Did you know? If you cut a starfish, it won’t bleed – it doesn’t have blood! Rather, they circulate nutrients by using seawater in their vascular system.

Starfish, also known as sea stars, are fascinating creatures that have a unique ability to regrow their limbs if they lose them. Many people are unaware of the fact that starfish don’t have blood, which makes them quite different from other animals. This is one of the reasons why cutting a starfish won’t cause it to bleed.

Instead of blood, starfish have a unique circulatory system that uses seawater to circulate nutrients throughout their body. This system is known as the water vascular system and it is made up of a network of fluid-filled canals. The canals are connected to a series of tube feet that starfish use to move around and capture prey.

The water vascular system is composed of several parts, including the madreporite, stone canal, ring canal, radial canals, and tube feet. The system works by seawater entering the madreporite, a small plate on the top of the starfish, and then flowing into the stone canal. From there, it travels into the ring canal, which is the main hub of the system. The ring canal is then connected to five radial canals, which extend into each arm of the starfish. The radial canals are responsible for supplying the tube feet with seawater, which they use to move and capture prey.

One interesting thing about starfish is that they can regulate the amount of seawater in their water vascular system. This allows them to control their buoyancy and maintain their position in the water. If they need to float, they can increase the amount of seawater in their system, and if they need to sink, they can decrease it.

Another fascinating aspect of the water vascular system is that it is able to transport nutrients throughout the starfish’s body. The tube feet not only help with movement, but they are also used to capture prey and bring it to the mouth. Once the food is inside the starfish, the nutrients are absorbed and circulated throughout the body by the water vascular system.

In conclusion, starfish are incredible creatures that have a unique circulatory system. Although they don’t have blood, they are still able to circulate nutrients throughout their body using seawater. This is just one of the many fascinating things about these amazing creatures.