Role of the water vascular system in Echinoderms is :

A.Respiration and Locomotion

B.Excretion and Locomotion

C.Capture and transport of food
D. Digestion and Respiration
E.Digestion and Excretion

Choose the correct answer from the options given below :

The correct answer is A and C Only.

The water vascular system is a distinctive hydraulic network found in echinoderms. It consists of a central ring canal, radial canals extending along each arm (or body side), and numerous tube feet that protrude through ampullae.

1. Locomotion: The tube feet operate by hydraulic pressure. When the ampulla contracts, fluid is forced into the tube foot, causing it to extend and attach to the substrate. Relaxation of the tube foot then pulls the body forward. This mechanism enables crawling, climbing, and even burrowing, making locomotion a primary function of the system.

2. Respiration: Many echinoderms exchange gases directly through their tube feet and the dermal surface of the water vascular system. The constant flow of seawater through the canals brings oxygenated water in contact with thin-walled tube feet, allowing diffusion of O₂ into the body and CO₂ out of it. Thus respiration is a second key role.

3. Capture and transport of food: The tube feet can grasp particles or prey and draw them toward the mouth. In species such as sea stars, the tube feet help position the prey and create a feeding tube that transports the food to the central disc where digestion begins.

Combining these functions, the water vascular system serves both respiration and locomotion (Option A) and capture and transport of food (Option C). No other listed pairs (B, D, or E) describe the primary functions of this system.

Therefore, the only correct combination is A and C Only.