Researchers sent flatworms aboard the International Space Station for five weeks to study how an absence of normal gravity can affect behavior and anatomy - in particular, their ability to regenerate missing parts.

Flatworms were either left whole or amputated, and most surprisingly, one of the amputated fragments regenerated into a double-headed worm.

When the researchers amputated both heads, they also discovered the headless middle fragment regenerated into another double-headed worm.

Scroll down for video

An amputated flatworm fragment sent to space regenerated into a double-headed worm, a rare occurrence. When the researchers amputated both heads from the space-exposed worm, the headless middle fragment regenerated into another double-headed worm

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

The research, led by the Allen Discovery Center at Tufts University, was conducted to study how an absence of normal gravity and geomagnetic fields can have anatomical, behavioral and bacteriological consequences.

The researchers chose to study planarian flatworms (Dugesia japonica), which are often used for studies because of their ability to regenerate when part of their bodies are amputated.

They launched a set of flatworms into space via SpaceX Commercial Resupply Service Mission 5, on January 10, 2015.

Knowing what happens to them in space and upon their return to Earth could lead to a better understanding of how physical forces, such as microgravity and micro-geomagnetic fields, influence growth, body shape and cellular decision-making.

'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,' says Dr Michael Levin, Vannevar Bush professor of biology and director of the Allen Discovery Center at Tufts University, and the corresponding author of the study.

HOW THEY DID THE STUDY Researcher at Tufts University chose to study planarian flatworms (Dugesia japonica), which are often used for studies because of their ability to regenerate when part of their bodies are amputated. They launched a set of flatworms into space via SpaceX Commercial Resupply Service Mission 5, on January 10, 2015. The flatworms launched into space were either left whole or amputated and sealed in tubes filled half with water and half with air. The researchers also created two sets of control worms that stayed on Earth. One set was live and sealed in spring water in the same manner as their space counterparts and kept in darkness at 20 degrees Celsius for the same amount of time. (A) 15 flatworms were cut in thirds and collected in separate tubes. (B) Identical numbers of worm samples, both whole and amputated fragments, were either sent to space or stayed on Earth for 32 days. (C) On return to Earth, all samples were analyzed After the space exposed worms returned to Earth, researchers prepared a second set of worms that were exposed to the same changes in temperature as the space-exposed worms. After five weeks in space, the samples were returned and analyzed for 20 months. After a range of tests, the researchers identified a number of differences between the space and terrestrial worms. Advertisement

'We want to learn more about how these forces affect anatomy, behavior and microbiology,' said Dr Levin.

'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,' said Dr Junji Morokuma, a research associate in Dr Levin's lab and first author on the study.

The flatworms launched into space were either left whole or amputated and sealed in tubes filled half with water and half with air.

The researchers also created two sets of control worms.

In the experiment, the head of a double-headed 'space worm' was amputated on both sides (A&B). This revealed that after amputation (C), both heads grew back by the time two weeks had passed - and the headless fragments also each grew a head (D). A closeup is shown (E,F)

One set was live and sealed in spring water in the same manner as their space counterparts and kept in darkness at 20 degrees Celsius for the same amount of time.

After the space exposed worms returned to Earth, researchers prepared a second set of worms that were exposed to the same changes in temperature as the space-exposed worms.

After five weeks in space, the samples were returned and analyzed for 20 months.

After a range of tests, the researchers identified a number of differences between the space and terrestrial worms.

According to the researchers, the most surprising finding was that one of the amputated fragments sent to space regenerated int a rare double-headed worm.

In more than 18 years of maintaining a colony of more than 15,000 control worms in just the last five years, the Tufts researchers have never observed a spontaneous occurrence of double-headedness.

When the researchers amputated both heads from the space-exposed worm, the headless middle fragment regenerated into another double-headed worm, showing that the body plan modification that occurred in the worm was permanent.

The researchers also found that whole worms sent into space underwent spontaneous fission - division of the body into two or more identical individuals - while the worms that stayed on Earth didn't.

The researchers think this may be due to temperature variation experienced by the space worms.

When the space worms returned, both the space and stay-at-home groups were transferred to petri dishes containing fresh spring water.

While the stay-at-home worms exhibited normal behavior, the 10 whole worms that had spent a month in space curled up and were partially paralyzed and immobile - taking two hours to return to normal.

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

(A) Worms returned from space were amputated into three fragments on Earth. Approximately 1/3 of the anterior part of the worm was cut off to create the head (panel B), then the posterior half was cut in half to create the pharynx (panel C) and tail fragments (panel D)

Space and stay-at-home worms also differed in their reaction to light.

Twenty months after returning to Earth, individuals from each group were placed in an arena, half of which was illuminated with red light, which the worms can't see, and half of which was illuminated with blue light.

An automated behavior analysis device revealed that space worms spent 70.5 percent of their time in the dark while the Earth-based worms spent 95.5 percent of their time in the dark.

Researchers also analyzed the microbiome of the worms and determined that there was a significant difference between the bacterial communities of space worms when compared to the control group.

By analyzing the chemical composition of the water in which the worms lived during the experiment, the researchers determined that exposure to space induces distinct differences in metabolism.

(A) Earth-only control worms exhibit full extension and rapid movement in a petri dish with water (B) Close-up of the Earth-only worms. (C) Space-exposed worms in state of water shock, ventrally curled and not moving. (D) Close-up of space-exposed worm

However, the researchers said that their experiments faced a number of unavoidable limitations.

For the Earth-based control group, it was difficult to match the temperatures experienced by worms in space over the course of the mission.

Future missions will use real-time data from space to fine-tune temperatures experienced by the controls on Earth.

The stress caused by liftoff and splashdown wasn't replicated in the control worms, although future experiments will aim to do so.

Another issues was that the amputation of worms was done on Earth, a requirement of protocols on the mission, but ideally, it would be done on the space station, and researchers hope that an ISS astronaut will be willing to conduct these experiments aboard the space station in the future.

The researchers intend for their work to help establish protocols for performing flat planarian research in space by determining ideal transfer logistics and conditions for future missions.



