Adineta vaga under fire: simulating the impact of radiation

Previous studies have demonstrated the remarkable resistance of bdelloid rotifers to ionizing radiation, making them an interesting model system for studying radiation effects on living organisms. In this study, we use simulations, instead of direct experimental exposures, to examine whether all bdelloids are affected equally by radiation exposure and to explore the relationship between biological data and energy deposition patterns induced by low and high linear energy transfer (LET) radiation. To this end, tool for particle simulation (TOPAS) a simulation tool, widely used in the field of medical physics and radiation therapy, was utilized. Using simulations for proton, iron ions, and X-ray exposure, our findings showed that all individuals, cells, and nuclei were effectively hit by the administered doses of 4 MeV protons, 0.5 GeV/n ⁵⁶Fe, and X-ray radiation. The results support that the impact on survival and fertility rate measured in Adineta vaga is caused by radiation-induced damage rather than the absence of hits in certain individuals or germinal cells. Notably, simulations revealed significant differences between low- and high-LET radiation concerning irradiated individuals' nuclei. Specifically, for an equivalent dose, high-LET radiation requires fewer incident particles compared to low-LET radiation, resulting in a sparser distribution of radiation hits on the nucleus surface. In conclusion, the study supports the idea that reduced fertility described in high-LET exposed samples is associated with complex DNA damage caused by the condensed energy deposition pattern of high-LET radiation compared to low-LET.