Jönsson K Ingemar, Harms-Ringdahl Mats, Torudd Jesper
Department of Theoretical Ecology, Lund University, Sweden.
Int J Radiat Biol. 2005 Sep;81(9):649-56. doi: 10.1080/09553000500368453.
Tardigrades have a reputation of being extremely tolerant to extreme environmental conditions including tolerance to ionizing radiation while in a desiccated, anhydrobiotic state. However, the evidence for radio-tolerance in tardigrades is based on only one previous report, and there is an obvious need for complementary studies. In this paper we report an investigation on radio-tolerance in desiccated and hydrated specimens of the eutardigrade Richtersius coronifer.
Groups of 30 - 50 tardigrades were exposed to gamma-radiation at doses between 1.0 - 9.0 (anhydrobiotic animals) or 0.5 - 5.0 (hydrated animals) kGy and the animals were followed until all were dead. Radiation tolerance of both desiccated and hydrated tardigrades was studied.
Both desiccated and hydrated animals irradiated with 0.5 and 1 kGy did not deviate in survival from the control groups. Animals from all exposed groups underwent their moulting and egg production cycle, but at decreasing frequency for doses above 1 kGy. No eggs laid by irradiated animals hatched, while eggs laid by controls did so.
Our study suggests that radiation tolerance in tardigrades is not due to biochemical protectants connected with the desiccated state. Rather, cryptobiotic tardigrades may rely on efficient mechanisms of DNA repair, the nature of which is currently unknown.
缓步动物以对极端环境条件具有极强耐受性而闻名，包括在干燥的隐生状态下对电离辐射的耐受性。然而，缓步动物耐辐射性的证据仅基于之前的一份报告，显然需要进行补充研究。在本文中，我们报告了对真缓步动物冠状富氏熊虫干燥和水合标本耐辐射性的研究。
将30 - 50只缓步动物分为一组，分别接受1.0 - 9.0（隐生动物）或0.5 - 5.0（水合动物）千戈瑞剂量的伽马辐射，然后对这些动物进行跟踪观察，直至全部死亡。研究了干燥和水合缓步动物的辐射耐受性。
接受0.5和1千戈瑞辐射的干燥和水合动物的存活率与对照组相比没有偏差。所有暴露组的动物都经历了蜕皮和产卵周期，但对于剂量高于1千戈瑞的情况，其频率逐渐降低。受辐射动物所产的卵没有孵化，而对照组所产的卵则孵化了。
我们的研究表明，缓步动物的辐射耐受性并非源于与干燥状态相关的生化保护剂。相反，隐生的缓步动物可能依赖于目前尚不清楚其性质的高效DNA修复机制。
