The brine shrimp Artemia franciscana as a model for astrobiological studies: Physiological adaptations to Mars-like atmospheric pressure conditions

Understanding the adaptation mechanisms of extremophiles to extreme environments is fundamental to predicting organisms' capacity to survive in space and plan future space exploration missions. This study explores the physiological and metabolic adaptations of nauplii of a eukaryotic organism, Artemia franciscana, hatched from cysts exposed to Mars-like pressure conditions (6 mbar) by analyzing aerobic and anaerobic metabolism, mitochondrial function, and oxidative stress in nauplii. Mars-like pressure did not inhibit nauplii's hatching or in vivo respiration, indicating that the fundamental metabolic functions are preserved but affected cellular metabolism. The lower lactate levels suggested reduced anaerobic metabolism, and the reduction in the activity of Complex I of the electron transport chain, resulting in reduced in vitro respiration supported by pyruvate plus malate, suggested an effect on aerobic metabolism. However, the succinate-supported respiration remained stable according to unchanged Complex II activity. Changes in aerobic metabolism could affect Reactive Oxygen Species (ROS) production and management. We did not observe changes in ROS levels according to the unchanged activity of NADPH oxidase, a source of ROS in the early development stages of nauplii. A total antioxidant capacity reduction and increased susceptibility to oxidants were observed despite this. However, lipid and protein oxidative stress markers levels remained unchanged, likely due to the increased activity of antioxidant enzymes. Our results underscore the resilience of the cysts to Mars-like pressure conditions, indicating the potential of Artemia franciscana as a model organism in astrobiological research, opening new avenues for exploration in astrobiology.