Institute of Biological Problems of the North, Far East Branch, Russian Academy of Sciences, Magadan, 685000, Russia.
Research Institute of Biology and Biophysics, Tomsk State University, Tomsk, 634050, Russia.
Sci Rep. 2019 Jan 10;9(1):13594. doi: 10.1038/s41598-018-31974-6.
Few of the amphibian species that occur in the Subarctic and in mountains are adapted to low sub-zero temperatures; most of these species overwinter underwater. It is believed that the distribution of the species that overwinter underwater can be limited by the low oxygen levels in waterbodies covered with ice. We show that the colonisation of the coldest areas of Northern Asia (to 71°N) by the Siberian wood frog (Rana amurensis) was facilitated by a unique adaptation, the ability to survive extreme hypoxia - and probably anoxia - in waterbodies during overwintering. The oxygen content in the overwintering waterbodies that we have studied in different parts of the range of this species fell to 0.2-0.7 mg/L without causing any large-scale mortality among the frogs. In laboratory experiments the R. amurensis survived for up to 97 days in hermetically sealed containers with water that contained less than 0.2 mg/L oxygen at temperatures of 2-3 °C, retaining the ability to respond to external stimuli. An earlier study of a broad range of frog species has shown that very few of them can survive even brief (up to 5-7 days) exposure to oxygen-free water. The revealed adaptation to prolonged extreme hypoxia is the first known case of this kind among amphibians overwintering in water.
在亚北极和高山地区生存的少数几种两栖物种能够适应零下的低温；这些物种中的大多数在水下过冬。人们认为，在被冰覆盖的水体中，能够适应水下过冬的物种的分布可能会受到低氧水平的限制。我们的研究表明，西伯利亚林蛙（Rana amurensis）通过一种独特的适应能力——在水下过冬期间能够在极端缺氧（甚至可能是无氧）条件下生存——得以在北亚最寒冷的地区（北纬 71°）定居。我们在该物种分布的不同地区研究了越冬水体的含氧量，结果表明，这些水体中的含氧量降至 0.2-0.7mg/L，而不会导致青蛙大规模死亡。在实验室实验中，林蛙在密封的容器中可以存活长达 97 天，这些容器中的水含氧量低于 0.2mg/L，温度为 2-3°C，且保持对外界刺激的反应能力。对广泛的蛙类物种的早期研究表明，它们中很少有物种能够在无氧水中存活哪怕短短几天。这种适应长时间极端缺氧的能力在水下过冬的两栖动物中尚属首例。
