Species of littoral freshwater environments in regions with continental climate experience pronounced seasonal temperature changes. Coping with long cold winters and hot summers requires specific physiological and behavioural adaptations. Endemic amphipods of Lake Baikal, Eulimnogammarus verrucosus and Eulimnogammarus cyaneus, show high metabolic activity throughout the year; E. verrucosus even reproduces in winter. In contrast, the widespread Holarctic amphipod Gammarus lacustris overwinters in torpor. This study investigated the transcriptomic hallmarks of E. verrucosus, E. cyaneus and G. lacustris exposed to low water temperatures. Amphipods were exposed to 1.5°C and 12°C (corresponding to the mean winter and summer water temperatures, respectively, in the Baikal littoral) for one month. At 1.5°C, G. lacustris showed upregulation of ribosome biogenesis and mRNA processing genes, as well as downregulation of genes related to growth, reproduction and locomotor activity, indicating enhanced energy allocation to somatic maintenance. Our results suggest that the mitogen‑activated protein kinase (MAPK) signalling pathway is involved in the preparation for hibernation; downregulation of the actin cytoskeleton pathway genes could relate to the observed low locomotor activity of G. lacustris at 1.5°C. The differences between the transcriptomes of E. verrucosus and E. cyaneus from the 1.5°C and 12°C exposures were considerably smaller than for G. lacustris. In E. verrucosus, cold-exposure triggered reproductive activity was indicated by upregulation of respective genes, whereas in E. cyaneus, genes related to mitochondria functioning were upregulated, indicating cold compensation in this species. Our data elucidate the molecular characteristics behind the different adaptations of amphipod species from the Lake Baikal area to winter conditions.

中文翻译：

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玩酷的不同方式：转录组学分析揭示了三种端足类动物在长期寒冷环境下的不同活动模式

大陆性气候地区的沿海淡水环境物种经历明显的季节性温度变化。应对漫长的寒冷冬季和炎热的夏季需要特定的生理和行为适应。贝加尔湖特有的端足类动物，疣状毛蚴和蓝毛蚴，全年都表现出高代谢活动；E. verrucosus甚至在冬天繁殖。相比之下，广泛分布的全北极片脚类动物Gammarus lacustris在麻木中越冬。本研究调查了疣状大肠杆菌、蓝绿色大肠杆菌和紫球藻的转录组学特征。暴露于低水温。片足类动物在 1.5°C 和 12°C（分别对应于贝加尔湖沿岸的冬季和夏季平均水温）中暴露了一个月。在 1.5°C 时，G .  lacustris显示核糖体生物发生和 mRNA 加工基因的上调，以及与生长、繁殖和运动活动相关的基因的下调，表明对体细胞维持的能量分配增强。我们的结果表明，有丝分裂原活化蛋白激酶（MAPK）信号通路参与了冬眠的准备。肌动蛋白细胞骨架通路基因的下调可能与观察到的G的低运动活性有关。 湖水在 1.5°C。E. verrucosus和E. cyaneus在 1.5°C 和 12°C 暴露下的转录组差异远小于G. lacustris。在E中。 verrucosus，冷暴露引发的生殖活动由各自基因的上调表明，而在E。 cyaneus，与线粒体功能相关的基因被上调，表明该物种的冷补偿。我们的数据阐明了贝加尔湖地区片脚类动物对冬季条件的不同适应背后的分子特征。