[You are receiving this message because your address came up in a specific literature search; it was not included in any mailing lists, and is used for a single advice. The information in this e-mail and in any attachments is confidential and intended solely for the attention and use of the named addressee(s). This information may be subject to legal, professional or other privilege and further distribution of it is strictly prohibited without our authority. If you are not the intended recipient, you are not authorised to and must not disclose, copy, distribute, or retain this message or any part of it, and should notify us immediately. This footnote also confirms that this email has been automatically scanned for the presence of computer viruses, profanities and certain file types].
Tolerance to gamma-irradiation in eggs of the tardigrade Richtersius coronifer depends on stage of development
Ingemar Jönsson, Eliana Beltran-Pardo, Siamak Haghdoost, Andrzej Wojcik, Rosa María Bermúdez-Cruz, Jaime E. Bernal Villegas, Mats Harms-Ringdahl
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.