Starfish Can Regenerate Entire Limbs

The remarkable ability of a starfish to grow a new arm stems from its unique anatomy and cellular capabilities. Unlike many other animals, a starfish houses parts of its vital organs in each of its arms. This decentralized structure means that the loss of a limb is not necessarily fatal. Furthermore, starfish retain specialized, unassigned cells throughout their lives that are similar to stem cells. These cells can multiply and transform into any type of tissue required, from skin to nerve cells, forming a structure called a blastema at the site of the injury which serves as the foundation (Review) for the new limb.

This regenerative process unfolds in several stages, beginning with the rapid healing of the wound to prevent infection. Over a period that can last from several months to a year, the new arm gradually reforms, complete with muscles, nerves, and the tube feet it uses for movement. While most starfish species require at least a portion of the central body disc to be intact to regrow a limb, a few can accomplish the even more incredible feat of regenerating an entirely new body from a single severed arm.

Starfish don't only regenerate due to accidental injury; they can intentionally shed an arm to escape the grasp of a predator (Review), a defense mechanism known as autotomy. Some species also use this ability for asexual reproduction, breaking apart to form two new individuals. Historically, fishermen attempting to eliminate starfish by cutting them in half were often just doubling the population. This incredible capacity for regeneration has made the starfish a key model organism for scientists studying how to improve the repair of damaged tissues in humans.