Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 4 (2), 85-102
eCollection

Planarian Regeneration in Space: Persistent Anatomical, Behavioral, and Bacteriological Changes Induced by Space Travel

Affiliations

Planarian Regeneration in Space: Persistent Anatomical, Behavioral, and Bacteriological Changes Induced by Space Travel

Junji Morokuma et al. Regeneration (Oxf).

Abstract

Regeneration is regulated not only by chemical signals but also by physical processes, such as bioelectric gradients. How these may change in the absence of the normal gravitational and geomagnetic fields is largely unknown. Planarian flatworms were moved to the International Space Station for 5 weeks, immediately after removing their heads and tails. A control group in spring water remained on Earth. No manipulation of the planaria occurred while they were in orbit, and space-exposed worms were returned to our laboratory for analysis. One animal out of 15 regenerated into a double-headed phenotype-normally an extremely rare event. Remarkably, amputating this double-headed worm again, in plain water, resulted again in the double-headed phenotype. Moreover, even when tested 20 months after return to Earth, the space-exposed worms displayed significant quantitative differences in behavior and microbiome composition. These observations may have implications for human and animal space travelers, but could also elucidate how microgravity and hypomagnetic environments could be used to trigger desired morphological, neurological, physiological, and bacteriomic changes for various regenerative and bioengineering applications.

Keywords: planaria; regeneration; space travel.

Figures

Figure 1
Figure 1
Pre‐launch preparation and logistics. For logistics on Earth, live worm samples were secured inside the battery powered refrigerated shipping container iQ2 from Micro Q Technologies (Scottsdale, AZ, U.S.A.), and FedEx Space Solutions (Memphis, TN, U.S.A.) was utilized for rapid shipment of the iQ2 container. (A) iQ2, the proprietary battery operated precision‐temperature‐controlled shipping container. (B), (C) iQ2 inside the protective shipping exterior. (D) Manual worm amputation at Kennedy Space Center prior to launch. (E), (F) 50 mL conical tubes (blue caps) containing live worms were sealed, then secured in 3D‐printed custom retainers (yellow and purple), and placed inside the BRIC‐100VC containers (red) provided by NASA. (G) SpX‐5 SpaceX Dragon Spacecraft on top of the Falcon 9 rocket at Cape Canaveral SLC‐40 launch pad. (H) SpX‐5 liftoff on 10 January 2015, at 09:47 UTC. (I) SpX‐5 SpaceX Dragon Spacecraft in orbit prior to berthing with the ISS on 12 January 2015. Images reprinted with permission from Micro Q Technologies (A) and of SpaceX (G–I)
Figure 2
Figure 2
Flatworm amputation and space‐exposed and Earth‐bound worm sample schematics. (A) Approximately a third of the anterior part of the worm was cut off to create the head (H) fragment; then the posterior half was cut in half to create the pharynx (P) and tail (T) fragments, respectively. A total of 15 flatworms were cut and collected into three separate 50 mL conical tubes per fragment. (B) An identical number of worm samples, both whole and amputated fragments, were either sent into space or left on Earth for 32 days. (C) Immediately upon return to Earth, both space‐exposed and Earth‐only control worms from each sample tube were transferred to a Petri dish containing fresh Poland Spring water individually to identify any phenotypic changes
Figure 3
Figure 3
Water shock. (A), (B) Control worms left on Earth. (A) Representation of Earth‐only control worms, with full extension and rapid movement. (B) Close‐up image of representative Earth‐only control worm. (C), (D) Worms from space. (C) Representation of space‐exposed worms, in a state of water shock (ventrally curled and no movement). (D) Close‐up image of representative stocked space‐exposed worm (See also Videos S1 and S2.)
Figure 4
Figure 4
Double‐headed worm from space. (A) Schematic image of the original pharynx fragment, which traveled to space. (B) After return from space, one out of 15 pharynx fragments has regenerated into an extremely rare double‐headed worm. (C), (D) Close‐up images of each of the two regenerated heads
Figure 5
Figure 5
Amputation of double‐headed worm from space results in double‐headed morphology. (A) Schematics of amputation of the double‐headed space worm. (B) Double‐headed space worm before amputation at the dotted line; note that this photograph is the same as the image that appears in Figure 4B. (C) Double‐headed worm immediately after amputation of both heads. (D) Amputated double‐headed worm after 2 weeks of regeneration. Note that, while the two head fragments regenerated into two single‐headed worms like a normal worm, the head‐less fragment regenerated into a double‐headed worm. (E), (F) Close‐up images of each of the two regenerated heads of the re‐amputated double‐headed worm
Figure 6
Figure 6
Space‐exposed worms demonstrate more variable photophobic behavior than Earth‐only worms. (A) Earth‐only and space‐exposed planaria were placed individually in an automated behavior device which recorded animal location, speed, and response to light. (B) Overhead illumination is provided by LEDs which illuminate half the arena with red light (invisible to planaria) and half with blue light. (C) Space‐exposed worms demonstrated significant variability in their photo‐aversive behavior compared to Earth‐only worms (F test, p < 0.001). N = 6 for both treatments. Error bars indicate ± 1 SD. In dot plots in (C), the lateral positioning of the dots, within each of the two groups, is only to enable the separate data points to be distinguished from each other even when they occupy the same horizontal coordinate
Figure 7
Figure 7
Bacterial community composition of Earth‐only and space‐exposed D. japonica. (A) Relative abundance of culture‐based morphotypes detected across Earth‐only (n = 9) and space‐exposed (n = 10) worms. (B) Representative plates showing bacterial morphotypes and distinguishable differences between space‐exposed and Earth‐only worms

Similar articles

See all similar articles

Cited by 5 articles

References

    1. Adams D. S. (2008). A new tool for tissue engineers: ions as regulators of morphogenesis during development and regeneration. Tissue Engineering 14, 1461–1468. - PubMed
    1. Adams D. S., & Levin M. (2013). Endogenous voltage gradients as mediators of cell−cell communication: strategies for investigating bioelectrical signals during pattern formation. Cell and Tissue Research 352, 95–122. - PMC - PubMed
    1. Adell T., Salo E., van Loon J. J., & Auletta G. (2014). Planarians sense simulated microgravity and hypergravity. BioMed Research International 2014, 679672. - PMC - PubMed
    1. Antwis R. E., Preziosi R. F., Harrison X. A., & Garner T. W. (2015). Amphibian symbiotic bacteria do not show a universal ability to inhibit growth of the global panzootic lineage of Batrachochytrium dendrobatidis . Applied and Environmental Microbiology 81, 3706–3711. - PMC - PubMed
    1. Aoki R., Wake H., Sasaki H., & Agata K. (2009). Recording and spectrum analysis of the planarian electroencephalogram. Neuroscience 159, 908–914. - PubMed

LinkOut - more resources

Feedback