Self-repair is mechanism to heal wound fully by generation of new cell or tissues. This definition of self-repair is added by algorithm to regain symmetry. Self-repair is extremely important for living things. For example, when we get a cut on our finger and our skin can make new cells to heal the wound; losing tail — if in case of a particular kind of lizard — and tissue regeneration may produce a new one. Now, coming up new self-repair mechanism — the reorganization of existing anatomy to regain symmetry — in a certain species of jellyfish.

Many marine animals, including some jellyfish, can rapidly regenerate tissues in response to injury, and this trait is important for survival. If a sea turtle takes a bite out of a jellyfish, the injured animal can quickly grow new cells to replace the lost tissue. In fact, a jellyfish-like animal called the hydra is a very commonly used model organism in studies of regeneration.

But researchers were interested in another organism, the moon jellyfish (scientific name: Aurelia aurita). Researchers were interested to know repairing system of all species of jellyfish. They conducted observed study to check similarity of all the species. They came across moon jellyfish and wanted to know if the moon jellyfish would respond to injuries in the same manner as an injured hydra. The team focused their study on the jellyfish’s juvenile, or ephyra, stage, because the ephyra’s simple body plan — a disk-shaped body with eight symmetrical arms — would make any tissue regeneration clearly visible.

To simulate injury — like that caused by a predator in the wild — the team performed amputations on anesthetized ephyra, producing animals with two, three, four, five, six, or seven arms, rather than the usual eight. They then returned the jellyfish to their habitat of artificial seawater, and monitored the tissue response.

Although wounds healed up as expected, with the tissue around the cut closing up in just a few hours, the researchers noticed something unexpected: the jellyfish were not regenerating tissues to replace the lost arms. Instead, within the first two days after the injury, the ephyra had reorganized its existing arms to be symmetrical and evenly spaced around the animal’s disklike body. This so-called resymmetrization occurred whether the animal had as few as two limbs remaining or as many as seven, and the process was observed in three additional species of jellyfish ephyra.

This is a different strategy of self-repair. 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.

There are several reasons why symmetry might be more important to the developing jellyfish than regenerating a lost limb. Jellyfish and many other marine animals such as sea urchins, sea stars, and sea anemones have what is known as radial symmetry. Although the bodies of these animals have a distinct top and bottom, they do not have distinguishable left and right sides — an arrangement, present in humans and other higher life forms, known as bilateral symmetry. And this radial symmetry is essential to how the jellyfish moves and eats.

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

Thus maintaining symmetry appears to be vital not just for propulsion and but also for feeding. In the few cases when the injured animals do not symmetrize — the unsymmetrical ephyra also cannot develop into normal adult jellyfish, called medusa.

The researchers next wanted to figure out how the new self-repair mechanism works. Cell proliferation and cell death are commonly involved in tissue regeneration and injury response, but, the team found, the amputee jellyfish were neither making new cells nor killing existing cells as they redistributed their existing arms around their bodies.

Instead, the mechanical forces created by the jellyfish’s own muscle contractions were essential for symmetrization. In fact, when muscle relaxants were added to the seawater surrounding an injured jellyfish, slowing the animal’s muscle contractions, the symmetrization of the intact arms also was slowed down. In contrast, a reduction in the amount of magnesium in the artificial seawater speed up the rate at which the jellyfish pulsed their muscles, and these faster muscle contractions increased the symmetrization rate.

Symmetrization is a combination of the mechanical forces created by the muscle contractions and the viscoelastic jellyfish body material. The cycle of contraction and the viscoelastic response from the jellyfish tissues leads to reorganization of the body. It can be imagined that in the absence of symmetry, the mechanical forces will be unbalance, but over time, as the body and arms reorganize, the forces rebalance.

The discovery of self-repair could help engineers to design new 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. Other self-repair mechanisms require cell proliferation and cell death–biological processes that aren’t easily translated to technology. But researchers can more easily apply mechanical forces to a material.