The Sea Star That Regrows Its Own Brain

Sea stars, often called starfish, are not fish. They are echinoderms, a group of animals named for their “spiny skin.” These ocean creatures have no blood and no central brain like humans do. Instead, a ring of nerves sits in the center of their body, connecting to nerve cords that run down each arm. This simple nervous system allows them to sense touch, light, and temperature in the water.

The Power of Regeneration

The most famous ability of the sea star is regeneration (regrowing body parts). If a predator grabs a sea star by the arm, the animal can detach that limb to escape. This defense is effective because the sea star can simply grow the missing arm back later.

For some species, the process is even more powerful. If a single severed arm contains a piece of the central disc (the middle circle of the body), it can grow four new arms and a new center. This means one sea star can effectively become two separate animals. This process is slow and requires a lot of energy, taking months or even a year to complete.

Tube Feet and Senses

The underside of a sea star is covered in hundreds of tiny, flexible tubes called tube feet. The sea star pumps seawater in and out of these feet to create suction. This hydraulic (water-pressure) system allows them to walk across rocks and grip prey tightly, such as clams and mussels.

At the very tip of each arm is a small red eye spot. These primitive eyes cannot see images like human eyes, but they can sense the difference between light and dark. This helps the sea star find safety in shadows or navigate toward reefs.