Jess Thomson in Newsweek:
A strange, immortal tube-shaped animal has been discovered to regenerate a whole new body from only its mouth to avoid getting old. This creature, named Hydractinia symbiolongicarpus, a tiny invertebrate that lives on the shells of crabs, is usually immune to aging altogether, but was found to use aging within its body to grow an entirely new body, a study published in the journal Cell Reports found.
…Hydractinia had previously been found to have special stem cells that it used for regenerating its tissues. These stem cells are capable of transforming—differentiating—into any type of body cell, which more specialized cells like heart tissue or muscle tissue cannot do. This makes them capable of growing new body parts; humans can only use stem cells during development, but animals like Hydractinia can use stem cells throughout their lifetimes, making them functionally immortal. The researchers found that while Hydractinia stores its stem cells in the lower half of its body, but when they cut off its mouth, the mouth grew a whole new body, indicating that the animal could generate new stem cells. To investigate how these stem cells are triggered to generate, the authors described in the paper how they scanned the genome of Hydractinia for genes related to aging or “senescence”—lagging of cell repair and the aging of the body and its systems.
More here.