Prior to an important point in growth, the animal failed to close the wound created by cut, giving two fetal parts only to spill cells in the environment. To some extent, however, there was excellent existence, and the main part of the fetus could reproduce a tail section. This tells us that the normal signaling route present in the fetus is sufficient to pursue the process.
But at this stage the tail of the fetus is not able to rebuild its head. But researchers found that they could prevent WNT signaling in these back pieces, and it was enough to allow the head to develop.
Muscle deficiency
A possibility here is that WNT signaling is widely active in the back of the fetus at this point, blocking the formation of anterior structures. Alternatively, researchers envisage that the problem is accompanied by muscle cells that generally help organize the formation of a stem-cell-filled blastma, which is necessary to shut down the regeneration process. Since the anterior end of the fetus develops earlier, they suggest that the tail may not have enough muscle cells to kick this process in the early stages of development.
To test his hypothesis, he made some unusual experiments. He started by cutting the fetus's tail and saving them for 24 hours. At that point, they cut the front end from the tail, healing a new wound. At this point, the regeneration proceeded as normal, and the tail extended a new head. It is not a certain evidence that muscle cells are missing in the initial stages, but it indicates that the tail has some major developmental steps inside the 24-hour window after the first cut.
The results strengthen the idea that the upliftment of major body parts requires the re-establishment of signs that exclude the fetal organization in development-something that becomes complicated if those signs are currently working to organize the fetus. And it clearly shows that the cells required to perform this restructuring are not quickly separated in development, but rather some time. All that information will help clarify the big picture question how these animals manage such complex uplift process.
Current Biology, 2025. Doi: 10.1016/j.cub.2025.065 (about Dois).