Bearing Extremes: Impacts from Simulated Outer Space Conditions and Effective Ultraviolet Radiation Shielding Materials on Tardigrade Life History

ABSTRACT: Questions about astrobiological resilience, whether entities with evolutionary histories on Earth would survive in outer space or on distant planets, for instance, no longer reside exclusively in the science fiction realm. In this study, we assess life history characteristics for individuals in the tardigrade species Grevenius annulatus post exposure to simulated outer space conditions with nonionizing radiation as a proxy for anticipated oxidative stress and damage incurred from exposure to full-spectrum environmental radiation. Using a planetary environment simulator, we exposed unshielded and shielded specimens to UVB and UVC radiation for 30 min and monitored and recorded subsequent life history characteristics. Survivorship was lower in an unshielded group relative to control as well as Kevlar and polyethylene shielded groups, demonstrating that Kevlar and polyethylene reduce impact from these types of nonionizing radiation, which are not expected to fully penetrate the shields. Cumulative egg production was lowest in the unshielded group, but egg viability and average egg production rate was highest. Due to insignificant differences, additional research to determine the relative effectiveness for Kevlar and polyethylene as shielding materials from survivorship and reproduction perspectives is warranted. This work provides a progressive step from which important conditions excluded in the current study, like vibrations, temperatures, debris-impacts, and ionizing radiation, can be included in future studies.