Question

Which of the following is not part of the echinoderm water vascular system?

• A. Ring canal
• B. Tube feet
• C. Radial canal
• D. Osculum

Answer 1

The correct option is D Osculum

All echinoderms have a water-vascular system, a set of water-filled canals branching from a ring canal that encircles the gut. Water enters (and leaves) the system through a sieve-like structure called madreporite, on the upper surface of the animal. The madreporite is united with the ring canal via a duct called the stone canal. The water is then separated into five radial canals which run outwards along the ambulacral grooves. The radial canals are made of double rows of small sacs called ampullae. Ampullae are connected to sucker-like podia. The ampulla and podium (singular) together make up the tube foot. The tube feet are sucker-like appendages that the echinoderm can use to move, grip the substrate, or manipulate objects. These tube feet are extended and retracted by hydraulic pressure in the water-vascular system. Osculum is part of the water canal system of sponges (Porifera).