What is the primary function of the water vascular system in echinoderms, such as starfish?

The correct option is Locomotion and feeding.

The water vascular system (also known as the ambulacral system) is a unique, complex hydraulic system found exclusively in echinoderms, such as starfish, sea urchins, and sea cucumbers.

Key Functions of the Water Vascular System:

1. Locomotion: Water enters through a sieve-like structure called the madreporite and circulates through a network of canals to tube feet (podia). By contracting muscles to alter water pressure inside these tube feet, the echinoderm can extend, adhere to surfaces, and retract them, allowing smooth movement across the ocean floor.

2. Feeding and Food Capture: The suction force generated by the tube feet enables starfish to grip, pull open, and capture prey, such as bivalves (clams and mussels).

While the water vascular system also plays secondary roles in gas exchange and waste removal, its primary functions are locomotion and feeding.