Locomotion is considered to be the main form of expression of ciliate behaviour regarding their overall life activity. But how ciliates behave under deep-sea conditions is still unclear. Data on the occurrence of ciliates in the deep sea are scarce and mostly based on molecular studies. We isolated three different ciliates, Aristerostoma sp., Euplotes dominicanus and Pseudocohnilembus persalinus from two stations located in abyssal depths of the North Atlantic Ocean (≥ 4000 m; 15° 55.89′ N, 68° 53.34′ W; 23° 33.23′ N, 48° 5.04′ W) during the deep-sea expedition with the research vessel R/V Meteor (Cruise M139, 08.07.–08.08.2017). We observed their behaviour directly under high hydrostatic pressures up to 500 bar. The three ciliate species behaved normally up to a pressure of 200 bar, but showed disturbances of the normal behaviour at higher pressures. For all three isolated deep-sea ciliates, additional long-term survival experiments were carried out for 6 days at 200, 350 and 430 bar. Several specimens showed an ability to survive the entire experimental time interval at the highest pressure and to recover from pressure release (returning to their normal movement) indicating their barotolerance. Our results suggest that ciliates are active in the deep sea even in regions deeper than 2000 m and might be an important part of the deep-sea microbial food web.

中文翻译：

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静水压力对从深海海底分离的三种纤毛虫行为的影响

运动被认为是纤毛虫对其整体生活活动的主要表现形式。但纤毛虫在深海条件下的行为仍不清楚。关于深海纤毛虫出现的数据很少，主要基于分子研究。我们从位于北大西洋深海深处的两个站点（≥ 4000 m；15° 55.89' N，68° 53.34' W；23°, 33 48° 5.04′ W) 与研究船 R/V Meteor (Cruise M139, 08.07.–08.08.2017) 进行的深海探险。我们直接观察了它们在高达 500 bar 的高静水压力下的行为。三种纤毛虫物种在高达 200 巴的压力下表现正常，但在较高压力下表现出正常行为的干扰。对于所有三种分离的深海纤毛虫，在 200、350 和 430 巴下进行了 6 天的额外长期存活实验。几个样本显示出在最高压力下能够在整个实验时间间隔内存活并从压力释放（恢复正常运动）中恢复的能力，表明它们的气压耐受性。我们的研究结果表明，纤毛虫在深海中甚至在 2000 m 以上的区域也很活跃，并且可能是深海微生物食物网的重要组成部分。几个样本显示出在最高压力下能够在整个实验时间间隔内存活并从压力释放（恢复正常运动）中恢复的能力，表明它们的气压耐受性。我们的研究结果表明，纤毛虫在深海中甚至在 2000 m 以上的区域也很活跃，并且可能是深海微生物食物网的重要组成部分。几个样本显示出在最高压力下能够在整个实验时间间隔内存活并从压力释放（恢复正常运动）中恢复的能力，表明它们的气压耐受性。我们的研究结果表明，纤毛虫在深海中甚至在 2000 m 以上的区域也很活跃，并且可能是深海微生物食物网的重要组成部分。