Jellyfish restore the body 04.07.2015

All living beings have the ability to regenerate, it’s just that for some it is expressed to a lesser extent (for example, we cannot grow a finger or a leg to replace the lost ones), for someone it is more (for newts, for example, to restore a leg , eye or some internal organ is not a problem at all). Champions of self-healing can be called coelenterates - hydras, jellyfish and their relatives, although here it should still be remembered that they are much simpler than the same newts. In studies of regeneration, one of the most frequent model objects is the freshwater hydra from a biology textbook, which, after any injury, after any damage, can do everything as it was.

But, as it turned out, coelenterates do not always "do everything as it was." Michael Abrams (Michael Abrams) and his colleagues from the California Institute of Technology experimented with larvae-ethers of the jellyfish Aurelia eared. Ethers are simpler than adult jellyfish: a small disc-shaped body with 8 double outgrowth lobes at the edges, no tentacles as such, the digestive system is underdeveloped. One or more "arms" - blades were cut off from the larva, after which it healed the wound rather quickly, in a few hours. However, a new blade did not appear to replace the lost one. Instead, the ether rebuilt the body so as to become symmetrical again - regardless of how many "arms" were left for her, seven, five, or just two.

As you know, jellyfish are radially symmetrical animals: they can distinguish the upper part of the body from the lower, but it is impossible to separate the left side from the right. When moving, the jellyfish “slams” its dome and oral lobes (and the larva with the lobes located along the edges of the body), and it is the symmetry in its own structure that allows animals to move in the right direction. If any of the "limbs" is missing, then due to the resulting empty space, hydrodynamics will be disturbed, the water flows will go the wrong way when pushed, and the jellyfish will not be able to control its movements. Therefore, it turns out to be more important for the larva not so much to re-grow the lost lobe as to restore the symmetrical structure of the body. Moreover, asymmetric ether quite often, in 15% of cases, could not turn into an adult jellyfish at all.

In an article in PNAS, the authors write that the body of the larvae was rebuilt by muscular efforts: if a substance that relaxes muscle cells was added to the water where they lived, then symmetrization occurred much more slowly. On the contrary, if the ether muscles under the influence of an increased concentration of magnesium salts began to contract faster, then the symmetrical structure was restored more quickly.

Obviously, the whole point here is that due to the loss of the blades, the mechanical forces in the body of the jellyfish turned out to be unbalanced, which naturally led to a restructuring of the elastic body. At the same time, ethers did without stimulating active cell division and death, as it happens in regenerative processes in other animals - obviously, an acceptable result can be achieved mechanically here without high energy costs for cellular dynamics. Larvae of other species of jellyfish also turned out to be capable of symmetrization - of course, it would be interesting to find out whether adult jellyfish and other radially symmetrical organisms are capable of such a trick.

The results obtained once again tell us that morphogenesis is the formation of body parts, organs, etc. - depends not only on molecular genetic processes, but also on purely physical interactions between different parts of the body. It is known that human cells also sensitively react to mechanical forces, which can sometimes have a decisive influence on their cellular fate; it is possible that in the medical regeneration of our tissues and organs, more success can be achieved if we pay attention to their "physics".