Regeneration http://doi.org/b8hx (2017)
Planaria are flatworms that can regrow all of their body parts, even when cut into separate head, pharynx and tail segments, making them a popular model for regeneration studies. Now Junji Morokuma and co-workers are sending planaria into space to study their tissue growth in the absence of gravity and magnetic fields.
Samples of planaria both whole and amputated spent five weeks on board the International Space Station. Compared with the control group on Earth, a number of changes affected the space group: whole worms spontaneously fissioned (their way of asexual reproduction); they also altered their metabolism, as extra proteins were detected in their surrounding water; and most notably, one of the pharynx sections grew a head at either end. The double-headed phenotype is very rare, and might have had nothing to do with space travel. However, when the two-headed planarian was again cut into thirds, the headless segment grew two more heads, suggesting a persisting change in phenotype.
Of course the worms were cut on Earth and then loaded onto a rocket, where they experienced acceleration and altered temperature profiles compared to the control group. These differences need further study, with the worms cut in situ, in order to isolate the origin of any space-induced changes in morphology, growth or behaviour.