Why can some worms reproduce by splitting into two pieces?

Some worms, such as planarian flatworms, can reproduce by splitting into pieces because they possess a remarkable capacity for regeneration. This process is a form of asexual reproduction where each separated portion of the body is capable of regrowing missing parts to become a complete, independent animal.12

The biological mechanism behind this ability involves:

• Blastema Formation: Following an injury or division, a mass of undifferentiated cells called a blastema forms at the wound site. These cells are capable of differentiating into various tissues, such as muscle, intestine, or brain tissue, depending on their location.34
• Cellular Potential: Researchers believe this process is driven by either undifferentiated reserve cells known as neoblasts—which are rich in RNA—or by specialized cells near the wound that dedifferentiate to regain the ability to form new structures.24
• Developmental Signaling: Regeneration occurs in a stepwise, organized fashion. The development of one part, such as the brain, often stimulates the production of subsequent structures like the pharynx, ensuring the new individual is fully functional.4

This ability allows these organisms to propagate efficiently, though it results in offspring that are genetically identical to the parent.5