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