In a recent study published in the Proceedings of the National Academy of Scientists, marine biologists have discovered that the moon jellyfish rearranges existing body parts post amputation and recovers radial symmetry within a few days.
There are many sea creatures includes some species of jellyfish that have the ability to regenerate tissues after injury, the trait being vital for their survival.
The authors of the new study – Prof Lea Goentoro from the California Institute of Technology and her colleagues from the University of Oxford, UK, and Institute of Physics in Taipei City, Taiwan – wanted to know if the moon jellyfish would respond to injuries in the same manner as an injured hydra.
They concentrated their study on the jellyfish’s early stages because of its simple body plan which consists of a disk-shaped body with eight symmetrical arms which would make any regeneration of tissue clearly visible.
For simulating the injury amputations were done on anesthetized juvenile jellyfish, producing animals with 2 to 7 arms, rather than the usual eight. They then returned the jellyfish to their artificial seawater and examined the tissue response.
As expected, the wounds healed, but as the tissue around the cut was closing up in a few hours, they saw something quite strange, the jellyfish were not regenerating the tissue to replace the lost arm.
On the contrary, the jellyfish had reorganized its existing arms to be symmetrical and evenly spaced around the animal’s disk-like body.
“In response to arm amputation, the young jellyfish rearrange their remaining arms, recenter their manubria, and rebuild their muscular networks, all completed within 12 hours to 4 days. We call this process symmetrization,” the scientists wrote in the paper.
“We find that symmetrization is not driven by external cues, cell proliferation, cell death, and proceeded even when foreign arms were grafted on. Instead, we find that forces generated by the muscular network are essential. Inhibiting pulsation using muscle relaxants completely, and reversibly, blocked symmetrization.”
“Furthermore, we observed that decreasing pulse frequency using muscle relaxants slowed symmetrization, whereas increasing pulse frequency by lowering the magnesium concentration in seawater accelerated symmetrization.”
“In addition to adding to our understanding about self-repair mechanisms, the discovery could help engineers design new biomaterials,” Prof Goentoro said.
“Symmetrization may provide a new avenue for thinking about biomaterials that could be designed to heal by regaining functional geometry rather than regenerating precise shapes. Other self-repair mechanisms require cell proliferation and cell death – biological processes that aren’t easily translated to technology. But we can more easily apply mechanical forces to a material.”