Jellyfish Rearranges Its Arms to Recover From Amputation

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Justine Alford

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568 Jellyfish Rearranges Its Arms to Recover From Amputation
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While we may have the luxury of surgeons to put us back in one piece following injury, other members of the animal kingdom are not quite so fortunate (unless, of course, a vet happens to be around, but let’s not be pedantic). So what do they do? Healing is an obvious and ubiquitous ability, and some animals can regrow limbs should they lose them.

Limb regeneration may sound creepy to us, but it’s actually pretty common in invertebrate species, and some vertebrates like salamanders can also do it. But it turns out, there’s an even more weird and wonderful mechanism out there that had slipped under scientists’ radars until now. Rather than growing back a body part that has been lopped off, the moon jellyfish actually shuffles its existing body parts around in order to recover symmetry.


It was purely by accident that the researchers made this remarkable discovery. The team from Caltech had initially designed a study to examine limb repair in the immortal jellyfish (Turritopsis dohrnii), but their samples took a while to arrive. Rather than sitting idle, the scientists used this opportunity to have a run through of the techniques they were going to use, with the help of the common moon jellyfish (Aurelia aurita), National Geographic reports.

Since injury is reportedly common in marine invertebrates, and many possess the capacity to regenerate, the researchers were interested in how the jellyfish respond to injuries. Much to the researchers’ surprise, after performing an arm amputation on the test subject, the moon jellyfish did not regrow its limbs, but instead rearranged its existing body parts to regain symmetry. This is crucial for jellyfish since asymmetrical individuals would struggle to glide through the water efficiently.

Astonishingly, this reorganization process, which has been dubbed “symmetrization,” only took between 12 hours to 4 days to complete, the team reports in Proceedings of the National Academy of Sciences. Further examination revealed that this ability was not driven by cell growth, death or external cues, and even took place when the researchers grafted foreign arms onto the amputated individual. Instead, it was found to be dependent on the muscle machinery the jellyfish uses to propel itself through the water.

When the team applied muscle relaxants to the amputees, they failed to undergo symmetrization. Similarly, when the researchers used drugs to rev up the pulsation rate of their muscles, the process was completed in a shorter period of time. As pointed out by National Geographic, this seems to suggest that the jellyfish contract their muscles in such a way that it forces the remaining arms further apart.


“It’s like squeezing one side of a stress ball and you get a protrusion on the other side,” lead researcher Lea Goentoro told National Geographic.

Moving forward, the researchers are optimistic that this discovery could ultimately serve as inspiration for a new generation of biomaterials, and possibly help researchers working in the field of regenerative medicine. 


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