Reduced gravity and muon radiation affect Caenorhabditis elegans life history traits and viral infection

Conditions beyond Earth —including gravitational forces and radiation exposure— often deviate substantially from those at the planet’s surface. In this study, we investigated the effects of reduced gravity (simulated through a Random Positioning Machine) and below-background radiation (primarily lowered muon flux in an underground facility) on Orsay virus infection in the nematode Caenorhabditis elegans . We employed a fully factorial experimental design, examining how each factor, alone and in combination, influences physiological traits and viral load. While below-background radiation increased viral accumulation, reduced gravity tended to decrease it. Both factors significantly impacted reproduction and morphology, with some effects magnified by viral infection. These results reveal how partial modifications of Earth-like gravity and radiation levels can alter pathogen–host interactions. Although this work does not encompass the full complexity of space environments —where cosmic radiation includes high-energy protons and heavy ions— it provides insight into how adjustable models of reduced gravity and radiation can advance our understanding of biological adaptation beyond standard terrestrial conditions.