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Jellyfish Shift Their Arms Around to Compensate for Lost Limbs

posted: 06/16/15
by: Danny Clemens
Moon jellyfish in the water. Aurelia aurita. Monterey Bay, California.
Jeff Foott/DCL

For many species of jellyfish, having a bite taken out of one's self isn't a big deal: the jellyfish are equipped with excellent self-repair mechanisms that quickly regenerate lost tissue, leaving the jellyfish as good as new.

For moon jellyfish, however, the self-repair process is a bit different, according to a new study from Caltech. Instead of focusing on replacing lost tissue, a moon jelly is more concerned with restoring symmetry to its off-kilter body after losing its limbs.

Caltech researchers performed a surgical amputation on an anesthetized jellyfish that had eight arms, creating a jelly with three arms and another with five. Unsurprisingly, each jelly's surgical wounds healed quickly, within a matter of hours.

However, researchers were surprised to see that, over the next 48 hours, the two newly created jellies were able to shift their limbs around their body, restoring balance to each side. Whereas they had anticipated eventually ending up with two eight-armed jellies, the researchers actually ended up with a three-armed jelly and a five-armed jelly, both of whose arms were evenly distributed across its body.

According to Caltech graduate student Michael Abrams, who helped pen a study in the journal Proceedings of the National Academy of Sciences about the jellies, the jellies' need for bodily symmetry is a survival tactic:

"Jellyfish move by 'flapping' their arms; this allows for propulsion through the water, which also moves water--and food--past the mouth," he says. "As they are swimming, a boundary layer of viscous--that is, thick--fluid forms between their arms, creating a continuous paddling surface. And you can imagine how this paddling surface would be disturbed if you have a big gap between the arms."

Abrams and his colleagues hope that their research could be applied to the development of self-replicating biomaterials.

"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," adds study lead author Lea Geontoro.

Click here to read the full study in Proceedings of the National Academy of Sciences

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