Volume 23 (2009) Issue 2 Pages 61-69
The authors have a plan to examine the biological effects of cosmic rays by loading the eggs of the silkworm, Bombyx mori, in the International Space Station (ISS) for 3 months. In advance of the project, several ground experiments have been performed. In order to investigate the biological effects of radiation, heavy ion particles were used instead of cosmic rays. Heterozygous eggs of the black-striped strain (pS/p) were irradiated with Carbon (C), Neon (Ne) or Ferrous (Fe) ion particles. At the fifth instar stage, larvae that hatched from these eggs showed white spots on their backs against the black or dark brown of their integument. These are somatic mutations which seem to be caused by the effects of radiation on the pS gene. The incidence of this somatic mutation increased in proportion to dose and linear energy transfer of C and Ne ion particles, and it was higher after resumption of embryogenesis in eggs that had been irradiated after diapause termination as compared with eggs irradiated while still in diapause. Irradiation by more than 0.04 Gy of Fe ion particles to diapause-terminated eggs induced a significant incidence of somatic mutation compared with controls (P<0.05). Furthermore, radiation effects were also detected at the next generation as detected by egg color mutations by using the specific locus method. In experiments investigating the effects of microgravity on silkworm embryogenesis in the US Space Shuttle/Atlantis (STS-84) in 1997, we had observed that microgravity could influence embryonic reversal, presumably resulting in abnormal development of embryos. On the basis of the results from STS-84 flight and the above mentioned ground experiments, the authors will examine the interrelationship between the dose of cosmic rays and the incidence of somatic mutation, as well as confirm and extend the analysis of synergistic effects between cosmic rays and microgravity on mutation rates in experiments conducted using the ISS. These data will provide fundamental information on the effects of cosmic rays on biological systems that can then be applied to better protect humans against cosmic radiation during space flight.