| 1. |
- Jönsson, Ingemar, et al.
(författare)
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Tolerance to gamma-irradiation in eggs of the tardigrade Richtersius coronifer depends on stage of development
- 2013
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Ingår i: Journal of limnology. - : PAGEPress Publications. - 1129-5767 .- 1723-8633. ; 72, s. 73-79
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Guidetti, R, et al.
(författare)
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Long-term anhydrobiotic survival in semi-terrestrial micrometazoans
- 2002
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Ingår i: Journal of Zoology. - 0952-8369. ; 257:2, s. 181-187
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Tidskriftsartikel (refereegranskat)abstract
- This study represents the first systematic investigation of long-term anhydrobiotic survival in tardigrades, rotifers and nematodes inhabiting mosses and lichens. Sixty-three different samples from public and private collections, kept dry for 9-138 years, were examined. Rotifers of the genus Mniohia and the eutardigrade Ramazzottius oberhaeuseri (hatched from eggs) were found alive from one of the samples (9 years old). These observations represent the longest record for rotifers in the anhydrobiotic state. For tardigrades, our results confirm previous reports on the upper limit of anhydrobiotic survival under atmospheric oxygen conditions. This study suggests the possibility that tardigrade eggs are able to withstand longer periods in anhydrobiosis than animals. Some problems related to the evaluation of long-term anhydrobiotic survival, such as contamination and chemical treatments of samples, are reported. The possible role of the microenvironment in which the anhydrobiotic animals are kept is discussed.
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| 3. |
- Jönsson, Ingemar, et al.
(författare)
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Radiation tolerance in the eutardigrade Richtersius coronifer
- 2005
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Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 81:9, s. 649-656
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: 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 . Materials and methods: Groups of 30 – 50 tardigrades were exposed to γ-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. Results: 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. Conclusion: 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.
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