Sea Life: Self-Healing, Symmetrization, and Reorganization

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The moon jellyfish has superpowers – but it’s not a comic book character! Image by ToniLynMuller

Many famous superheroes have the magnificent ability to heal themselves when attacked by their opponents. For instance, Deadpool’s ability to regenerate helps him to recuperate from almost any injury including broken bones, gunshot wounds, and even a missing hand, which grew back overnight.

This amazing ability to regrow limbs is pure fantasy for humans, but it’s reality for the moon jellyfish, which has been proven to self-heal in a unique way.

Scientists Michael Abrams and Lea Goentoro of the California Institute of Technology reported in Zoology that moon jellyfish (Aurelia aurita) use their remaining body parts to self-heal and regain function.

Self-healing Superpower

All animals have innate ability to self-heal, but not in the same manner, or to the same degree. According to an article in the science section of Forbes, the human liver can repair itself. Some lizards can regrow their tails.

Other species exhibit more advanced ability to self-heal such as the salamanders. They can grow back an entire limb, or even restore vital internal organs of their body such as the heart or brain.

Planarians, a class of flatworms, are also known as masters of self-healing because of their ability to rebuild any part of their bodies after amputation.

Scientists have also observed ocean organisms’ ability to self-heal as well. Abbe Trembley observed the regeneration capabilities of fresh water polyp, hydra as early as 1740, as reported by Morgan in 1901. This early scientist injured the organisms and observed their recovery. His discoveries led more scientists to study the regeneration mechanisms of animals.

Spotlight on Moon Jellyfish

In a more recent study conducted by Abrams and Goentoro, the researchers observed the self-healing mechanisms of young moon jellyfish called ephyra. At this stage, the jellyfish is about 3-5mm in diameter, with eight arms distributed evenly around its disc-shaped body.

This body design is vital for making vortices in the water that will drive the food towards it. The jellyfish eats plankton such as mollusks, crustaceans, tunicate larvae, copepods, rotifers, nematodes, young polychaetes, protozoans, and diatoms through filter feeding. When an ephyra grows into a medusa, tissues form between each arm.

Abrams and Goentoro used the same method used by Trembley. They amputated arms of ephyrae and observed their response. Unlike the salamanders, the young jellyfish did not regenerate new arms. Instead, the ephyrae reorganized their existing appendages to regain the balanced distribution of their arms. This mechanism of reorganization is called symmetrization.

The researchers were also surprised that the process of self-healing happened in less than two days in 90% of the total number of amputated ephyrae. Those with larger arms left in the body after amputation took a longer time to recover because the remaining part was initially broken down before symmetrisation started.

Another surprising finding in the study was the mechanism that drives symmetrization in moon jellyfish. Other organisms regenerate the missing body parts through cellular processes such as cellular proliferation or cell death. In moon jellyfish, self-healing is driven by mechanical forces generated by the propulsion machinery. When the ephyrae were inhibited from moving their arms, symmetrization fails to take place. The researchers simulated this process using a mathematical model and confirmed that the rate of muscle movement also governs how fast the symmetrization occurs. Thus, the same machinery that drives feeding also drives self-repair.

Symmetrization Caught in the Act

Young sea nettle (Chrysaora pacifica), Mediterranean jellyfish (Mastigias sp.), and fried egg jellyfish (Cotylorhiza tuberculata) also exhibited evidence of symmetrization as observed by the researchers. Symmetrization was also reported in other marine invertebrates. According to Hargitt, some hydromedusae “recast themselves into a morphological equivalent of their original form.”

Coonfield also saw the same behavior in ctenophores. Zirpolo reported sea stars that lost an arm to self-repair and “resemble a nearly perfect four-armed specimen.

These organisms have diverse body forms, tissue compositions, and movement machineries, indicating that symmetrization occurs in various ways in different organisms.

Symmetrization and Regeneration

Some organisms such as Aurelia polyps have shown both symmetrization and regeneration abilities. This leaves scientists to ask several questions about these amazing abilities of marine animals:

Did symmetrization evolve together with regeneration, or are they conflicting abilities?

How frequently can an organism regenerate in one life stage, and then reorganize in another life stage?

How does their body choose between regenerating or reorganizing?

These puzzles remain unanswered until scientists uncover the more truths behind marine organisms’ self-healing abilities.

 

 

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