Two tardigrade species on board of the STS-134 space flight

The TARDIKISS project (Tardigrades in Space) investigated the physiological and molecular effects of space stresses on alive desiccated tardigrades, as representative of multicellular organisms. It has been a part of the BIOKIS (Biokon in Space), a set of multidisciplinary experiments of DAMA (DArk MAtter) mission on board of STS-134 space flight, the last of the shuttle Endeavour, in the frame of a joint between ASI and Italian Air Force. In TARDIKISS, experimentally desiccated (anhydrobiotic) specimens of Paramacrobiotus richtersi and Ramazzottius oberhaeuseri have been used. Both species have very good anhydrobiotic ability, but differ for several biological and ecological characters. The experiment units of TARDIKISS were hosted into the Biokon, a standard transportable container designed and manufactured by Kayser Italia. In May 2011, the Biokon containing the TARDIKISS experiment unit was integrated on Middeck Locker of ISS and had flown for 16 days at Low Earth Orbit. Two sample sets were used as controls: the former (Laboratory Control) was maintained in Modena laboratory for the duration of the flight, and the latter one (Temperature Control) was a post-flight control in which samples were exposed to the temperature profile experienced by tardigrades the days immediately before, during, and just after the flight mission. For both species, the flight animals did not show differences in survival with regards of Laboratory control and Temperature control animals. Only in R. oberhaeuseri differences have been recorded between Flight and Temperature Control samples. Live specimens of P. richtersi from Flight samples, Laboratory control and Temperature control samples have been reared in lab. Flight females laid eggs with normal shape; several eggs have been able to hatch, and newborns exhibited normal morphology, behaviour and capability to reproduce. Moreover, a comparative analyses of the antioxidant metabolism between Flight samples and Temperature control samples has been done. No differences have been evidenced between the two groups, with the exception of the reductase activity: significant differences in reductase activity between Flight and Temperature control were evidenced (p<0.05) in R. oberhaeuseri. These first results lead us to deduce that during the DAMA mission, microgravity and cosmic radiations did not significantly affect survival of flown tardigrades, confirming that tardigrades represent a useful animal tool for space research.