The restoration of a lost arm in starfish occurs through regeneration.
Starfish are marine invertebrates having star-shaped bodies with arms radiating outside.
These sea creatures have the ability to restore a broken limb or body part. Their body possesses specialised cells called stem cells which make new cells to restore the lost body part.
This process by which an organism restores its broken or missing body parts is known as regeneration.
The process of regeneration mostly occurs in invertebrates.