Scientists have identified the mechanism that allows jellyfish to regain their symmetry after being injured.
A team of researchers performed amputations on anesthetized ephyra (juvenile) moon jellyfish, creating animals with less arms than the usual eight, California Institute of Technology reported. To the researchers surprise, the jellyfish did not regenerate to replace the missing arms, but rather reorganized their existing arms to regain symmetry.
"This is a different strategy of self-repair," Caltech assistant professor of biology Lea Goentoro said. "Some animals just heal their wounds, other animals regenerate what is lost, but the moon jelly ephyrae don't regenerate their lost limbs. They heal the wound, but then they reorganize to regain symmetry."
The researchers believe this survival technique mat be necessary for the jellyfish's movement, which also moves water and food past their mouths.
"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," Goentoro said.
The researchers found the jellyfish were not making or killing existing cells in response to the injuries, but instead used mechanical force from their own muscle contractions to create the symmetrization.
"Symmetrization is a combination of the mechanical forces created by the muscle contractions and the viscoelastic jellyfish body material," said graduate student Michael Abrams. "The cycle of contraction and the viscoelastic response from the jellyfish tissues leads to reorganization of the body. You can imagine that in the absence of symmetry, the mechanical forces are unbalanced, but over time, as the body and arms reorganize, the forces rebalance."
The discovery could help engineers design new biomaterials that "heal" themselves by regaining functional geometry instead of 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," Goentoro said.
The findings were reported in a recent edition of the journal Proceedings of the National Academy of Sciences (PNAS).
