The stone canal is membranous and is not calcified. (ii) The original function of water-vascular systems was feeding, not locomotion. Reproduction – Dioecious animals , Reproduction is sexual. The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. The podia also function in gas exchange and sensory reception. 8. Sexes are separate. Excretory system – absent. An excretory system is absent. Each radial canal gives a branch to the buccal podia and terminates as the lumen of the terminal tentacle. Fertilisation – usually external. Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side. The main ring canal bears five small inter-radial Tiedemann’s bodies. 10. (5) Water enters the Water Vascular System through a madreporite. 4. (4)It works like hydraulic system. Sub Phylum: Echinozoa. 11. Tube feet (podia) participate in locomotion, gas … (6) When the muscles in the tube feet contract the tube … Radially symmetrical, globoid or discoid without arms or brachioles. Helps in locomotion, capture and transport of food and respiration. Fig: Asterias and Ophiura. Water Vascular System of Echinus: The water vascular system is fundamen­tally similar to that of Asterias. Digestive system – complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side. Hemal system. Developed coelom and have a water driven tube system (water vascular system). (iii) In open type of circulatory system, the blood is pumped out of the heart and the cells and tissues are directly bathed in it. 7. Water vascular system – distinctive feature. (ii) The digestive system in Platyhelminthes has only a single opening to the outside of the body that serve as both mouth and anus, and is hence called complete. The visual system of starfish. Echinoderm - Echinoderm - Form and function of external features: Echinoderms have a skeleton composed of numerous plates of mineral calcium carbonate (calcite). Tube feet for locomotion and have regeneration capacity. Locomotion: Water vascular system with podia and tube-feet madreporite mostly present. Madriporite and anus remain on the aboral surface. Above: a transverse (cross) section through the arm of the brittlestar Ophiura. The water vascular system is a unique and defining characteristic of echinoderms. It is a vital part of the system and exhibits control over the hundreds to thousands of tube feet that live in the ambulacral grooves. Alimentary canal: Straight or coiled. It uses hydraulic pressure and the action of muscles to operate the various podia (Brusca and Brusca 1990). 7. (iii) The water-vascular system has soft membranes. ... For example, Ophiura. Functions of the water vascular system (i) The water-vascular system is chiefly used for locomotion. 9. Reproduction: Sexual and gonochoristic. (B) The arm tip of the crown-of-thorns starfish, A. planci showing a similar arrangement as for Culcita novaguineae. The most distinctive feature of echinoderms is the presence of water vascular system which helps in locomotion, capture and transport of food and respiration. Circulatory system: Perihaemel blood vascular system. Podia include both tube feet (used in locomotion and attachment) and tentacles (used in feeding). It allows diffusion of respiratory and nitrogenous wastes across the body wall. Body coelom: Enterocoelic type includes perivisceral coelom and water vascular cavities. The water vascular system is a complex network of canals and reservoirs. (A) The distal part of the ambulaccecral grove of the cushion star, Culcita novaguineae, showing the distalmost tube foot (DmTF) holding the eye and the putative sensory tube feet (white arrows). 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