Tolerance to gamma-irradiation in eggs of the tardigrade Richtersius coronifer depends on stage of development
Tolerance to gamma-irradiation in eggs of the tardigrade Richtersius coronifer depends on stage of development
复制标题
缓步动物 Richtersius coronifer 卵对伽马射线的耐受性取决于发育阶段
DOI：
10.4081/jlimnol.2013.s1.e9
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发表时间：
2013
影响因子：
1.6
通讯作者：
M. Harms‐Ringdahl
中科院分区：
文献类型：
--
作者：
Ingemar Jönsson;Eliana Beltran;S. Haghdoost;A. Wójcik;R. Bermúdez;J. B. Villegas;M. Harms‐Ringdahl
缓步动物被认为是地球上最耐辐射的动物之一，已经发表了几项关于成年缓步动物耐受性的研究。相反，很少有关于胚胎阶段辐射耐受性的研究报道。在这里，我们报告了一项研究的耐受性，γ射线照射的真缓步类Richtersius coronifer的鸡蛋。直接从天然基质（苔藓）收集的卵的辐照显示出明显的剂量反应，在剂量高达0.4 kGy时孵化率急剧下降，随后在剂量高达2 kGy时孵化率相对恒定，约为25%，并下降至约20%。在4kGy剂量下为5%，超过此剂量则无卵孵化。对辐照后卵孵化所需时间（剩余发育时间）的分析表明，卵在受到高剂量伽马辐照后孵化与剩余发育时间短有关。由于剩余发育时间短意味着卵子在发育后期受到辐射，这表明卵子在发育后期对辐射的耐受性更强。这一点也在另一个实验中得到证实，在该实验中，辐照时的发育阶段受到控制。在早期发育阶段没有卵孵化，只有一个卵在中期阶段孵化，而在后期阶段照射的卵孵化率与对照无区别。这表明卵在发育的早期阶段对辐射更敏感，或者对辐射的耐受性只是在发育的后期，即卵孵化前不久才获得，这些假设并不相互排斥。我们的研究强调了在缓步动物的辐射耐受性研究中考虑特定细胞周期阶段和发育阶段的重要性，以及胚胎研究在揭示缓步动物和其他隐生物动物的辐射耐受性背后的机制中的潜在重要性。
Tardigrades are known as one of the most radiation tolerant animals on Earth, and several studies on tolerance in adult tardigrades have been published. In contrast, very few studies on radiation tolerance of embryonic stages have been reported. Here we report a study on tolerance to gamma irradiation in eggs of the eutardigrade Richtersius coronifer. Irradiation of eggs collected directly from a natural substrate (moss) showed a clear dose-response, with a steep decline in hatchability at doses up to 0.4 kGy followed by a relatively constant hatchability around 25% up to 2 kGy, and a decline to ca. 5% at 4 kGy above which no eggs hatched. Analysis of the time required for eggs to hatch after irradiation (residual development time) showed that hatching of eggs after exposure to high doses of gamma radiation was associated with short residual development time. Since short residual development time means that the egg was irradiated at a late developmental stage, this suggests that eggs were more tolerant to radiation late in development. This was also confirmed in another experiment in which stage of development at irradiation was controlled. No eggs irradiated at the early developmental stage hatched, and only one egg at middle stage hatched, while eggs irradiated in the late stage hatched at a rate indistinguishable from controls. This suggests that the eggs are more sensitive to radiation in the early stages of development, or that tolerance to radiation is acquired only late in development, shortly before the eggs hatch, hypotheses that are not mutually exclusive. Our study emphasizes the importance of considering specific cell cycle phases and developmental stages in studies of tolerance to radiation in tardigrades, and the potential importance of embryonic studies in revealing the mechanisms behind the radiation tolerance of tardigrades and other cryptobiotic animals.