Before a decisive point in evolution, the animals failed to close the wound made by the pieces, causing the fetal half to exit simply to the environment. Somewhat later, however, there was excellent survival, and the main part of the fetus can renew the tail part. This tells us that the regular signal paths in the fetus are sufficient to push the process forward.
But the fetus’s tail at this stage does not seem to be able to rebuild its head. But researchers found that they could prevent Wnt’s signals in these back shrapnel, and that was sufficient to allow the head to develop.
Lack of muscles
One of the possibilities here is that WNT signals are widely active in the back of the fetus at this stage, preventing the formation of the front structures. Instead, the researchers assume that the problem is with muscle cells that usually help regulate the formation of edema of sins filled with stem cells, which is needed to start the renewal process. Since the front end of the fetus develops early, they point out that there may be enough muscle cells in the tail to start this process in the early stages of development.
To test their hypothesis, they made a fairly unusual experience. They started cutting the fetal tails and rescuing them for 24 hours. At this point, they cut the front end of tails, and created a new wound to recover. At this stage, the renewal continued as usual, and tails grew a new head. This is not a final evidence that muscle cells are what is missing in the early stages, but it indicates that some of the main development step occurs in the tail inside the window 24 hours after the first pieces.
The results reinforce the idea that renewing the main body parts requires the re-establishment of signals that put the fetus’s organization in development-which becomes complicated if these signals are currently working to regulate the fetus. It clearly explains that the cells needed to do this reorganization do not set aside early in development, but instead it takes some time to appear. All this information will help clarify the biggest question about how to manage these animals for the complex renewal process.
Current biology, 2025. Doui: 10.1016/J.cub.2025.03.065 (About Dois).