title: Effects of ionizing radiation on embryos of the tardigrade Milnesium cf. tardigradum at different stages of development.
abstract: Tardigrades represent one of the most desiccation and radiation tolerant animals on Earth, and several studies have documented their tolerance in the adult stage. Studies on tolerance during embryological stages are rare, but differential effects of desiccation and freezing on different developmental stages have been reported, as well as dose-dependent effect of gamma irradiation on tardigrade embryos. Here, we report a study evaluating the tolerance of eggs from the eutardigrade Milnesium cf. tardigradum to three doses of gamma radiation (50, 200 and 500 Gy) at the early, middle, and late stage of development. We found that embryos of the middle and late developmental stages were tolerant to all doses, while eggs in the early developmental stage were tolerant only to a dose of 50 Gy, and showed a declining survival with higher dose. We also observed a delay in development of irradiated eggs, suggesting that periods of DNA repair might have taken place after irradiation induced damage. The delay was independent of dose for eggs irradiated in the middle and late stage, possibly indicating a fixed developmental schedule for repair after induced damage. These results show that the tolerance to radiation in tardigrade eggs changes in the course of their development. The mechanisms behind this pattern are unknown, but may relate to changes in mitotic activities over the embryogenesis and/or to activation of response mechanisms to damaged DNA in the course of development.
authors.affiliation: Instituto de Genética Humana, Pontificia Universidad Javeriana, Bogotá, Colombia ; Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
authors.forename: Eliana
authors.initials: E
authors.lastname: Beltrán-Pardo
authors.forename: K Ingemar
authors.initials: KI
authors.lastname: Jönsson
authors.forename: Andrzej
authors.initials: A
authors.lastname: Wojcik
authors.forename: Siamak
authors.initials: S
authors.lastname: Haghdoost
authors.forename: Mats
authors.initials: M
authors.lastname: Harms-Ringdahl
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Bermúdez-Cruz
authors.forename: Jaime E
authors.initials: JE
authors.lastname: Bernal Villegas
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000528:radiation effects*; D005720:Gamma Rays; D010063:Ovum / Q000528:radiation effects; D011836:Radiation Tolerance; D058467:Tardigrada / Q000166:cytology / Q000196:embryology / Q000528:radiation effects*
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 2010 Jun;156(2):115-21
references.pmid: 20206711
references.citation: PLoS One. 2012;7(9):e45682
references.pmid: 23029181
references.citation: Curr Biol. 2004 Jan 6;14(1):R35-45
references.pmid: 14711435
references.citation: Comp Biochem Physiol A Mol Integr Physiol. 2009 Aug;153(4):425-9
references.pmid: 19361569
references.citation: Astrobiology. 2012 Apr;12(4):283-9
references.pmid: 22490117
references.citation: Acta Physiol (Oxf). 2011 Jul;202(3):409-20
references.pmid: 21251237
references.citation: J Exp Biol. 2004 Apr;207(Pt 10):1607-13
references.pmid: 15073193
references.citation: Int J Radiat Biol. 2006 Dec;82(12):843-8
references.pmid: 17178624
references.citation: PLoS One. 2010 Nov 16;5(11):e14008
references.pmid: 21103355
references.citation: J Cell Sci. 2005 Aug 1;118(Pt 15):3305-15
references.pmid: 16079276
references.citation: Comp Biochem Physiol A Mol Integr Physiol. 2010 May;156(1):151-5
references.pmid: 20116441
references.citation: Curr Biol. 2008 Sep 9;18(17):R729-R731
references.pmid: 18786368
references.citation: Dev Biol. 2007 Dec 15;312(2):545-59
references.pmid: 17996863
references.citation: Int J Radiat Biol. 2005 Sep;81(9):649-56
references.pmid: 16368643
references.citation: Genetics. 2006 Jul;173(3):1301-17
references.pmid: 16702421
references.citation: PLoS One. 2010 Mar 03;5(3):e9502
references.pmid: 20224743
references.citation: J Insect Physiol. 2011 May;57(5):567-76
references.pmid: 21402076
references.citation: Radiat Res. 2008 Jun;169(6):707-11
references.pmid: 18494545
references.citation: J Insect Physiol. 2011 May;57(5):577-83
references.pmid: 21440551
references.citation: Reproduction. 2007 Feb;133(2):415-22
references.pmid: 17307909
references.citation: Evol Dev. 2003 Jan-Feb;5(1):83-8
references.pmid: 12492414
references.citation: Physiol Biochem Zool. 2003 Jul-Aug;76(4):429-35
references.pmid: 13130423
references.citation: Proc Natl Acad Sci U S A. 2008 Apr 1;105(13):5139-44
references.pmid: 18362355
references.citation: Zoolog Sci. 2003 Jan;20(1):49-57
references.pmid: 12560601
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 2007 Apr;146(4):456-60
references.pmid: 17261378
references.citation: J Cell Biol. 2006 Mar 27;172(7):999-1008
references.pmid: 16549501