Scientists study the ability of many species capable of regenerating parts of themselves, hoping that new medicine learned from these tricks could help humans with serious injuries. The star of the show to date has been the Axolotl, aka Mexican walking fish, which regrows more body parts than any other known species.
But a new champion has entered the scene, as scientists study crayfish, which continuously regenerate neurons in their sensitive smelling organs and exposed eyestalks. Studying the process, known as neurogenesis, in crayfish could help us understand how humans maintain their brain health, and where the process goes wrong.
Scientists found that crayfish have a natural circuit for harboring blood cells similar to our white blood cells in a 'nursery' where they are turned into neurons. The cells are converted to have properties of stem cells, which allows them to be reprogrammed to become neurons.
What surprised scientists in this discovery is the link between the immune system and the regeneration of neurons. The blood cells converted to neurons in crayfish, called hemocytes, are produced by the immune system, in a process that parallels the production of white blood cells that are the front-line troops of the human immune system. In the words of co-auther Dr. Irene Söderhäll, of Uppsala University in Sweden:
"Our findings in crayfish indicate that the immune system is intimately tied to mechanisms of adult neurogenesis, suggesting a much closer relationship between the immune system and nervous system than has been previously appreciated."
It is known that humans regenerate neurons in some parts of our brains throughout our lives, so understanding how this process works could lead to breakthroughs in treatment of degenerative brain diseases. This opens a whole new field of study into the impact of immunotherapy treatments on common illnesses, including depression.
Moreover, this represents a unique opportunity to get a closer look at the natural process of transdifferentiation -- that is, the way in which the body dictates which purpose a cell will serve. Knowing how to encourage cells to convert into other types of cells could help in the treatment of spinal column injuries, amputations, and other injuries.
It should serve to remind us as well, of the importance of the lessons we can learn from the many species around us, and the importance of preserving examples like the Axolotl, which was pronounce extinct in the wild after a study netted zero specimens (although eyewitness Axolotl reports indicate a few may survive). Some species of crayfish even make the list of 20 animals you didn't know are going extinct.