The moon jellyfish has a particular self-healing strategy and so it manages to survive the bites of its much larger predators through rearranging its body.
This amazing self-healing strategy can be witnessed in its juvenile stage, which is called an ephyra and looks like a snowflake or a flower. It has eight legs that are disposed in radial symmetry. This means that they are placed at the same distance one from the other and at the same angle from the center portion.
The ephyrae are basically defenseless in the face of their predators, that include sea turtles that often leave them with bites and severed limbs. And this is where the interesting part begins.
By studying the physiology of Aurelia aurita, known as the moon jellyfish, and its self-repairing abilities, California Institute of Technology (Caltech) graduate student Michael Abrams has observed that the priority of the ephyrae is not to regrow their limbs, as would be expected, but to regain the radial symmetry that has been lost through the amputation of the limb or limbs.
It appears that their survival is dependent on this symmetrical disposition and so, the small snowflake-like ephyrae will start to rearrange the structure of their bodies, in order regain a proper position for their survival.
This is what Michael Abrams studied further alongside his scientific adviser, Lea Goentoro, Caltech biology professor. And so, they started amputating one to several limbs from the ephyrae, while they were anesthetized, so that they could see how they manage to rearrange their bodies and how this setback affects their evolution in adulthood.
Their research revealed that between 72 and 96% percent of the ephyrae that had their limbs amputated managed to regain radial symmetry, in accordance to how many limbs had been amputated.
Then, these ephyrae were studied closely as they sprouted into adulthood. Those who regained symmetry developed into weaker adults, with fewer tentacles and stomachs than a normal adult has, again according to how many limbs were severed.
However, those who did not manage to rearrange their limbs into a symmetrical disposition, grew up to be practically deformed. They had large mouths, but very small stomachs, and this combination did not make for a successful outcome in the environment.
After establishing the importance of the rearranging process, the team of scientists wanted to comprehend the physiology of the rearranging process. Initially, they thought that either new cells were being produced on one side of the ephyra, so that the limbs would travel towards the empty part, or that a group of cells was destroyed, in order to get to the symmetrical distribution.
When they treated the ephyrae so that their cells could neither reproduce nor die, it seems that they still managed to complete the rearranging sequence. And so they decided to test out other theories.
They decided to tackle the issue from the opposite side and completely anesthetized the ephyrae, so that they could not move at all. And this was the key moment in their study, because they saw that if the ephyrae were unable to move, than they were unable to rearrange their limbs as well.
It seems that the activity conducted by the muscles during the pulsation movements is what enables them to move their remaining legs into a symmetrical disposition and survive.
“It’s kind of beautiful that their normal swimming and feeding process leads to this self-repair. It’s normal,” said Michael Abrams.
This interesting discovery has broadened the horizons of self-repair mechanisms and could constitute an interesting model for a technological invention that might mimic the behavior of the moon jellyfish. The Caltech study was published this week in the scientific journal Proceedings of the National Academy of Sciences.
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