Scientists studying flatworms that were part of a five-week experiment aboard the International Space Station (ISS) have found that absence of normal gravity can affect anatomy, behaviour and microbiology, especially their ability to regenerate.

The research has implications for human and animal space travellers and for regenerative and bioengineering science.

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A set of planarian flatworms (D. japonica) were launched into space via SpaceX Commercial Resupply Service Mission 5 on January 10, 2015.

These flatworms — known for their ability to regenerate when parts of their bodies are amputated — were either left whole or amputated and sealed in tubes filled half with water and half with air.

"During regeneration, development and cancer suppression, body patterning is subject to the influence of physical forces, such as electric fields, magnetic fields, electromagnetic fields, and other biophysical factors. We want to learn more about how these forces affect anatomy, behaviour and microbiology," said Michael Levin, Professor at Massachusetts-based Tufts University.

The findings, to be published in the journal Regeneration, showed that one of the amputated fragments sent to space was regenerated into a rare double-headed worm. 

Moreover, when the researchers amputated both heads from the space-exposed worm, the headless middle fragment regenerated into a double-headed worm, demonstrating that the body plan modification that occurred in the worm was permanent.

Additionally, whole worms sent into space underwent spontaneous fission — division of the body into two or more identical individuals — while their earth-bound counterparts did not. 

Further, when transferred to fresh spring water, the stay-at-home worms exhibited normal behaviour, while the 10 whole worms that had spent time in space curled up and were partially paralysed and immobile. 

The behaviour suggests that the worms had altered their biological state to accommodate the environmental change of being in space, reacting strongly to a return to normal aqueous conditions.

The worm groups also exhibited differences in their reaction to light. Furthermore, exposure to space also induced distinct differences in metabolism and/or secretion of these flatworms.

"As humans transition toward becoming a space-faring species, it is important that we deduce the impact of space flight on regenerative health for the sake of medicine and the future of space laboratory research," added Junji Morokuma, Research Associate at Tufts University.