slower emergence of young fish from smaller, and thus weaker, embryos. The effect of
spaceflight factors is also manifested in the second generation of Daphnia, causing a transition
to gamogenesis and the production of males in the population. The D. magna embryos after
exposure on the ISS manifested a high sensitivity to the effect of the fungal parasite Pitium
daphniarum as compared to the control, which among other factors raises the question of
biological safety measures from spacecraft flora regarding biological material intended for long-
term space transportation.
In S. torvicornis, a decrease in growth and reproduction parameters was observed, however,
unlike the control, this was not confirmed statistically due to extremely high variability and
relating to its parameter assessment error. The only statistically significant factor for this
species was the effect of day length on the growth of females.
The studies of Artemia salina showed that the temperature threshold of expression activation
of the gene encoded in the Hsp90 molecular chaperone was substantially lower in response to
thermal stress in Artemia nauplius from the flight samples than in the ground control group.
This manifested as a sharp increase detected in the level of Hsp90 gene expression in both
flight groups with thermal stress of 32-33°C, while in the control groups the minimum thermal
stress required to initiate Hsp90 synthesis was 37-38°C.
Investigations on the ground did not identify an impact of spaceflight factors on the rate of
reactivation and subsequent vital activity on the chironomid Polypedilum vanderplanki larva
exposed on the ISS in a state of cryptobiosis. The fertility in the experiment animals did not
differ from that of the control animals.
These results showed that a cell in a dormant stage and containing just 5% water is capable of
acquiring and transferring information on the effects of negative factors after transitioning
Daphnia magna female (A) and male (B). Roscosmos image.