Abstract
This work is a review of the experiments carried out in the Russian segment of the ISS (inside and outside) from 2005 to 2016 on the effect of the space flight factor on the resting stages of organisms. In outer space, ultraviolet, a wide range of high and low temperatures, cosmic radiation, altered gravity, modified electromagnetic field, vacuum, factors of technical origin, ultrasound, microwave radiation, etc. and their combination determine the damaging effect on living organisms. At the same time, biological dormancy, known in a wide range of bacteria, fungi, animals and plants, allows them to maintain the viability of their dormant stages in extreme conditions for a long time, which possibly allows them to survive during space flight. From 2005 to 2016, the resting stages (propagules) of micro- and multicellular organisms were tested on the ISS to assess their ability to survive after prolonged exposure to the conditions of open space and space flight. Among the more than 40 species studied, about a third were dormant stages of aquatic organisms (eggs of cyprinodont fish, daphnia embryos, resting eggs of fairy shrimps, tadpole shrimps, copepods and ostracods, diapausing larvae of dipterans, as well as resting cysts of algae). The experiments were carried out within the framework of four research programs: (1) inside the ISS with a limited set of investigated species (Akvarium program); (2) outside the station in outer space without exposure to ultraviolet radiation (Biorisk program); (3) under modified space conditions simulating the surface of Mars (Expose program); and (4) in an Earth-based laboratory where single-factor experiments were carried out with neutron radiation, modified magnetic field, microwave radiation and ultrasound. Fundamentally new data were obtained on the stability of the resting stages of aquatic organisms exposed to the factors of the space environment, which modified the idea of the possibility of bringing Earth life forms to other planets with spacecraft and astronauts. It also can be used for creating an extraterrestrial artificial ecosystem and searching for extraterrestrial life.
Highlights
Investigations to advance the use of animal and plant anabiosis, e.g., cryptobiosis and some other forms of dormancy, in space exploration highlight five notable programs on exobiology
Studies of the individual elements of the space flight factor that manifested themselves during intra-cabin transportation of the resting stages did not reveal a significant effect of each of the elements, considered separately, on the reactivation of embryos
The most significant was the effect of neutron radiation, which during the experiments did not affect the survival of the embryos, but undoubtedly was accepted by them, which led to a strong extension of the total reactivation period and a difference in the rate of hatching comparing with the control group
Summary
Investigations to advance the use of animal and plant anabiosis, e.g., cryptobiosis and some other forms of dormancy, in space exploration highlight five notable programs on exobiology. The increased viability of the diapausing stages of invertebrates and fish is based on a reduced level of the general metabolism of the organism and its related functions such as respiration, feeding, movement, etc., which are reduced to zero in the stages most deeply immersed in biological dormancy This determined the possibility of long-term (up to 2 years in the conducted experiments) maintenance of the viability of these stages in the atmosphere-deprived Biorisk and Expose-R modules on the outside of the ISS. The level of adaptive capabilities of active organisms is not comparable with the resting stages, and the mechanisms of adaptation to the SFF are radically different for them This determined the necessity of their separate study and consideration in the form of independent scientific directions [1,27]
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