Abstract
Interest in space habitation has grown dramatically with planning underway for the first human transit to Mars. Despite a robust history of domestic and international spaceflight research, understanding behavioral adaptation to the space environment for extended durations is scant. Here we report the first detailed behavioral analysis of mice flown in the NASA Rodent Habitat on the International Space Station (ISS). Following 4-day transit from Earth to ISS, video images were acquired on orbit from 16- and 32-week-old female mice. Spaceflown mice engaged in a full range of species-typical behaviors. Physical activity was greater in younger flight mice as compared to identically-housed ground controls, and followed the circadian cycle. Within 9–11 days after launch, younger (but not older), mice began to exhibit distinctive circling or ‘race-tracking’ behavior that evolved into a coordinated group activity. Organized group circling behavior unique to spaceflight may represent stereotyped motor behavior, rewarding effects of physical exercise, or vestibular sensation produced via self-motion. Affording mice the opportunity to grab and run in the RH resembles physical activities that the crew participate in routinely. Our approach yields a useful analog for better understanding human responses to spaceflight, providing the opportunity to assess how physical movement influences responses to microgravity.
Highlights
Interest in space habitation has grown dramatically with planning underway for the first human transit to Mars
We first determined whether the RR1 Video image resolution was sufficient for behavioral analysis by quantifying lens visibility in each of the www.nature.com/scientificreports bisected Validation and Experimental Rodent Habitat (RH) units across flight days for both flight and ground views (Fig. 1c,d)
Experimental group visibility on the earlier final video acquisition day (L + 20) was 67 and 77 percent for the left and right views. Since these groups were flown in the same RH hardware, and the Experimental mice were twice the age of the Validation mice, the 32 percent greater biomass of the Experimental relative to Validation Flt mice (Pre-Launch body mass (g) Mean +/− SD, Experimental, 28.8 +/− 2.0; Validation, 19.5 +/− 1.1) likely accounts for the approximately two times more rapid decline to a lower final percent visibility relative to Validation mice. This analysis reveals that the RH habitat design and Filter area video configuration provide excellent visibility and quality Video images that are amenable to highly detailed behavioral analysis for extended missions
Summary
We report the first detailed behavioral analysis of mice flown in the NASA Rodent Habitat on the International Space Station (ISS). We present a detailed behavioral analysis of mice living in space for extended durations (up to 37 days) as part of the NASA Rodent Research-1 (RR1) mission, the first deployment of the NASA Rodent Habitat on the ISS. Behavioral analysis can reveal how animals acclimate to the space environment, and how altered physical activity, feeding, Space Technologies, Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO, 80302, USA. Cage environment exerts major effects on rodent physiology and behavior[3,4] These concerns are magnified in the weightless space environment where an animal’s interactions with its habitat and conspecifics are dramatically altered compared to 1 g conditions. Physical activity, shaped by habitat configuration and complexity, can affect a broad range of physiological parameters - heart rate, respiration, oxygenation, and blood flow among others - that may in turn affect morphology, biochemistry, gene expression, or other physiological measures derived from body tissues
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