Question

Stone canal is a part of ______ structure of echinoderms.
A. Digestive
B. Respiratory
C. Water vascular
D. Excretory

Answer 1

Hint: The phylum Echinodermata has a stone canal that plays an important role in serving as a pump that drives the circulation of sea water. Echinoderms are triploblastic and have a spherical or elongated body. They are marine organisms.

Complete answer: The stone canal is a part of the structure of echinoderms. It is a part of the vascular system. In sea stars, water enters the water vascular system through a sieve-like structure on the upper surface of the animal. This sieve-like structure is called the madreporite. It lies over a small sac, also known as an ampulla. This ampulla is connected to a duct known as the stone canal. As the name implies, the stone canal has walls which are generally lined with calcareous material. The water vascular system is a hydraulic system present in echinoderms, such as sea stars and sea urchins, for locomotion, transportation of food and water and for respiration. This system is composed of canals which connect numerous tube feet. Locomotion in echinoderms is by alternate contraction of muscles that force the entry of water into the tube feet, making them extend and push against the ground followed by relaxation, which allows the feet to retract. The exact structure of this system varies between the five classes of echinoderms. The water vascular system is a part of the coelomic cavities of echinoderms, together with the haemal coelom (or haemal system), perivisceral coelom, gonadal coelom and perichaetial coelom.
Hence, the correct answer is option C.

Note: Other terms used to refer to the water vascular system are ambulacral system and aquiferous system. Echinoderms are triploblastic and have a coelomic cavity and their skeleton is made up of calcium carbonate.