboratory, Queen's University Belfast, 12-13 The Strand, Portaferry, Northern Ireland BT22 1PF, UK.
Department of Earth and Planetary Science, University of California, Davis, CA 95616, USA.
Biol Lett. 2019 Oct 31;15(10):20190429. doi: 10.1098/rsbl.2019.0429. Epub 2019 Oct 2.
Many animals with external armour, such as hedgehogs, isopods and trilobites, curl into a protective ball when disturbed. However, in situations where predators would engulf an exposed animal whole, regardless of position, conglobation may provide limited added defence and the benefits were previously unclear. We show that polyplacophoran molluscs (chitons) are three times less likely to spend time curled into a ball in the presence of a predator. When the cue of a potential predator is present, animals instead spend significantly more time in active, high risk, high reward behaviours such as arching, balancing on the head and tail ends of their girdle and pushing the soft foot up into an exposed position. Arching increases vulnerability, but also can increase the likelihood of rapidly encountering new substratum that would allow the animal to right itself. In some other animals, the ability to roll into a ball is associated with rolling away from danger. Curling into a ball would improve mobility, to be rolled on to a safer position, but reattachment is the higher priority for chitons in the face of danger.
许多具有外部装甲的动物，如刺猬、等足类动物和三叶虫，在受到干扰时会卷曲成一个保护性的球。然而，在捕食者会不管位置如何，将暴露的动物整个吞下去的情况下，球形卷曲可能提供的额外防御有限，其好处之前并不清楚。我们表明，多板纲软体动物（石鳖）在有捕食者存在的情况下，蜷缩成球的时间减少了三分之一。当潜在捕食者的线索出现时，动物反而会花更多的时间进行积极的、高风险、高回报的行为，如拱起、在腰带的头部和尾部保持平衡，以及将柔软的脚推到暴露的位置。拱起会增加易受攻击的风险，但也可以增加遇到新基质的可能性，使动物能够自行恢复。在其他一些动物中，能够滚动成一个球与滚动远离危险有关。卷曲成一个球可以提高移动性，以便滚到一个更安全的位置，但在面临危险时，石鳖更优先考虑重新附着。
